Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012	Dec. 31, 2011
Assets
Mortgage loans on real estate (net of valuation allowances)	$ 2,488,582		$ 2,300,587
Policy loans	1,244,878		1,278,175
Funds withheld at interest	5,739,872		5,594,182
Cash and cash equivalents	1,423,235		1,259,892		1,603,730	962,870
Short-term investments	44,192		288,082
Other invested assets	1,116,391		1,159,543
Accrued investment income	262,330		201,344
Liabilities
Interest-sensitive contract liabilities	12,868,425		13,353,502
Collateral finance facility	484,712		652,010
Carrying Value [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)	2,488,582		2,300,587
Policy loans	1,244,878		1,278,175
Funds withheld at interest	5,917,002	[1]	5,837,359	[1]
Cash and cash equivalents	751,236	[2]	684,028	[2]
Short-term investments	24,756	[2]	48,951	[2]
Other invested assets	652,759	[2]	596,336	[2]
Accrued investment income	262,330		201,344
Liabilities
Interest-sensitive contract liabilities	11,104,386	[1]	11,566,962	[1]
Long And Short Term Debt	2,214,170		1,815,253
Collateral finance facility	484,712		652,010
Estimate of Fair Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)	2,515,250		2,426,688
Policy loans	1,244,878		1,278,175
Funds withheld at interest	6,144,891	[1]	6,362,324	[1]
Cash and cash equivalents	751,236	[2]	684,028	[2]
Short-term investments	24,756	[2]	48,951	[2]
Other invested assets	694,909	[2]	626,358	[2]
Accrued investment income	262,330		201,344
Liabilities
Interest-sensitive contract liabilities	10,923,043	[1]	11,926,339	[1]
Long And Short Term Debt	2,348,049		2,014,062
Collateral finance facility	365,307		456,050
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 1 Member
Assets
Mortgage loans on real estate (net of valuation allowances)	0		0
Policy loans	0		0
Funds withheld at interest	0	[1]	0	[1]
Cash and cash equivalents	751,236	[2]	684,028	[2]
Short-term investments	24,756	[2]	48,951	[2]
Other invested assets	4,956	[2]	0	[2]
Accrued investment income	0		0
Liabilities
Interest-sensitive contract liabilities	0	[1]	0	[1]
Long And Short Term Debt	0		0
Collateral finance facility	0		0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 2 Member
Assets
Mortgage loans on real estate (net of valuation allowances)	0		0
Policy loans	1,244,878		1,278,175
Funds withheld at interest	0	[1]	0	[1]
Cash and cash equivalents	0	[2]	0	[2]
Short-term investments	0	[2]	0	[2]
Other invested assets	31,436	[2]	32,250	[2]
Accrued investment income	262,330		201,344
Liabilities
Interest-sensitive contract liabilities	0	[1]	0	[1]
Long And Short Term Debt	0		0
Collateral finance facility	0		0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 3 Member
Assets
Mortgage loans on real estate (net of valuation allowances)	2,515,250		2,426,688
Policy loans	0		0
Funds withheld at interest	6,144,891	[1]	6,362,324	[1]
Cash and cash equivalents	0	[2]	0	[2]
Short-term investments	0	[2]	0	[2]
Other invested assets	658,517	[2]	594,108	[2]
Accrued investment income	0		0
Liabilities
Interest-sensitive contract liabilities	10,923,043	[1]	11,926,339	[1]
Long And Short Term Debt	2,348,049		2,014,062
Collateral finance facility	$ 365,307		$ 456,050

[1] Carrying values presented herein differ from those presented in the condensed consolidated balance sheets because certain items within the respective financial statement caption are embedded derivatives and are measured at fair value on a recurring basis.

[2] Carrying values presented herein differ from those presented in the condensed consolidated balance sheets because certain items within the respective financial statement caption are measured at fair value on a recurring basis.