Insurance (Guarantees Related to Universal and Variable Life Contracts) (Details) - Universal and Variable Life Contracts - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Secondary Guarantees
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value (1), (3)	$ 11,398	$ 11,205
Net amount at risk (7)	$ 91,404	$ 93,028
Average attained age of policyholders	53 years	52 years
Paid-Up Guarantees
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value (1), (3)	$ 3,035	$ 3,070
Net amount at risk (7)	$ 15,279	$ 15,539
Average attained age of policyholders	64 years	64 years
Restatement Adjustment | Secondary Guarantees
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value (1), (3)		$ 2,300
Net amount at risk (7)		$ 28,900
Average attained age of policyholders		5 years
Previously Reported | Secondary Guarantees
Net Amount at Risk by Product and Guarantee [Line Items]
Total account value (1), (3)		$ 8,900
Net amount at risk (7)		$ 64,200
Average attained age of policyholders		57 years