Netting Arrangements for Certain Financial Instruments and Securities Financing Activities - Information on Company's Accounting Netting Adjustments and Items Not Offset in Consolidated Balance Sheet Assets But Available for Offset in Event of Default (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Offsetting [Abstract]
Cash collateral netted against derivative assets	$ 1,500	$ 429
Derivative assets not subject to netting arrangements	$ 252	$ 40

Netting Arrangements for Certain Financial Instruments and Securities Financing Activities - Information on Company's Accounting Netting Adjustments and Items Not Offset in Consolidated Balance Sheet Assets But Available for Offset in Event of Default (Parenthetical) (Detail) - USD ($)
$ in Millions

Mar. 31, 2020

Dec. 31, 2019

Cash collateral netted against derivative assets

$ 1,500

$ 429

Derivative assets not subject to netting arrangements

$ 252

$ 40