Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Total Revenues	$ 1,982,817
Net Income (Loss)	217,522	$ 458,069	$ 579,696	$ 905,318
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		1,455,973	3,427,878	2,942,966
Business Banking [Member]
Segment Reporting Information [Line Items]
Total Revenues	203,630
Net Income (Loss)	70,536	41,607	111,647	87,878
Business Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		145,098	344,976	301,001
Business Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	726	794	1,397	1,463
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total Revenues	343,353
Net Income (Loss)	130,431	111,035	275,039	233,673
Commercial Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		284,659	632,725	570,571
Commercial Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	940	1,012	1,803	1,821
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total Revenues	239,610
Net Income (Loss)	121,737	86,690	219,347	157,962
Commercial Real Estate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		200,559	441,697	401,402
Commercial Real Estate [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	259	230	438	452
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total Revenues	89,412
Net Income (Loss)	56,085	78,532	91,470	169,078
Discretionary Portfolio [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		118,307	154,139	252,851
Discretionary Portfolio [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	(24,103)	(10,079)	(51,908)	(20,106)
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total Revenues	113,874
Net Income (Loss)	9,347	30,103	38,311	79,714
Residential Mortgage Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		146,682	251,318	300,442
Residential Mortgage Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	37,875	22,875	75,339	45,058
Retail Banking [Member]
Segment Reporting Information [Line Items]
Total Revenues	593,228
Net Income (Loss)	139,431	89,200	223,595	174,558
Retail Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		350,988	948,376	697,905
Retail Banking [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	(4)	281	(7)	553
All Other [Member]
Segment Reporting Information [Line Items]
Total Revenues	399,710
Net Income (Loss)	(310,045)	20,902	(379,713)	2,455
All Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues		209,680	654,647	418,794
All Other [Member] | Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Total Revenues	$ (15,693)	$ (15,113)	$ (27,062)	$ (29,241)