Derivative Financial Instruments - Cash Flow Hedges (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021
Derivative [Line Items]
Unrealized gain on terminated cash flow hedge remaining in AOCI, before tax	$ 132
Unrealized gain on terminated cash flow hedge remaining in AOCI, net of tax	$ 95
Term unrealized gains reclassified into earnings	4 years
Derivatives designated as hedging instruments | Interest rate swaps
Derivative [Line Items]
Derivative notional amount		$ 5,000
Derivatives net asset fair value		$ 228