Investments (Fixed Maturities and Equity Securities Excluding Investments Classified as Trading) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 3,827,496
Fair Value, Fixed maturities, available for sale	4,203,450		5,273,767
Equity securities, available for sale	22		3,071
Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	3,827,496		4,838,695	[1]
Gross Unrealized Gains	377,873		444,275	[1]
Gross Unrealized Losses	1,919		9,203	[1]
Fair Value, Fixed maturities, available for sale	4,203,450		5,273,767	[1]
Other-than-temporary impairments in AOCI	3,562	[2]	4,197	[1],[3]
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	4,568		85,196	[1]
Gross Unrealized Gains	118		839	[1]
Gross Unrealized Losses	0		0	[1]
Fair Value, Fixed maturities, available for sale	4,686		86,035	[1]
Other-than-temporary impairments in AOCI	0	[2]	0	[1],[3]
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	95,107		85,822	[1]
Gross Unrealized Gains	7,359		8,336	[1]
Gross Unrealized Losses	350		0	[1]
Fair Value, Fixed maturities, available for sale	102,116		94,158	[1]
Other-than-temporary impairments in AOCI	0	[2]	0	[1],[3]
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	45,733		66,449	[1]
Gross Unrealized Gains	9,796		10,782	[1]
Gross Unrealized Losses	0		0	[1]
Fair Value, Fixed maturities, available for sale	55,529		77,231	[1]
Other-than-temporary impairments in AOCI	0	[2]	0	[1],[3]
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	253,566
Gross Unrealized Gains	29,554
Gross Unrealized Losses	569
Fair Value, Fixed maturities, available for sale	282,551
Other-than-temporary impairments in AOCI	0	[2]
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	2,622,982		3,580,396	[1]
Gross Unrealized Gains	283,117		368,444	[1]
Gross Unrealized Losses	658		4,336	[1]
Fair Value, Fixed maturities, available for sale	2,905,441		3,944,504	[1]
Other-than-temporary impairments in AOCI	0	[2]	236	[1],[3]
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	179,037	[4]	172,390	[1],[4]
Gross Unrealized Gains	8,772	[4]	9,798	[1],[4]
Gross Unrealized Losses	332	[4]	4,804	[1],[4]
Fair Value, Fixed maturities, available for sale	187,477	[4]	177,384	[1],[4]
Other-than-temporary impairments in AOCI	3,514	[2],[4]	3,906	[1],[3],[4]
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	369,187		463,576	[1]
Gross Unrealized Gains	25,725		28,189	[1]
Gross Unrealized Losses	10		8	[1]
Fair Value, Fixed maturities, available for sale	394,902		491,757	[1]
Other-than-temporary impairments in AOCI	0	[2]	0	[1],[3]
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	254,751	[5]	379,486	[1],[5]
Gross Unrealized Gains	12,735	[5]	16,562	[1],[5]
Gross Unrealized Losses	0	[5]	55	[1],[5]
Fair Value, Fixed maturities, available for sale	267,486	[5]	395,993	[1],[5]
Other-than-temporary impairments in AOCI	48	[2],[5]	55	[1],[3],[5]
Fixed Maturities [Member] | RedeemablePreferred
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	2,565		5,380	[1]
Gross Unrealized Gains	697		1,325	[1]
Gross Unrealized Losses	0		0	[1]
Fair Value, Fixed maturities, available for sale	3,262		6,705	[1]
Other-than-temporary impairments in AOCI	0	[2]	0	[1],[3]
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		2,510	[1]
Gross Unrealized Gains	4		561	[1]
Gross Unrealized Losses	0		0	[1]
Equity securities, available for sale	22		3,071	[6]
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	18		2,510	[1]
Gross Unrealized Gains	4		561	[1]
Gross Unrealized Losses	0		0	[1]
Equity securities, available for sale	$ 22		$ 3,071	[1]

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

[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] Represents the amount of other-than-temporary impairment losses in AOCI, which were not included in earnings. Amount excludes $2.4 million of net unrealized gains on impaired securities relating to changes in the value of such securities subsequent to the impairment measurement date.

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

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

[6] (1) Amounts deferred in “Accumulated other comprehensive income (loss).”