Insurance (Guarantees Related to Annuity Contracts) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Variable Annuity Guarantees [Member] | Guaranteed Death Benefits [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 191,877	$ 184,095
Separate account value in event of death	152,741	143,893
Net amount at risk in event of death	6,279	9,501
Average attained age of contractholders	63 years	62 years
Variable Annuity Guarantees [Member] | Guaranteed Annuitization Benefits [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	94,429	89,137
Separate account value at annuitization	89,992	84,354
Net amount at risk at annuitization	2,978	4,593
Average attained age of contractholders	64 years	62 years
Two Tier Annuities [Member] | Guaranteed Annuitization Benefits [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	856	848
Net amount at risk at annuitization	$ 224	$ 232
Average attained age of contractholders	52 years	51 years