Investments (Fixed Maturities and Equity Securities Excluding Investments Classified as Trading) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 4,110,133		$ 4,838,695	[1]
Available-for-sale equity securities amortized cost basis	18		2,510	[1]
Fair Value, Fixed maturities, available for sale	4,527,910		5,273,767	[1]
Equity securities, available for sale	22		3,071	[1]
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	35,363		85,196	[1]
Fair Value, Fixed maturities, available for sale	35,764		86,035	[1]
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	94,734		85,822	[1]
Fair Value, Fixed maturities, available for sale	102,915		94,158	[1]
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	45,855		66,449	[1]
Fair Value, Fixed maturities, available for sale	56,325		77,231	[1]
Corporate Debt Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	3,034,106		3,585,776	[1]
Fair Value, Fixed maturities, available for sale	3,377,235		3,951,209	[1]
Asset-backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	177,191	[2]	172,390	[1],[2]
Fair Value, Fixed maturities, available for sale	184,985	[2]	177,384	[1],[2]
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	399,534		463,576	[1]
Fair Value, Fixed maturities, available for sale	429,529		491,757	[1]
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	323,350	[3]	379,486	[1],[3]
Fair Value, Fixed maturities, available for sale	341,157	[3]	395,993	[1],[3]
Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	420,371		444,275	[1]
Gross Unrealized Losses	2,594		9,203	[1]
Other-than-temporary impairments in AOCI	3,754	[4]	4,197	[1],[5]
Fixed Maturities [Member] | US Treasury And Government [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	401		839	[1]
Gross Unrealized Losses	0		0	[1]
Other-than-temporary impairments in AOCI	0	[4]	0	[1],[5]
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]
Gross Unrealized Gains	8,452		8,336	[1]
Gross Unrealized Losses	271		0	[1]
Other-than-temporary impairments in AOCI	0	[4]	0	[1],[5]
Fixed Maturities [Member] | Foreign Government Debt Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	10,470		10,782	[1]
Gross Unrealized Losses	0		0	[1]
Other-than-temporary impairments in AOCI	0	[4]	0	[1],[5]
Fixed Maturities [Member] | Corporate Debt Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	344,149		369,769	[1]
Gross Unrealized Losses	1,020		4,336	[1]
Other-than-temporary impairments in AOCI	0	[4]	236	[1],[5]
Fixed Maturities [Member] | Asset-backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	9,054	[2]	9,798	[1],[2]
Gross Unrealized Losses	1,260	[2]	4,804	[1],[2]
Other-than-temporary impairments in AOCI	3,704	[2],[4]	3,906	[1],[2],[5]
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	30,038		28,189	[1]
Gross Unrealized Losses	43		8	[1]
Other-than-temporary impairments in AOCI	0	[4]	0	[1],[5]
Fixed Maturities [Member] | Residential Mortgage Backed Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	17,807	[3]	16,562	[1],[3]
Gross Unrealized Losses	0	[3]	55	[1],[3]
Other-than-temporary impairments in AOCI	50	[3],[4]	55	[1],[3],[5]
Equity Securities Available For Sale [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Gross Unrealized Gains	4		561	[1]
Gross Unrealized Losses	0		0	[1]
Other-than-temporary impairments in AOCI		[4]		[1],[5]

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

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

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

[4] Represents the amount of other-than-temporary impairment losses in “AOCI,” which were not included in earnings. Amount excludes $4.4 million of net unrealized gains on impaired securities relating to changes in the value of such securities subsequent to the impairment measurement date.

[5] 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.