Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	$ 112,577	$ 643,930
Less than 12 months Gross Unrealized Losses	1,150	20,275
Twelve months or more Fair Value	79,848	12,047
Twelve months or more Gross Unrealized Losses	1,737	1,621
Total Fair Value	192,425	655,977
Total Gross Unrealized Losses	2,887	21,896
US Treasury And Government [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	2,692	3,347
Less than 12 months Gross Unrealized Losses	10	34
Twelve months or more Fair Value	0	0
Twelve months or more Gross Unrealized Losses	0	0
Total Fair Value	2,692	3,347
Total Gross Unrealized Losses	10	34
Obligations of U.S. states and their political subdivisions [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	0	5,420
Less than 12 months Gross Unrealized Losses	0	588
Twelve months or more Fair Value	6,995	6,402
Twelve months or more Gross Unrealized Losses	360	982
Total Fair Value	6,995	11,822
Total Gross Unrealized Losses	360	1,570
Corporate Debt Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	94,815	351,306
Less than 12 months Gross Unrealized Losses	1,001	11,923
Twelve months or more Fair Value	47,798	2,704
Twelve months or more Gross Unrealized Losses	1,041	370
Total Fair Value	142,613	354,010
Total Gross Unrealized Losses	2,042	12,293
Asset-backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	15,070	97,575
Less than 12 months Gross Unrealized Losses	139	1,509
Twelve months or more Fair Value	17,832	0
Twelve months or more Gross Unrealized Losses	81	0
Total Fair Value	32,902	97,575
Total Gross Unrealized Losses	220	1,509
Commercial Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	0	86,132
Less than 12 months Gross Unrealized Losses	0	5,249
Twelve months or more Fair Value	7,223	2,941
Twelve months or more Gross Unrealized Losses	255	269
Total Fair Value	7,223	89,073
Total Gross Unrealized Losses	255	5,518
Residential Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	0	100,150
Less than 12 months Gross Unrealized Losses	0	972
Twelve months or more Fair Value	0	0
Twelve months or more Gross Unrealized Losses	0	0
Total Fair Value	0	100,150
Total Gross Unrealized Losses	$ 0	$ 972