Note 17 - Segment Reporting - Reconciliation of Reportable Segment Revenue, Expenses and Profit (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Interest income $ 19,032 $ 18,836 $ 18,382 $ 18,313 $ 16,488 $ 13,450 $ 12,714 $ 12,193 $ 74,563 $ 54,845 $ 31,342
Interest expense 2,042 1,959 1,730 1,650 1,507 1,191 1,071 1,027 7,381 4,796 2,869
Net interest income 16,990 16,877 16,652 16,663 14,981 12,259 11,643 11,166 67,182 50,049 28,473
Provision for loan and lease losses 441 373 901 1,533 631 201 120 161 3,248 1,113 978
Noninterest income 3,472 4,002 3,357 3,125 2,298 2,353 2,206 1,764 13,956 8,459 5,032
Noninterest expense                 49,079 40,245 23,453
Earnings before income taxes 7,881 7,874 6,854 6,202 5,042 4,516 4,113 3,479 28,811 17,150 9,074
Income tax expense 2,600 2,639 2,072 2,083 1,667 1,453 1,264 1,092 9,394 5,476 3,159
Noncontrolling interest (374) (422) (428) (340) (437) (573) (593) (466) (1,564) (2,069) (512)
Net earnings attributable to National Commerce Corporation 4,907 $ 4,813 $ 4,354 $ 3,779 2,938 $ 2,490 $ 2,256 $ 1,921 17,853 9,605 5,403
Total assets 1,950,784       1,763,369       1,950,784 1,763,369 1,138,426
Operating Segments [Member] | Retail and Commercial Banking [Member]                      
Interest income                 64,256 44,072 27,144
Interest expense                 7,181 4,670 2,746
Net interest income                 57,075 39,402 24,398
Provision for loan and lease losses                 2,325 1,158 174
Noninterest income                 5,848 2,340 811
Noninterest expense                 37,280 29,741 18,048
Earnings before income taxes                 23,318 10,843 6,987
Income tax expense                 7,901 3,866 2,627
Noncontrolling interest                
Net earnings attributable to National Commerce Corporation                 15,417 6,977 4,360
Total assets 1,903,602       1,718,807       1,903,602 1,718,807 1,099,191
Operating Segments [Member] | Mortgage Division [Member]                      
Interest income [1]                 489 385 410
Interest expense [1]                 200 126 123
Net interest income [1]                 289 259 287
Provision for loan and lease losses [1]                
Noninterest income [1]                 8,039 6,070 4,199
Noninterest expense [1]                 6,604 5,278 3,681
Earnings before income taxes [1]                 1,724 1,051 805
Income tax expense [1]                 655 399 306
Noncontrolling interest [1]                
Net earnings attributable to National Commerce Corporation [1]                 1,069 652 499
Total assets [1] 15,373       15,020       15,373 15,020 9,329
Operating Segments [Member] | Receivables Factoring [Member]                      
Interest income                 11,762 12,400 4,345
Interest expense                 1,944 2,012 731
Net interest income                 9,818 10,388 3,614
Provision for loan and lease losses                 923 (45) 804
Noninterest income                 69 49 22
Noninterest expense                 5,195 5,226 1,724
Earnings before income taxes                 3,769 5,256 1,108
Income tax expense                 838 1,211 226
Noncontrolling interest                 (1,564) (2,069) (512)
Net earnings attributable to National Commerce Corporation                 1,367 1,976 370
Total assets 105,812       90,464       105,812 90,464 105,330
Intersegment Eliminations [Member]                      
Interest income [2]                 (1,944) (2,012) (557)
Interest expense [2]                 (1,944) (2,012) (731)
Net interest income [2]                 174
Provision for loan and lease losses [2]                
Noninterest income [2]                
Noninterest expense [2]                
Earnings before income taxes [2]                 174
Income tax expense [2]                
Noncontrolling interest [2]                
Net earnings attributable to National Commerce Corporation [2]                 174
Total assets [2] $ (74,003)       $ (60,922)       $ (74,003) $ (60,922) $ (75,424)
[1] Noninterest income for the mortgage division segment includes intercompany income allocation.
[2] Entry to remove intercompany interest allocated to the receivables factoring segment. For segment reporting purposes, we allocate funding costs to the receivables factoring segment at the federal funds rate plus 2.50%.