Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	$ 111,684	$ 59,481
Less than 12 months Gross Unrealized Losses	1,706	1,299
Twelve months or more Fair Value	12,368	17,861
Twelve months or more Gross Unrealized Losses	215	620
Total Fair Value	124,052	77,342
Total Gross Unrealized Losses	1,921	1,919
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	7,111	7,090
Less than 12 months Gross Unrealized Losses	315	350
Twelve months or more Fair Value	0	0
Twelve months or more Gross Unrealized Losses	0	0
Total Fair Value	7,111	7,090
Total Gross Unrealized Losses	315	350
Corporate Debt Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	76,285	35,248
Less than 12 months Gross Unrealized Losses	1,077	897
Twelve months or more Fair Value	11,881	14,867
Twelve months or more Gross Unrealized Losses	200	330
Total Fair Value	88,166	50,115
Total Gross Unrealized Losses	1,277	1,227
Asset-backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	387	13,817
Less than 12 months Gross Unrealized Losses	0	42
Twelve months or more Fair Value	80	2,994
Twelve months or more Gross Unrealized Losses	14	290
Total Fair Value	467	16,811
Total Gross Unrealized Losses	14	332
Commercial Mortgage Backed Securities [Member]
Duration Of Unrealized Losses On Fixed Maturities Investments [Line Items]
Less than twelve months Fair Value	27,901	3,326
Less than 12 months Gross Unrealized Losses	314	10
Twelve months or more Fair Value	407	0
Twelve months or more Gross Unrealized Losses	1	0
Total Fair Value	28,308	3,326
Total Gross Unrealized Losses	$ 315	$ 10