Insurance (Guarantees Related to Annuity Contracts) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Variable Annuity Guarantees: | Guaranteed Death Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 55,583	$ 64,506
Separate account value (1)	34,167	41,305
Net amount at risk	$ 4,009	$ 1,572
Average attained age of contractholders	67 years	67 years
Variable Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 20,475	$ 24,036
Separate account value (1)	18,774	22,291
Net amount at risk	$ 1,131	$ 584
Average attained age of contractholders	66 years	65 years
Other Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 4,885	$ 5,671
Net amount at risk	$ 388	$ 408
Average attained age of contractholders	51 years	51 years