Reinsurance - Account Value, Net Amount at Risk and Contractholders for GMDB Business (Details) - Variable Annuity [Member] - Guaranteed Minimum Death Benefit [Member] $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Contractholders	Dec. 31, 2018 USD ($) Contractholders
Guaranteed Minimum Death Benefits Account Value, Net Amount at Risk And Average Age Table [Line Items]
Account value	$ 9,110	$ 8,402
Net amount at risk	$ 1,764	$ 2,466
Average attained age of contractholders (weighted by exposure)	76 years	74 years
Number of contractholders, estimated | Contractholders	200,000	220,000