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, 2012		Dec. 31, 2011
Return of net deposits
Net Amount At Risk By Product And Guarantee [Line Items]
Account value in the event of death	$ 39,883,202		$ 39,351,144
NetAmountAtRiskByProductAndGuaranteeNetAmountAtRiskInEventOfDeath	603,793		1,082,996
Average Attained Age of Contractholders In the Event of Death	63 years 0 months 0 days		62 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	8,293,324		8,237,416
NetAmountAtRiskByProductAndGuaranteeNetAmountAtRiskInEventOfDeath	1,242,583		1,673,400
Account value at annuitization or accumulation	39,685,368	[1]	38,565,164	[1]
NetAmountAtRiskByProductAndGuaranteeNetAmountAtRiskAtAnnuitization	$ 2,147,087	[1]	$ 2,870,646	[1]
Average Attained Age of Contractholders In the Event of Death	65 years 0 months 0 days		64 years 0 months 0 days
Average attained age of contractholders At Annuitization Accumulation	63 years 0 months 0 days		62 years 0 months 0 days
Average Period Remaining Until Expected Annuitization At Annuitization Accumulation	0 years 5 months 0 days		1 year 0 months 0 days

[1] Includes income and withdrawal benefits described herein