Segment Information - Summary of Segment Information (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Segment Reporting Information [Line Items]
Average total assets	$ 202,599	$ 190,252	$ 151,648
Business Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	7,825	7,597	6,568
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	48,222	40,930	26,329
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Average total assets	32,171	30,599	23,939
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Average total assets	50,501	42,657	22,899
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	2,605	3,986	6,250
Retail Banking [Member]
Segment Reporting Information [Line Items]
Average total assets	21,421	20,312	18,610
All Other [Member]
Segment Reporting Information [Line Items]
Average total assets	$ 39,854	$ 44,171	$ 47,053