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 Liabilities But Available for Offset in Event of Default (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Offsetting [Abstract]
Cash collateral netted against derivative liabilities	$ 1,300	$ 514
Derivative liabilities not subject to netting arrangements	$ 183	$ 167

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 Liabilities But Available for Offset in Event of Default (Parenthetical) (Detail) - USD ($)
$ in Millions

Dec. 31, 2020

Dec. 31, 2019

Cash collateral netted against derivative liabilities

$ 1,300

$ 514

Derivative liabilities not subject to netting arrangements

$ 183

$ 167