Investments (Summary of Gross Unrealized Losses for Investments that have been Continuously in Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Fair Value 12 months or less	$ 166,678	$ 291,131
Unrealized Losses 12 months or less	(3,477)	(5,269)
Fair Value Longer than 12 months	27,845	28,890
Unrealized Losses Longer than 12 months	(6,859)	(5,604)
Total Fair Value	194,523	320,021
Total Unrealized Losses	(10,336)	(10,873)
Equity Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	2,796	6,584
Unrealized Losses 12 months or less	(474)	(838)
Fair Value Longer than 12 months	1,689
Unrealized Losses Longer than 12 months	(656)
Total Fair Value	4,485	6,584
Total Unrealized Losses	(1,130)	(838)
Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	163,882	284,547
Unrealized Losses 12 months or less	(3,003)	(4,431)
Fair Value Longer than 12 months	26,156	28,890
Unrealized Losses Longer than 12 months	(6,203)	(5,604)
Total Fair Value	190,038	313,437
Total Unrealized Losses	(9,206)	(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	72,123	96,475
Unrealized Losses 12 months or less	(1,472)	(1,822)
Total Fair Value	72,123	96,475
Total Unrealized Losses	(1,472)	(1,822)
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	45,414	65,868
Unrealized Losses 12 months or less	(691)	(1,758)
Fair Value Longer than 12 months	5,314	3,532
Unrealized Losses Longer than 12 months	(96)	(124)
Total Fair Value	50,728	69,400
Total Unrealized Losses	(787)	(1,882)
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	16,565	44,525
Unrealized Losses 12 months or less	(279)	(488)
Fair Value Longer than 12 months	20,798	25,310
Unrealized Losses Longer than 12 months	(6,105)	(5,478)
Total Fair Value	37,363	69,835
Total Unrealized Losses	(6,384)	(5,966)
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	29,780	36,251
Unrealized Losses 12 months or less	(561)	(302)
Fair Value Longer than 12 months	44	48
Unrealized Losses Longer than 12 months	(2)	(2)
Total Fair Value	29,824	36,299
Total Unrealized Losses	$ (563)	$ (304)