Derivative Financial Instruments - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Notional value	$ 8,800,000,000
Net derivatives	54,000,000	$ 52,000,000
Estimated accumulated other comprehensive income to be reclassified in next 12 months	19,000,000
Cash collateral held relative to derivative exposure	0	0
Cash collateral pledged	54,000,000	$ 53,000,000
CHICAGO MERCANTILE EXCHANGE
Derivative [Line Items]
Notional value	$ 8,400,000,000
Percent of total notional derivative contracts	95.10%
Amount of variation margin included as settlement	$ (218,000,000)
London Clearing House
Derivative [Line Items]
Notional value	$ 400,000,000
Percent of total notional derivative contracts	4.90%
Amount of variation margin included as settlement	$ 22,000,000