Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities) (Details) - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
$ 563,580
|
$ 476,130
|
| Investments, Gross Unrealized Gains |
26,122
|
35,076
|
| Investments, Gross Unrealized Losses |
(10,873)
|
(3,977)
|
| Total investments |
578,829
|
507,229
|
| Equity Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
24,951
|
25,360
|
| Investments, Gross Unrealized Gains |
23,391
|
31,086
|
| Investments, Gross Unrealized Losses |
(838)
|
(2)
|
| Total investments |
47,504
|
56,444
|
| Debt Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
538,629
|
450,770
|
| Investments, Gross Unrealized Gains |
2,731
|
3,990
|
| Investments, Gross Unrealized Losses |
(10,035)
|
(3,975)
|
| Total investments |
531,325
|
450,785
|
| U.S. Treasury securities and obligations of U.S. Government [Member] | Debt Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
76,323
|
93,280
|
| Investments, Gross Unrealized Gains |
7
|
29
|
| Investments, Gross Unrealized Losses |
(61)
|
(4)
|
| Total investments |
76,269
|
93,305
|
| Corporate Bonds [Member] | Debt Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
122,894
|
28,643
|
| Investments, Gross Unrealized Gains |
637
|
884
|
| Investments, Gross Unrealized Losses |
(1,822)
|
(85)
|
| Total investments |
121,709
|
29,442
|
| Collateralized Corporate Bank Loans [Member] | Debt Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
83,434
|
115,358
|
| Investments, Gross Unrealized Gains |
44
|
206
|
| Investments, Gross Unrealized Losses |
(1,882)
|
(1,915)
|
| Total investments |
81,596
|
113,649
|
| Municipal Bonds [Member] | Debt Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
196,446
|
161,546
|
| Investments, Gross Unrealized Gains |
1,888
|
2,384
|
| Investments, Gross Unrealized Losses |
(5,966)
|
(1,601)
|
| Total investments |
192,368
|
162,329
|
| Collateralized Mortgage Backed Securities [Member] | Debt Securities [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Investments, Amortized Cost |
59,532
|
51,943
|
| Investments, Gross Unrealized Gains |
155
|
487
|
| Investments, Gross Unrealized Losses |
(304)
|
(370)
|
| Total investments |
$ 59,383
|
$ 52,060
|