Derivative Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivatives designated as cash flow hedges gain (loss), amount expected to be reclassified to future net income (loss), net of tax	$ 2,211	$ 2,002	$ 1,781	$ 2,065
Year by which all forecasted transactions associated with qualifying cash flow hedges are expected to occur	2057
Derivatives designated as cash flow hedges gain (loss), amount expected to be reclassified to net income in the next 12 months, net of tax	$ 131
Amount reclassified to net income in connection with forecasted transactions that were no longer considered probable of occurring	$ 15	$ 5	$ 9