Insurance (Guarantees Related to Annuity Contracts) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Variable Annuity Guarantees: | Guaranteed Death Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 183,010	$ 181,413
Separate account value	153,486	151,901
Net amount at risk	$ 8,157	$ 10,339
Average attained age of contractholders	66 years	66 years
Variable Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 92,187	$ 91,240
Separate account value	88,546	87,841
Net amount at risk	$ 4,663	$ 2,762
Average attained age of contractholders	66 years	66 years
Other Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 1,600	$ 1,560
Net amount at risk	$ 576	$ 422
Average attained age of contractholders	50 years	51 years