Insurance (Guarantees Related to Universal and Variable Life Contracts) (Details) (Universal and Variable Life Contracts [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Secondary Guarantees [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account value (general and separate account)	$ 14,743	$ 14,256
Net amount at risk	187,848	189,197
Average attained age of policyholders	55 years	54 years
Paid-Up Guarantees [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account value (general and separate account)	3,790	3,828
Net amount at risk	$ 22,835	$ 23,276
Average attained age of policyholders	60 years	60 years