Certain Nontraditional Long-Duration Contracts and Variable Annuity Guarantees - Separate Account Balances (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Separate Account Investment [Line Items]
Total	$ 209,135.8	$ 193,903.6
Equity
Fair Value, Separate Account Investment [Line Items]
Total	145,386.1	132,213.0
Bond
Fair Value, Separate Account Investment [Line Items]
Total	20,211.3	20,202.9
Balanced
Fair Value, Separate Account Investment [Line Items]
Total	41,708.4	39,626.1
Money market
Fair Value, Separate Account Investment [Line Items]
Total	$ 1,830.0	$ 1,861.6