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, 2014	Dec. 31, 2013
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	$ 322,351	$ 643,930	[1]
Less than 12 months Gross Unrealized Losses	5,969	20,275	[1]
Twelve months or more Fair Value	58,991	12,047	[1]
Twelve months or more Gross Unrealized Losses	1,152	1,621	[1]
Total Fair Value	381,342	655,977	[1]
Total Gross Unrealized Losses	7,121	21,896	[1]
US Treasury And Government [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	2,676	3,347	[1]
Less than 12 months Gross Unrealized Losses	10	34	[1]
Twelve months or more Fair Value	0	0	[1]
Twelve months or more Gross Unrealized Losses	0	0	[1]
Total Fair Value	2,676	3,347	[1]
Total Gross Unrealized Losses	10	34	[1]
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	[1]
Less than 12 months Gross Unrealized Losses	0	588	[1]
Twelve months or more Fair Value	7,305	6,402	[1]
Twelve months or more Gross Unrealized Losses	20	982	[1]
Total Fair Value	7,305	11,822	[1]
Total Gross Unrealized Losses	20	1,570	[1]
Foreign Government Debt Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	4,632
Less than 12 months Gross Unrealized Losses	4
Twelve months or more Fair Value	0
Twelve months or more Gross Unrealized Losses	0
Total Fair Value	4,632
Total Gross Unrealized Losses	4
Corporate Debt Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	260,414	291,994	[1]
Less than 12 months Gross Unrealized Losses	4,462	8,782	[1]
Twelve months or more Fair Value	9,403	2,704	[1]
Twelve months or more Gross Unrealized Losses	429	370	[1]
Total Fair Value	269,817	294,698	[1]
Total Gross Unrealized Losses	4,891	9,152	[1]
Asset-backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	31,756	97,575	[1]
Less than 12 months Gross Unrealized Losses	58	1,509	[1]
Twelve months or more Fair Value	32,732	0	[1]
Twelve months or more Gross Unrealized Losses	333	0	[1]
Total Fair Value	64,488	97,575	[1]
Total Gross Unrealized Losses	391	1,509	[1]
Commercial Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	4,309	86,132	[1]
Less than 12 months Gross Unrealized Losses	108	5,249	[1]
Twelve months or more Fair Value	7,377	2,941	[1]
Twelve months or more Gross Unrealized Losses	98	269	[1]
Total Fair Value	11,686	89,073	[1]
Total Gross Unrealized Losses	206	5,518	[1]
Residential Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	342	100,150	[1]
Less than 12 months Gross Unrealized Losses	6	972	[1]
Twelve months or more Fair Value	0	0	[1]
Twelve months or more Gross Unrealized Losses	0	0	[1]
Total Fair Value	342	100,150	[1]
Total Gross Unrealized Losses	6	972	[1]
PublicUtilityBondsMember
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	18,222	59,312	[1]
Less than 12 months Gross Unrealized Losses	1,321	3,141	[1]
Twelve months or more Fair Value	2,174	0	[1]
Twelve months or more Gross Unrealized Losses	272	0	[1]
Total Fair Value	20,396	59,312	[1]
Total Gross Unrealized Losses	$ 1,593	$ 3,141	[1]

[1] Prior period’s amounts are presented on a basis consistent with the current period presentation.