Investments (Summary of Gross Unrealized Losses for Investments that have been Continuously in Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Fair Value 12 months or less	$ 136,290	$ 291,131
Unrealized Losses 12 months or less	(1,790)	(5,269)
Fair Value Longer than 12 months	23,906	28,890
Unrealized Losses Longer than 12 months	(3,385)	(5,604)
Total Fair Value	160,196	320,021
Total Unrealized Losses	(5,175)	(10,873)
Equity Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	4,341	6,584
Unrealized Losses 12 months or less	(435)	(838)
Fair Value Longer than 12 months	1,689
Unrealized Losses Longer than 12 months	(681)
Total Fair Value	6,030	6,584
Total Unrealized Losses	(1,116)	(838)
Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	131,949	284,547
Unrealized Losses 12 months or less	(1,355)	(4,431)
Fair Value Longer than 12 months	22,217	28,890
Unrealized Losses Longer than 12 months	(2,704)	(5,604)
Total Fair Value	154,166	313,437
Total Unrealized Losses	(4,059)	(10,035)
Us Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less		41,428
Unrealized Losses 12 months or less		(61)
Total Fair Value		41,428
Total Unrealized Losses		(61)
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	44,961	96,475
Unrealized Losses 12 months or less	(465)	(1,822)
Total Fair Value	44,961	96,475
Total Unrealized Losses	(465)	(1,822)
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	37,748	65,868
Unrealized Losses 12 months or less	(430)	(1,758)
Fair Value Longer than 12 months	4,316	3,532
Unrealized Losses Longer than 12 months	(63)	(124)
Total Fair Value	42,064	69,400
Total Unrealized Losses	(493)	(1,882)
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	14,803	44,525
Unrealized Losses 12 months or less	(325)	(488)
Fair Value Longer than 12 months	17,860	25,310
Unrealized Losses Longer than 12 months	(2,639)	(5,478)
Total Fair Value	32,663	69,835
Total Unrealized Losses	(2,964)	(5,966)
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	34,437	36,251
Unrealized Losses 12 months or less	(135)	(302)
Fair Value Longer than 12 months	41	48
Unrealized Losses Longer than 12 months	(2)	(2)
Total Fair Value	34,478	36,299
Total Unrealized Losses	$ (137)	$ (304)