Fair Value Disclosures (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Assets
Fixed maturity securities	$ 16,794,057	$ 16,200,950
Mortgage loans on real estate	1,040,733	991,731
Policy loans	1,260,070	1,260,400
Funds withheld at interest	5,472,532	5,410,424
Short-term investments	75,425	88,566
Other invested assets	867,507	1,012,541
Cash and cash equivalents	873,933	962,870	467,672	463,661
Accrued Investment Income	173,629	144,334
Reinsurance ceded receivables	597,508	626,194
Liabilities
Interest-sensitive contract liabilities	8,252,995	8,394,468
Collateral finance facility	652,029	652,032
Fair Value Inputs Level 1 Member
Assets
Fixed maturity securities	434,960	612,945
Fair Value Inputs Level 2 Member
Assets
Fixed maturity securities	15,056,712	14,212,340
Fair Value Inputs Level 3 Member
Assets
Fixed maturity securities	1,302,385	1,375,665
Carrying Value [Member]
Assets
Mortgage loans on real estate	1,040,733	991,731
Policy loans	1,260,070	1,260,400
Funds withheld at interest	5,472,532	5,410,424
Short-term investments	56,230	41,895
Other invested assets	494,561	500,681
Cash and cash equivalents	524,476	458,348
Accrued Investment Income	173,629	144,334
Liabilities
Interest-sensitive contract liabilities	6,213,484	6,203,001
Long And Short Term Debt	1,414,829	1,414,688
Collateral finance facility	652,029	652,032
Estimated Fair Value [Member]
Assets
Mortgage loans on real estate	1,140,083	1,081,924
Policy loans	1,260,070	1,260,400
Funds withheld at interest	6,186,149	6,041,984
Short-term investments	56,230	41,895
Other invested assets	498,040	503,293
Cash and cash equivalents	524,476	458,348
Accrued Investment Income	173,629	144,334
Liabilities
Interest-sensitive contract liabilities	6,364,422	6,307,779
Long And Short Term Debt	1,484,949	1,462,329
Collateral finance facility	423,475	390,900
Estimated Fair Value [Member] | Fair Value Inputs Level 1 Member
Assets
Mortgage loans on real estate	0
Policy loans	0
Funds withheld at interest	0
Short-term investments	56,230
Other invested assets	0
Cash and cash equivalents	524,476
Accrued Investment Income	0
Liabilities
Interest-sensitive contract liabilities	0
Long And Short Term Debt	0
Collateral finance facility	0
Estimated Fair Value [Member] | Fair Value Inputs Level 2 Member
Assets
Mortgage loans on real estate	0
Policy loans	1,260,070
Funds withheld at interest	0
Short-term investments	0
Other invested assets	18,799
Cash and cash equivalents	0
Accrued Investment Income	173,629
Liabilities
Interest-sensitive contract liabilities	0
Long And Short Term Debt	0
Collateral finance facility	0
Estimated Fair Value [Member] | Fair Value Inputs Level 3 Member
Assets
Mortgage loans on real estate	1,140,083
Policy loans	0
Funds withheld at interest	6,186,149
Short-term investments	0
Other invested assets	479,241
Cash and cash equivalents	0
Accrued Investment Income	0
Liabilities
Interest-sensitive contract liabilities	6,364,422
Long And Short Term Debt	1,484,949
Collateral finance facility	$ 423,475