Selected Quarterly Financial Data (Unaudited) - Restated Consolidated Statement of Cash Flows (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Jun. 30, 2016
Jun. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
OPERATING ACTIVITIES                          
Net income including non-controlling interests $ 6,134 [1] $ 7,671 [1] $ 5,953 [1] $ 6,974 [1] $ 7,957 [1] $ 5,293 [1] $ 13,624 [1] $ 13,250 [1] $ 19,758 [1] $ 20,224 [1] $ 26,268 $ 26,489 [1] $ 25,314 [1]
Adjustments to reconcile net income including non-controlling interests to net cash provided by operating activities: [Abstract]                          
Depreciation and amortization     2,091 [1]     1,807 [1] 4,158 [1] 3,674 [1] 6,210 [1] 5,656 [1] 8,779 7,952 [1] 6,740 [1]
Provision for doubtful accounts 917 [1] 956 [1] 1,089 [1] 1,067 [1] 1,062 [1] 990 [1] 2,045 [1] 2,052 [1] 2,962 [1] 3,119 [1] 4,040 4,170 [1] 4,112 [1]
Equity-based awards compensation expense     1,221 [1]     991 [1] 2,484 [1] 2,206 [1] 3,748 [1] 3,368 [1] 4,962 4,491 [1] 3,363 [1]
Loss on sale of fixed assets     (19) [1]     17 [1] 0 [1] (13) [1] 31 [1] 3 [1] 152 84 [1] 35 [1]
Excess tax benefit from equity-based awards     142 [1]     (271) [1] 0 [1] (430) [1] 0 [1] (816) [1] 0 (947) [1] (948) [1]
Deferred income tax     1,823 [1]     473 [1] 2,503 [1] 2,056 [1] 3,238 [1] 2,918 [1] 2,979 5,953 [1] 5,106 [1]
Other     0 [1]     34 [1] 0 [1] 111 [1] 0 [1] 180 [1] 0 180 [1] 135 [1]
Changes in operating assets and liabilities: [Abstract]                          
Increase in patient accounts receivable     (2,185) [1]     (2,185) [1] (2,449) [1] (2,880) [1] (2,548) [1] (4,148) [1] (3,275) (5,519) [1] (5,388) [1]
(Increase) decrease in accounts receivable - other     43 [1]     125 [1] 53 [1] 165 [1] 116 [1] (145) [1] (400) (852) [1] 341 [1]
(Increase) decrease in other assets     (2,282) [1]     106 [1] (2,443) [1] (13) [1] (4,979) [1] (1,485) [1] (1,399) (1,375) [1] 1,155 [1]
Increase (decrease) in accounts payable and accrued expenses     3,392 [1]     (5,976) [1] 6,603 [1] (3,958) [1] 3,582 [1] (3,766) [1] 2,994 (7,011) [1] 1,868 [1]
Increase (decrease) in mandatorily redeemable non-controlling interests     2,578 [1]     406 [1] 4,028 [1] 90 [1] 5,372 [1] 683 [1] 5,598 2,509 [1] 2,936 [1]
(Decrease) increase in other liabilities     365 [1]     665 [1] 447 [1] 927 [1] 708 [1] 380 [1] 352 1,396 [1] (3,378) [1]
Net cash provided by operating activities     14,211 [1]     2,475 [1] 31,053 [1] 17,237 [1] 38,198 [1] 26,171 [1] 51,050 37,520 [1] 41,391 [1]
INVESTING ACTIVITIES [Abstract]                          
Purchase of fixed assets     (1,738) [1]     (1,419) [1] (3,453) [1] (2,873) [1] (5,620) [1] (4,690) [1] (8,260) (6,263) [1] (5,167) [1]
Purchase of businesses, net of cash acquired     (12,899) [1]     (6,445) [1] (12,958) [1] (14,467) [1] (12,958) [1] (14,434) [1] (23,623) (18,965) [1] (12,270) [1]
Acquisitions of non-controlling interests     (388) [1]     (359) [1] (250) [1] (968) [1] (664) [1] (942) [1] (670) (968) [1] (227) [1]
Proceeds on sale of fixed assets, net     42 [1]     8 [1] 42 [1] 72 [1] 42 [1] 71 [1] 61 71 [1] 47 [1]
Net cash used in investing activities     (14,983) [1]     (8,215) [1] (16,619) [1] (18,236) [1] (19,200) [1] (19,995) [1] (32,492) (26,125) [1] (17,617) [1]
FINANCING ACTIVITIES [Abstract]                          
Distributions to non-controlling interests     (1,113) [1]     (1,045) [1] (2,893) [1] (2,904) [1] (4,441) [1] (4,148) [1] (5,718) (5,892) [1] (5,963) [1]
Cash dividends to shareholders - funded     (2,125) [1]       (4,254) [1] (3,723) [1] (6,382) [1] (5,586) [1] (8,510) (7,449) [1] (5,873) [1]
Proceeds from revolving line of credit     49,000 [1]     34,000 [1] 93,000 [1] 51,000 [1] 128,000 [1] 75,000 [1] 168,000 103,000 [1] 134,300 [1]
Payments on revolving line of credit     (40,500) [1]     (27,000) [1] (94,500) [1] (44,500) [1] (136,000) [1] (63,500) [1] (166,000) (93,500) [1] (139,800) [1]
Payments to settle mandatorily redeemable non-controlling interests     (1,136) [1]       (1,136) [1]   (1,136) [1] (1,860) [1] (1,262) (6,115) [1] (5,233) [1]
Principal payments on notes payable     (250) [1]     (200) [1] (533) [1] (608) [1] (592) [1] (616) [1] (800) (884) [1] (825) [1]
Tax benefit from equity-based awards     323 [1]     271 [1] 556 [1] 430 [1] 798 [1] 816 [1] 0 947 [1] 948 [1]
Other     1 [1]       1 [1] 5 [1] 1 [1] 5 [1] 1 5 [1] 45 [1]
Net cash (used in) provided by financing activities     4,200 [1]     6,026 [1] (9,759) [1] (300) [1] (19,752) [1] 111 [1] (14,289) (9,888) [1] (22,401) [1]
Net increase in cash and cash equivalents     3,428 [1]     286 [1] 4,675 [1] (1,299) [1] (754) [1] 6,287 [1] 4,269 1,507 [1] 1,373 [1]
Cash and cash equivalents - beginning of period [1] 20,453 19,206 15,778 12,972 14,557 14,271 15,778 14,271 15,778 14,271 15,778 14,271 12,898
Cash and cash equivalents - end of period 15,024 [1] 20,453 [1] 19,206 [1] 20,558 [1] 12,972 [1] 14,557 [1] 20,453 [1] 12,972 [1] 15,024 [1] 20,558 [1] 20,047 15,778 [1] 14,271 [1]
Cash paid during the period for: [Abstract]                          
Income taxes     2,265 [1]     1,275 [1] 5,513 [1] 3,835 [1] 10,051 [1] 5,659 [1] 10,584 7,779 [1] 9,253 [1]
Interest     248 [1]     235 [1] 512 [1] 460 [1] 770 [1] 616 [1] 784 884 [1] 1,103 [1]
Non-cash investing and financing transactions during the period: [Abstract]                          
Purchase of business - seller financing portion     500 [1]     500 [1] 500 [1] 1,350 [1] 500 [1] 1,350 [1] 1,000 1,800 [1] 400 [1]
Acquisition of noncontrolling interest - seller financing portion     388 [1]       388 [1]   388 [1] 0 [1] 387 0 [1] 0 [1]
Payment to settle redeemable non-controlling interest - financing portion     126 [1]       126 [1]   126 [1] 1,240 [1] 127 3,077 [1] 67 [1]
Revaluation of mandatorily redeemable non-controlling interests [1]     2,191     244 0 196 6,056 697      
Receivable from sale of non-controlling interests             (148) [1]   (148) [1]   (138) 0 [1] 0 [1]
As Reported [Member]                          
OPERATING ACTIVITIES                          
Net income including non-controlling interests 7,972 10,060 7,680 8,064 9,117 6,151 17,740 15,268 25,712 23,332   31,691 30,424
Adjustments to reconcile net income including non-controlling interests to net cash provided by operating activities: [Abstract]                          
Depreciation and amortization     2,091     1,807 4,158 3,674 6,210 5,656      
Provision for doubtful accounts 917 956 1,089 1,067 1,062 990 2,045 2,052 2,962 3,119      
Equity-based awards compensation expense     1,221     991 2,484 2,206 3,748 3,368      
Loss on sale of fixed assets     (19)     17 0 (13) 31 3      
Excess tax benefit from equity-based awards     (323)     (271) (556) (430) (798) (816)      
Deferred income tax     2,709     565 4,170 2,130 5,688 3,181   7,001 6,275
Other     0     34 0 111 0 180      
Changes in operating assets and liabilities: [Abstract]                          
Increase in patient accounts receivable     (2,185)     (2,185) (2,449) (2,880) (2,548) (4,148)      
(Increase) decrease in accounts receivable - other     43     125 53 165 116 (145)      
(Increase) decrease in other assets     (2,282)     106 (2,443) (13) (4,979) (1,485)   (1,477) (2,493)
Increase (decrease) in accounts payable and accrued expenses     4,322     (5,976) 7,715 (3,958) 5,178 (3,766)   (7,013)  
Increase (decrease) in mandatorily redeemable non-controlling interests     0     0 0 0 0 0   0 0
(Decrease) increase in other liabilities     365     665 447 927 708 380   1,482 730
Net cash provided by operating activities     14,711     3,019 33,364 19,239 42,028 28,859   41,243 45,194
INVESTING ACTIVITIES [Abstract]                          
Purchase of fixed assets     (1,738)     (1,419) (3,453) (2,873) (5,620) (4,690)      
Purchase of businesses, net of cash acquired     (12,899)     (6,445) (12,958) (14,467) (12,958) (14,434)      
Acquisitions of non-controlling interests     (1,524)     (359) (1,386) (968) (1,800) (2,802)      
Proceeds on sale of fixed assets, net     42     8 42 72 42 71      
Net cash used in investing activities     (16,119)     (8,215) (17,755) (18,236) (20,336) (21,855)   (32,240) (22,880)
FINANCING ACTIVITIES [Abstract]                          
Distributions to non-controlling interests     (1,613)     (1,589) (5,204) (4,906) (8,271) (6,836)   0 0
Cash dividends to shareholders - funded     (2,125)       (4,254) (3,723) (6,382) (5,586)      
Proceeds from revolving line of credit     49,000     34,000 93,000 51,000 128,000 75,000      
Payments on revolving line of credit     (40,500)     (27,000) (94,500) (44,500) (136,000) (63,500)      
Payments to settle mandatorily redeemable non-controlling interests     0       0   0 0   0 0
Principal payments on notes payable     (250)     (200) (533) (608) (592) (616)      
Tax benefit from equity-based awards     323     271 556 430 798 816      
Other     1       1 5 1 5   22 222
Net cash (used in) provided by financing activities     4,836     5,482 (10,934) (2,302) (22,446) (717)   (7,496) (20,941)
Net increase in cash and cash equivalents     3,428     286 4,675 (1,299) (754) 6,287      
Cash and cash equivalents - beginning of period 20,453 19,206 15,778 12,972 14,557 14,271 15,778 14,271 15,778 14,271 15,778 14,271  
Cash and cash equivalents - end of period 15,024 20,453 19,206 20,558 12,972 14,557 20,453 12,972 15,024 20,558   15,778 14,271
Cash paid during the period for: [Abstract]                          
Income taxes     2,265     1,275 5,513 3,835 10,051 5,659      
Interest     248     235 512 460 770 616      
Non-cash investing and financing transactions during the period: [Abstract]                          
Purchase of business - seller financing portion     500     500 500 1,350 500 1,350      
Acquisition of noncontrolling interest - seller financing portion     514       514   514 1,240      
Payment to settle redeemable non-controlling interest - financing portion     0       0   0 0      
Revaluation of mandatorily redeemable non-controlling interests     0     0 0 627 0 627      
Receivable from sale of non-controlling interests             (148)   (148)        
Adjustment [Member]                          
OPERATING ACTIVITIES                          
Net income including non-controlling interests (1,838) (2,389) (1,727) (1,090) (1,160) (858) (4,116) (2,018) (5,954) (3,108)   (5,202) (5,110)
Adjustments to reconcile net income including non-controlling interests to net cash provided by operating activities: [Abstract]                          
Depreciation and amortization     0     0 0 0 0 0      
Provision for doubtful accounts 0 0 0 0 0 0 0 0 0 0      
Equity-based awards compensation expense     0     0 0 0 0 0      
Loss on sale of fixed assets     0     0 0 0 0 0      
Excess tax benefit from equity-based awards     465     0 556 0 798 0      
Deferred income tax     (886)     (92) (1,667) (74) (2,450) (263)   (1,048) (1,169)
Other     0     0 0 0 0 0      
Changes in operating assets and liabilities: [Abstract]                          
Increase in patient accounts receivable     0     0 0 0 0 0      
(Increase) decrease in accounts receivable - other     0     0 0 0 0 0      
(Increase) decrease in other assets     0     0 0 0 0 0   102 3,648
Increase (decrease) in accounts payable and accrued expenses     (930)     0 (1,112) 0 (1,596) 0   2  
Increase (decrease) in mandatorily redeemable non-controlling interests     2,578     406 4,028 90 5,372 683   2,509 2,936
(Decrease) increase in other liabilities     0     0 0 0 0 0   (86) (4,108)
Net cash provided by operating activities     (500)     (544) (2,311) (2,002) (3,830) (2,688)   (3,723) (3,803)
INVESTING ACTIVITIES [Abstract]                          
Purchase of fixed assets     0     0 0 0 0 0      
Purchase of businesses, net of cash acquired     0     0 0 0 0 0      
Acquisitions of non-controlling interests     1,136     0 1,136 0 1,136 1,860      
Proceeds on sale of fixed assets, net     0     0 0 0 0 0      
Net cash used in investing activities     1,136     0 1,136 0 1,136 1,860   6,115 5,263
FINANCING ACTIVITIES [Abstract]                          
Distributions to non-controlling interests     500     544 2,311 2,002 3,830 2,688   (5,892) (5,963)
Cash dividends to shareholders - funded     0       0 0 0 0      
Proceeds from revolving line of credit     0     0 0 0 0 0      
Payments on revolving line of credit     0     0 0 0 0 0      
Payments to settle mandatorily redeemable non-controlling interests     (1,136)       (1,136)   (1,136) (1,860)   (6,115) (5,233)
Principal payments on notes payable     0     0 0 0 0 0      
Tax benefit from equity-based awards     0     0 0 0 0 0      
Other     0       0 0 0 0   (17) (177)
Net cash (used in) provided by financing activities     (636)     544 1,175 2,002 2,694 828   (2,392) (1,460)
Net increase in cash and cash equivalents     0     0 0 0 0 0      
Cash and cash equivalents - beginning of period 0 0 0 0 0 0 0 0 0 0 $ 0 0  
Cash and cash equivalents - end of period $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0   $ 0 $ 0
[1] as restated