Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Segment Reporting Information [Line Items]
Average Total Assets	$ 180,414	$ 152,669	$ 149,406
Business Banking [Member]
Segment Reporting Information [Line Items]
Average Total Assets	7,316	8,007	8,681
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Average Total Assets	31,632	28,559	29,927
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Average Total Assets	27,784	25,628	25,999
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Average Total Assets	36,292	22,262	22,769
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Average Total Assets	5,014	6,463	6,638
Retail Banking [Member]
Segment Reporting Information [Line Items]
Average Total Assets	24,411	17,897	17,444
All Other [Member]
Segment Reporting Information [Line Items]
Average Total Assets	$ 47,965	$ 43,853	$ 37,948