Investments (Summary of Gross Unrealized Losses for Investments that have been Continuously in Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Fair Value 12 months or less	$ 128,643	$ 158,413
Unrealized Losses 12 months or less	(2,774)	(2,225)
Fair Value Longer than 12 months	15,194	27,548
Unrealized Losses Longer than 12 months	(1,977)	(1,752)
Total Fair Value	143,837	185,961
Total Unrealized Losses	(4,751)	(3,977)
Equity Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	4,030	129
Unrealized Losses 12 months or less	(300)	(2)
Total Fair Value	4,030	129
Total Unrealized Losses	(300)	(2)
Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	124,613	158,284
Unrealized Losses 12 months or less	(2,474)	(2,223)
Fair Value Longer than 12 months	15,194	27,548
Unrealized Losses Longer than 12 months	(1,977)	(1,752)
Total Fair Value	139,807	185,832
Total Unrealized Losses	(4,451)	(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	17,069	7,552
Unrealized Losses 12 months or less	(59)	(85)
Total Fair Value	17,069	7,552
Total Unrealized Losses	(59)	(85)
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	35,468	64,712
Unrealized Losses 12 months or less	(373)	(824)
Fair Value Longer than 12 months	11,074	8,898
Unrealized Losses Longer than 12 months	(1,695)	(1,091)
Total Fair Value	46,542	73,610
Total Unrealized Losses	(2,068)	(1,915)
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	54,473	50,546
Unrealized Losses 12 months or less	(1,957)	(945)
Fair Value Longer than 12 months	4,113	15,684
Unrealized Losses Longer than 12 months	(282)	(656)
Total Fair Value	58,586	66,230
Total Unrealized Losses	(2,239)	(1,601)
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	17,603	20,469
Unrealized Losses 12 months or less	(85)	(365)
Fair Value Longer than 12 months	7	2,966
Unrealized Losses Longer than 12 months		(5)
Total Fair Value	17,610	23,435
Total Unrealized Losses	$ (85)	$ (370)