Insurance (Guarantees Related to Annuity Contracts) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Variable Annuity Guarantees: | Guaranteed Death Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 66,192	$ 63,381
Separate account value (1)	41,540	38,888
Net amount at risk	$ 2,027	$ 3,197
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	$ 24,409	$ 23,174
Separate account value (1)	22,632	21,385
Net amount at risk	$ 424	$ 511
Average attained age of contractholders	65 years	64 years
Other Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value	$ 5,825	$ 5,787
Net amount at risk	$ 530	$ 549
Average attained age of contractholders	50 years	50 years
Restatement Adjustment | Variable Annuity Guarantees: | Guaranteed Death Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value		$ 7,100
Separate account value (1)		1,500
Net amount at risk		429
Restatement Adjustment | Variable Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value		1,500
Separate account value (1)		1,500
Net amount at risk		$ 28
Average attained age of contractholders		1 year
Restatement Adjustment | Other Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value		$ 4,500
Net amount at risk		60
Previously Reported | Variable Annuity Guarantees: | Guaranteed Death Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value		56,200
Separate account value (1)		37,300
Net amount at risk		2,800
Previously Reported | Variable Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value		21,600
Separate account value (1)		19,800
Net amount at risk		$ 483
Average attained age of contractholders		65 years
Previously Reported | Other Annuity Guarantees: | Guaranteed Annuitization Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value		$ 1,300
Net amount at risk		$ 489