Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	$ 643,930	$ 59,481
Less than 12 months Gross Unrealized Losses	20,275	1,299
Twelve months or more Fair Value	12,047	17,861
Twelve months or more Gross Unrealized Losses	1,621	620
Total Fair Value	655,977	77,342
Total Gross Unrealized Losses	21,896	1,919
US Treasury And Government [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	3,347	0
Less than 12 months Gross Unrealized Losses	34	0
Twelve months or more Fair Value	0	0
Twelve months or more Gross Unrealized Losses	0	0
Total Fair Value	3,347	0
Total Gross Unrealized Losses	34	0
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	5,420	7,090
Less than 12 months Gross Unrealized Losses	588	350
Twelve months or more Fair Value	6,402	0
Twelve months or more Gross Unrealized Losses	982	0
Total Fair Value	11,822	7,090
Total Gross Unrealized Losses	1,570	350
Corporate Debt Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	351,306	35,248
Less than 12 months Gross Unrealized Losses	11,923	897
Twelve months or more Fair Value	2,704	14,867
Twelve months or more Gross Unrealized Losses	370	330
Total Fair Value	354,010	50,115
Total Gross Unrealized Losses	12,293	1,227
Asset-backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	97,575	13,817
Less than 12 months Gross Unrealized Losses	1,509	42
Twelve months or more Fair Value	0	2,994
Twelve months or more Gross Unrealized Losses	0	290
Total Fair Value	97,575	16,811
Total Gross Unrealized Losses	1,509	332
Commercial Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	86,132	3,326
Less than 12 months Gross Unrealized Losses	5,249	10
Twelve months or more Fair Value	2,941	0
Twelve months or more Gross Unrealized Losses	269	0
Total Fair Value	89,073	3,326
Total Gross Unrealized Losses	5,518	10
Residential Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	100,150	0
Less than 12 months Gross Unrealized Losses	972	0
Twelve months or more Fair Value	0	0
Twelve months or more Gross Unrealized Losses	0	0
Total Fair Value	100,150	0
Total Gross Unrealized Losses	$ 972	$ 0