Certain Nontraditional Long-Duration Contracts (Summary of the Changes in General Account Liabilities for Guarantees on Variable Contracts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended										12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2012 variableannuity	Dec. 31, 2011 variableannuity	Dec. 31, 2010 variableannuity	Dec. 31, 2009 variableannuity	Dec. 31, 2012 GuaranteedMinimumAccumulationWithdrawalIncomeAndWithdrawalBenefitsMember [Member] variableannuity		Dec. 31, 2011 GuaranteedMinimumAccumulationWithdrawalIncomeAndWithdrawalBenefitsMember [Member] variableannuity		Dec. 31, 2010 GuaranteedMinimumAccumulationWithdrawalIncomeAndWithdrawalBenefitsMember [Member] variableannuity		Dec. 31, 2012 GuaranteedMinimumIncomeBenefitMember variableannuity		Dec. 31, 2011 GuaranteedMinimumIncomeBenefitMember variableannuity		Dec. 31, 2010 GuaranteedMinimumIncomeBenefitMember variableannuity		Dec. 31, 2012 GuaranteedMinimumDeathBenefitMember variableannuity		Dec. 31, 2011 GuaranteedMinimumDeathBenefitMember variableannuity		Dec. 31, 2010 GuaranteedMinimumDeathBenefitMember variableannuity
Net Amount At Risk By Product And Guarantee [Line Items]
GuaranteedBenefitLiabilityGross, Beginning Balance							$ 2,039,178	$ 1,975,689	$ 308,149	$ 199,152	$ 1,783,594		$ 164,282		$ 10,874		$ 14,377		$ 13,377		$ 7,083		$ 177,718		$ 130,490		$ 181,195
Impact of assumption and experience unlocking and true-ups	45,603	[1]	23,648	[1]	(55,125)	[1]					0	[1]	0	[1]	0	[1]	6,948	[1]	570	[1]	1,238	[1]	38,655	[1]	23,078	[1]	(56,363)	[1]
Incurred guarantee benefits	49,999	[1]	1,680,244	[1]	211,354	[1]					9,541	[1]	1,619,312	[1]	153,408	[1]	2,873	[1]	504	[1]	5,056	[1]	37,585	[1]	60,428	[1]	52,890	[1]
GuaranteedBenefitsPaid	(32,113)		(36,352)		(47,232)						0		0		0		(682)		(74)		0		(31,431)		(36,278)		(47,232)
GuaranteedBenefitLiabilityGross, Ending Balance							$ 2,039,178	$ 1,975,689	$ 308,149	$ 199,152	$ 1,793,135		$ 1,783,594		$ 164,282		$ 23,516		$ 14,377		$ 13,377		$ 222,527		$ 177,718		$ 130,490

[1] Incurred guarantee benefits include the portion of assessments established as additions to reserve as well as changes in estimates affecting the reserves. Also includes changes in the fair value of features considered to be derivatives.