Investments (Fixed Maturities and Equity Securities Excluding Investments Classified as Trading) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 3,621,722		$ 3,827,496
Available-for-sale equity securities amortized cost basis	18		18
Fair Value, Fixed maturities, available for sale	3,948,208		4,203,450
Equity securities, available for sale	22		22
Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	3,621,722		3,827,496
Gross Unrealized Gains	328,407		377,873
Gross Unrealized Losses	1,921		1,919
Fair Value, Fixed maturities, available for sale	3,948,208		4,203,450
Other-than-temporary impairments in AOCI	1,398	[1]	3,562	[2]
Fixed Maturities [Member] | US Treasury And Government [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	4,556		4,568
Gross Unrealized Gains	98		118
Gross Unrealized Losses	0		0
Fair Value, Fixed maturities, available for sale	4,654		4,686
Other-than-temporary impairments in AOCI	0	[1]	0	[2]
Fixed Maturities [Member] | Obligations of U.S. states and their political subdivisions [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	95,765		95,107
Gross Unrealized Gains	6,993		7,359
Gross Unrealized Losses	315		350
Fair Value, Fixed maturities, available for sale	102,443		102,116
Other-than-temporary impairments in AOCI	0	[1]	0	[2]
Fixed Maturities [Member] | Foreign Government Debt Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	30,510		45,733
Gross Unrealized Gains	9,076		9,796
Gross Unrealized Losses	0		0
Fair Value, Fixed maturities, available for sale	39,586		55,529
Other-than-temporary impairments in AOCI	0	[1]	0	[2]
Fixed Maturities [Member] | Public Utilities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	243,597		253,566
Gross Unrealized Gains	26,724		29,554
Gross Unrealized Losses	543		569
Fair Value, Fixed maturities, available for sale	269,778		282,551
Other-than-temporary impairments in AOCI	0	[1]	0
Fixed Maturities [Member] | Corporate Debt Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	2,470,504		2,622,982
Gross Unrealized Gains	244,000		283,117
Gross Unrealized Losses	734		658
Fair Value, Fixed maturities, available for sale	2,713,770		2,905,441
Other-than-temporary impairments in AOCI	0	[1]	0	[2]
Fixed Maturities [Member] | Asset-backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	173,529	[3]	179,037	[3]
Gross Unrealized Gains	9,618	[3]	8,772	[3]
Gross Unrealized Losses	14	[3]	332	[3]
Fair Value, Fixed maturities, available for sale	183,133	[3]	187,477	[3]
Other-than-temporary impairments in AOCI	1,352	[1],[3]	3,514	[2],[3]
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	379,751		369,187
Gross Unrealized Gains	21,141		25,725
Gross Unrealized Losses	315		10
Fair Value, Fixed maturities, available for sale	400,577		394,902
Other-than-temporary impairments in AOCI	0	[1]	0	[2]
Fixed Maturities [Member] | Residential Mortgage Backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	223,510	[4]	254,751	[4]
Gross Unrealized Gains	10,757	[4]	12,735	[4]
Gross Unrealized Losses	0	[4]	0	[4]
Fair Value, Fixed maturities, available for sale	234,267	[4]	267,486	[4]
Other-than-temporary impairments in AOCI	46	[1],[4]	48	[2],[4]
Fixed Maturities [Member] | RedeemablePreferred
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	0		2,565
Gross Unrealized Gains	0		697
Gross Unrealized Losses	0		0
Fair Value, Fixed maturities, available for sale	0		3,262
Other-than-temporary impairments in AOCI	0	[1]	0	[2]
Equity Securities Available For Sale [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Available-for-sale equity securities amortized cost basis	18		18
Gross Unrealized Gains	4		4
Gross Unrealized Losses	0		0
Equity securities, available for sale	22		22
Equity Securities Available For Sale [Member] | Industrial, Miscellaneous, and All Others [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Available-for-sale equity securities amortized cost basis	0		18
Gross Unrealized Gains	0		4
Gross Unrealized Losses	0		0
Equity securities, available for sale	0		22
Equity Securities Available For Sale [Member] | Mutual Fund [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Available-for-sale equity securities amortized cost basis	18
Gross Unrealized Gains	4
Gross Unrealized Losses	0
Equity securities, available for sale	$ 22

[1] Represents the amount of other-than-temporary impairment losses in “AOCI,” which were not included in earnings. Amount excludes $1.8 million of net unrealized gains on impaired securities relating to changes in the value of such securities subsequent to the impairment measurement date.

[2] Represents the amount of other-than-temporary impairment losses in AOCI, which were not included in earnings. Amount excludes $4.1 million of net unrealized gains on impaired securities relating to changes in the value of such securities subsequent to the impairment measurement date.

[3] Includes credit-tranched securities collateralized by sub-prime mortgages, credit cards, education loans, and other asset types.

[4] Includes publicly-traded agency pass-through securities and collateralized mortgage obligations.