Investments (Fixed Maturities and Equity Securities Excluding Investments Classified as Trading) (Details) (USD $)	Jun. 30, 2013		Dec. 31, 2012
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 3,491,116,000		$ 3,827,496,000
Available-for-sale equity securities amortized cost basis	18,000		18,000
Fair Value, Fixed maturities, available for sale	3,704,512,000		4,203,450,000
Equity securities, available for sale	20,000		22,000
Net unrealized gains on impaired securities relating to changes in value of securities subsequent to the impairment measurement date	1,700,000		4,100,000
Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Fixed maturities, available-for-sale, amortized cost	3,491,116,000		3,827,496,000
Gross Unrealized Gains	239,954,000		377,873,000
Gross Unrealized Losses	26,558,000		1,919,000
Fair Value, Fixed maturities, available for sale	3,704,512,000		4,203,450,000
Other-than-temporary impairments in AOCI	1,396,000	[1]	3,562,000	[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	4,658,000		4,568,000
Gross Unrealized Gains	77,000		118,000
Gross Unrealized Losses	0		0
Fair Value, Fixed maturities, available for sale	4,735,000		4,686,000
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	96,150,000		95,107,000
Gross Unrealized Gains	4,675,000		7,359,000
Gross Unrealized Losses	1,253,000		350,000
Fair Value, Fixed maturities, available for sale	99,572,000		102,116,000
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	30,457,000		45,733,000
Gross Unrealized Gains	7,232,000		9,796,000
Gross Unrealized Losses	0		0
Fair Value, Fixed maturities, available for sale	37,689,000		55,529,000
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	248,897,000		253,566,000
Gross Unrealized Gains	16,544,000		29,554,000
Gross Unrealized Losses	3,725,000		569,000
Fair Value, Fixed maturities, available for sale	261,716,000		282,551,000
Other-than-temporary impairments in AOCI	0	[1]	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	2,357,358,000		2,622,982,000
Gross Unrealized Gains	181,390,000		283,117,000
Gross Unrealized Losses	15,604,000		658,000
Fair Value, Fixed maturities, available for sale	2,523,144,000		2,905,441,000
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	182,703,000	[3]	179,037,000	[3]
Gross Unrealized Gains	8,286,000	[3]	8,772,000	[3]
Gross Unrealized Losses	38,000	[3]	332,000	[3]
Fair Value, Fixed maturities, available for sale	190,951,000	[3]	187,477,000	[3]
Other-than-temporary impairments in AOCI	1,352,000	[1],[3]	3,514,000	[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	371,503,000		369,187,000
Gross Unrealized Gains	15,374,000		25,725,000
Gross Unrealized Losses	5,302,000		10,000
Fair Value, Fixed maturities, available for sale	381,575,000		394,902,000
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	199,390,000	[4]	254,751,000	[4]
Gross Unrealized Gains	6,376,000	[4]	12,735,000	[4]
Gross Unrealized Losses	636,000	[4]	0	[4]
Fair Value, Fixed maturities, available for sale	205,130,000	[4]	267,486,000	[4]
Other-than-temporary impairments in AOCI	44,000	[1],[4]	48,000	[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		2,565,000
Gross Unrealized Gains	0		697,000
Gross Unrealized Losses	0		0
Fair Value, Fixed maturities, available for sale	0		3,262,000
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	18,000		18,000
Gross Unrealized Gains	2,000		4,000
Gross Unrealized Losses	0		0
Equity securities, available for sale	20,000		22,000
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
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Equity securities, available for sale	0
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	18,000		18,000	[5]
Gross Unrealized Gains	2,000		4,000	[5]
Gross Unrealized Losses	0		0	[5]
Equity securities, available for sale	$ 20,000		$ 22,000	[5]

[1] Represents the amount of other-than-temporary impairment losses in “AOCI,” which were not included in earnings. Amount excludes $1.7 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.

[5] Prior period has been reclassified to conform to the current period presentation.