Investments (Summary of Gross Unrealized Losses for Investments that have been Continuously in Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Fair Value 12 months or less	$ 161,221	$ 200,483
Unrealized Losses 12 months or less	(1,138)	(2,760)
Fair Value Longer than 12 months	20,956	26,355
Unrealized Losses Longer than 12 months	(2,983)	(2,109)
Total Fair Value	182,177	226,838
Total Unrealized Losses	(4,121)	(4,869)
Equity Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	490	4,109
Unrealized Losses 12 months or less	(4)	(483)
Fair Value Longer than 12 months	1,978	2,037
Unrealized Losses Longer than 12 months	(171)	(307)
Total Fair Value	2,468	6,146
Total Unrealized Losses	(175)	(790)
Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	160,731	196,374
Unrealized Losses 12 months or less	(1,134)	(2,277)
Fair Value Longer than 12 months	18,978	24,318
Unrealized Losses Longer than 12 months	(2,812)	(1,802)
Total Fair Value	179,709	220,692
Total Unrealized Losses	(3,946)	(4,079)
Us Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	7,040	7,037
Unrealized Losses 12 months or less	(14)	(20)
Total Fair Value	7,040	7,037
Total Unrealized Losses	(14)	(20)
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	73,005	86,592
Unrealized Losses 12 months or less	(274)	(575)
Total Fair Value	73,005	86,592
Total Unrealized Losses	(274)	(575)
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	3,209	2,637
Unrealized Losses 12 months or less	(21)	(7)
Fair Value Longer than 12 months	3,837	8,314
Unrealized Losses Longer than 12 months	(132)	(163)
Total Fair Value	7,046	10,951
Total Unrealized Losses	(153)	(170)
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	55,275	70,633
Unrealized Losses 12 months or less	(566)	(1,327)
Fair Value Longer than 12 months	13,113	13,574
Unrealized Losses Longer than 12 months	(2,676)	(1,634)
Total Fair Value	68,388	84,207
Total Unrealized Losses	(3,242)	(2,961)
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Fair Value 12 months or less	22,202	29,475
Unrealized Losses 12 months or less	(259)	(348)
Fair Value Longer than 12 months	2,028	2,430
Unrealized Losses Longer than 12 months	(4)	(5)
Total Fair Value	24,230	31,905
Total Unrealized Losses	$ (263)	$ (353)