Certain Nontraditional Long-Duration Contracts (Guarantees Associated with Variable Annuity Contracts, by Guarantee Type) (Details) (variableannuity, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Net Amount At Risk By Product And Guarantee [Line Items]
Average Period Remaining Until Expected Annuitization At Annuitization Accumulation	0 years 1 month 0 days		0 years 2 months 0 days
Return of net deposits
Net Amount At Risk By Product And Guarantee [Line Items]
Account value in the event of death	38,410,155		40,828,166
NetAmountAtRiskByProductAndGuaranteeNetAmountAtRiskInEventOfDeath	353,902		407,488
Average Attained Age of Contractholders In the Event of Death	65 years 0 months 0 days		64 years 0 months 0 days
Minimum return or contract value
Net Amount At Risk By Product And Guarantee [Line Items]
Account value in the event of death	7,886,833		8,446,938
NetAmountAtRiskByProductAndGuaranteeNetAmountAtRiskInEventOfDeath	916,016		916,094
Account value at annuitization or accumulation	38,471,465	[1]	40,678,507	[1]
NetAmountAtRiskByProductAndGuaranteeNetAmountAtRiskAtAnnuitization	1,358,023	[1]	1,272,641	[1]
Average Attained Age of Contractholders In the Event of Death	67 years 0 months 0 days		66 years 0 months 0 days
Average attained age of contractholders At Annuitization Accumulation	64 years 0 months 0 days		64 years 0 months 0 days

[1] Includes income and withdrawal benefits described herein.