Additional Information about Derivative Assets and Liabilities Subject to Enforceable Master Netting Arrangement (Parenthetical) (Detail) - Derivative assets - Subject to enforceable master netting arrangement - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Net amounts presented in the balance sheet, accruals on derivative assets	$ 1,024	$ 291
Other assets
Derivative [Line Items]
Net amounts presented in the balance sheet, accruals on derivative assets		$ 1