Investments (Summary of Gross Unrealized Losses for Investments that have been Continuously in Unrealized Loss Position) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Fair Value 12 months or less	$ 159,947	$ 158,413
Unrealized Losses 12 months or less	(3,362)	(2,225)
Fair Value Longer than 12 months	26,700	27,548
Unrealized Losses Longer than 12 months	(6,800)	(1,752)
Total Fair Value	186,647	185,961
Total Unrealized Losses	(10,162)	(3,977)
Equity Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	4,611	129
Unrealized Losses 12 months or less	(726)	(2)
Total Fair Value	4,611	129
Total Unrealized Losses	(726)	(2)
Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	155,336	158,284
Unrealized Losses 12 months or less	(2,636)	(2,223)
Fair Value Longer than 12 months	26,700	27,548
Unrealized Losses Longer than 12 months	(6,800)	(1,752)
Total Fair Value	182,036	185,832
Total Unrealized Losses	(9,436)	(3,975)
US Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less		15,005
Unrealized Losses 12 months or less		(4)
Total Fair Value		15,005
Total Unrealized Losses		(4)
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	30,917	7,552
Unrealized Losses 12 months or less	(614)	(85)
Total Fair Value	30,917	7,552
Total Unrealized Losses	(614)	(85)
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	59,675	64,712
Unrealized Losses 12 months or less	(1,387)	(824)
Fair Value Longer than 12 months	4,643	8,898
Unrealized Losses Longer than 12 months	(981)	(1,091)
Total Fair Value	64,318	73,610
Total Unrealized Losses	(2,368)	(1,915)
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	38,894	50,546
Unrealized Losses 12 months or less	(517)	(945)
Fair Value Longer than 12 months	21,985	15,684
Unrealized Losses Longer than 12 months	(5,817)	(656)
Total Fair Value	60,879	66,230
Total Unrealized Losses	(6,334)	(1,601)
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	25,850	20,469
Unrealized Losses 12 months or less	(118)	(365)
Fair Value Longer than 12 months	72	2,966
Unrealized Losses Longer than 12 months	(2)	(5)
Total Fair Value	25,922	23,435
Total Unrealized Losses	$ (120)	$ (370)