Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net Income (Loss)	$ 646,596	$ 495,460	$ 1,226,292	$ 1,400,778
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	2,241,770	1,536,376	5,669,648	4,479,342
Business Banking [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	94,094	72,017	205,741	159,895
Business Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	241,629	181,873	586,605	482,874
Business Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	663	694	2,060	2,157
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	214,063	144,367	521,749	378,040
Commercial Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	510,549	295,209	1,239,300	865,780
Commercial Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	802	1,009	2,605	2,830
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	94,937	84,663	314,284	242,625
Commercial Real Estate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	234,479	228,317	676,176	629,719
Commercial Real Estate [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	249	227	687	679
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	11,813	74,666	103,283	243,744
Discretionary Portfolio [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	36,622	112,529	190,761	365,380
Discretionary Portfolio [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	(23,044)	(14,448)	(74,952)	(34,554)
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	(3,283)	46,077	35,028	125,791
Residential Mortgage Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	95,091	159,213	346,409	459,655
Residential Mortgage Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	35,647	25,150	110,986	70,208
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	181,639	88,004	379,688	262,562
Retail Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	650,229	357,335	1,523,992	1,055,240
Retail Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	(5)	(53)	(12)	500
All Other [Member]
Segment Reporting Information [Line Items]
Net Income (Loss)	53,333	14,334	(333,481)	11,879
All Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	473,171	201,900	1,106,405	620,694
All Other [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	$ (14,312)	$ (12,579)	$ (41,374)	$ (41,820)