Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Summary of Investments in Community Development and Tax-advantaged VIEs (Detail) - Community Development and Tax Advantaged Investments [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Investment carrying amount	$ 6,147	$ 6,148
Unfunded capital and other commitments	2,833	2,938
Maximum exposure to loss	$ 12,453	$ 12,118