Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Segment Reporting Information [Line Items]
Average total assets	$ 203,492	$ 190,252	$ 180,414
Business Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	7,905	7,597	7,316
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	49,166	40,930	35,696
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Average total assets	32,000	30,599	29,032
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Average total assets	50,930	42,657	36,292
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	2,723	3,986	5,014
Retail Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	21,322	20,312	19,690
All Other [Member]
Segment Reporting Information [Line Items]
Average total assets	$ 39,446	$ 44,171	$ 47,374