Derivative Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Notional derivative contracts	$ 8,600
Net positive exposure	43	$ 52
Estimated reclassification of AOCI to interest expense	19
Cash collateral pledged	43	$ 53
CME
Derivative [Line Items]
Notional derivative contracts	$ 8,200
Notional derivative contracts, percent	95.30%
Amount of variation margin included as settlement	$ (179)
LCH
Derivative [Line Items]
Notional derivative contracts	$ 400
Notional derivative contracts, percent	4.70%
Amount of variation margin included as settlement	$ 19