Investments - Summary of Derivative Instruments Held (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Designated as Hedging Instrument | Fair Value Hedging | Foreign currency swap contracts
Derivative [Line Items]
Notional Value	$ 925
Notional value		$ 817
Designated as Hedging Instrument | Net Investment Hedging | Foreign currency swap contracts
Derivative [Line Items]
Notional Value	526
Notional value		438
Designated as Hedging Instrument | Net Investment Hedging | Foreign currency forward contracts
Derivative [Line Items]
Notional Value	636
Notional value		406
Not Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notional Value	$ 538
Notional value		$ 410