Insurance (Guarantees Related to Universal and Variable Life Contracts) (Details) - Universal and Variable Life Contracts - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Secondary Guarantees
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value (3)	$ 18,147	$ 17,689
Net amount at risk (7)	$ 170,470	$ 172,860
Average attained age of policyholders	58 years	58 years
Paid-Up Guarantees
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value (3)	$ 3,270	$ 3,337
Net amount at risk (7)	$ 17,186	$ 17,785
Average attained age of policyholders	63 years	62 years