Segment Information (Summary of Segment Information) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Net interest income:
Net interest income	$ 337,804	$ 279,590	$ 637,098	$ 541,485
Net interest income, change in contribution	$ 58,214		$ 95,613
Net interest income, percent change in contribution	21.00%		18.00%
Provision for credit losses:
Provision for credit losses	$ 20,417	(15,299)	$ 24,523	(60,646)
Provision for credit losses, change in contribution	35,716		85,169
Non-interest income:
Non-interest income	102,942	129,373	265,732	315,879
Non-interest income, change in contribution	$ (26,431)		$ (50,147)
Non-interest income, percent change in contribution	(20.00%)		(16.00%)
Net revenue:
Net revenue	$ 440,746	408,963	$ 902,830	857,364
Net revenue, change in contribution	$ 31,783		$ 45,466
Net revenue, percent change in contribution	8.00%		5.00%
Segment profit:
Segment profit	$ 94,513	105,109	$ 221,904	258,257
Segment profit, change in contribution	$ (10,596)		$ (36,353)
Segment profit, percent change in contribution	(10.00%)		(14.00%)
Segment assets:
Segment assets	$ 50,969,332	46,738,450	$ 50,969,332	46,738,450	$ 50,142,143
Segment assets, change in contribution	$ 4,230,882
Segment assets, percent change in contribution	9.00%
Community banking
Segment profit:
Segment profit	$ 54,647	72,752	144,746	194,553
Segment profit, change in contribution	$ (18,105)		$ (49,807)
Segment profit, percent change in contribution	(25.00%)		(26.00%)
Segment assets:
Segment assets	$ 40,098,458	37,619,971	$ 40,098,458	37,619,971
Segment assets, change in contribution	$ 2,478,487
Segment assets, percent change in contribution	7.00%
Specialty finance
Segment profit:
Segment profit	$ 30,558	23,850	60,162	47,753
Segment profit, change in contribution	$ 6,708		$ 12,409
Segment profit, percent change in contribution	28.00%		26.00%
Segment assets:
Segment assets	$ 9,207,215	7,701,921	$ 9,207,215	7,701,921
Segment assets, change in contribution	$ 1,505,294
Segment assets, percent change in contribution	20.00%
Wealth management
Segment profit:
Segment profit	$ 9,308	8,507	16,996	15,951
Segment profit, change in contribution	$ 801		$ 1,045
Segment profit, percent change in contribution	9.00%		7.00%
Segment assets:
Segment assets	$ 1,663,659	1,416,558	$ 1,663,659	1,416,558
Segment assets, change in contribution	$ 247,101
Segment assets, percent change in contribution	17.00%
Operating Segments
Net interest income:
Net interest income	$ 329,978	272,638	622,339	528,475
Net interest income, change in contribution	$ 57,340		$ 93,864
Net interest income, percent change in contribution	21.00%		18.00%
Provision for credit losses:
Provision for credit losses	$ 20,417	(15,299)	$ 24,523	(60,646)
Provision for credit losses, change in contribution	35,716		85,169
Non-interest income:
Non-interest income	117,932	144,717	294,520	345,345
Non-interest income, change in contribution	$ (26,785)		$ (50,825)
Non-interest income, percent change in contribution	(19.00%)		(15.00%)
Net revenue:
Net revenue	$ 447,910	417,355	$ 916,859	873,820
Net revenue, change in contribution	$ 30,555		$ 43,039
Net revenue, percent change in contribution	7.00%		5.00%
Operating Segments | Community banking
Net interest income:
Net interest income	$ 261,726	219,679	$ 490,341	423,168
Net interest income, change in contribution	$ 42,047		$ 67,173
Net interest income, percent change in contribution	19.00%		16.00%
Provision for credit losses:
Provision for credit losses	$ 20,225	(15,163)	$ 24,343	(61,735)
Provision for credit losses, change in contribution	35,388		86,078
Non-interest income:
Non-interest income	62,714	90,410	184,602	237,678
Non-interest income, change in contribution	$ (27,696)		$ (53,076)
Non-interest income, percent change in contribution	(31.00%)		(22.00%)
Net revenue:
Net revenue	$ 324,440	310,089	$ 674,943	660,846
Net revenue, change in contribution	$ 14,351		$ 14,097
Net revenue, percent change in contribution	5.00%		2.00%
Operating Segments | Specialty finance
Net interest income:
Net interest income	$ 58,718	45,194	$ 114,088	90,093
Net interest income, change in contribution	$ 13,524		$ 23,995
Net interest income, percent change in contribution	30.00%		27.00%
Provision for credit losses:
Provision for credit losses	$ 192	(136)	$ 180	1,089
Provision for credit losses, change in contribution	328		$ (909)
Provision for credit losses, percent change in contribution			(83.00%)
Non-interest income:
Non-interest income	24,992	22,464	$ 49,114	45,573
Non-interest income, change in contribution	$ 2,528		$ 3,541
Non-interest income, percent change in contribution	11.00%		8.00%
Net revenue:
Net revenue	$ 83,710	67,658	$ 163,202	135,666
Net revenue, change in contribution	$ 16,052		$ 27,536
Net revenue, percent change in contribution	24.00%		20.00%
Operating Segments | Wealth management
Net interest income:
Net interest income	$ 9,534	7,765	$ 17,910	15,214
Net interest income, change in contribution	$ 1,769		$ 2,696
Net interest income, percent change in contribution	23.00%		18.00%
Provision for credit losses:
Provision for credit losses	$ 0	0	$ 0	0
Provision for credit losses, change in contribution	$ 0		$ 0
Provision for credit losses, percent change in contribution	0.00%		0.00%
Non-interest income:
Non-interest income	$ 30,226	31,843	$ 60,804	62,094
Non-interest income, change in contribution	$ (1,617)		$ (1,290)
Non-interest income, percent change in contribution	(5.00%)		(2.00%)
Net revenue:
Net revenue	$ 39,760	39,608	$ 78,714	77,308
Net revenue, change in contribution	$ 152		$ 1,406
Net revenue, percent change in contribution	0.00%		2.00%
Intersegment Eliminations
Net interest income:
Net interest income	$ 7,826	6,952	$ 14,759	13,010
Net interest income, change in contribution	$ 874		$ 1,749
Net interest income, percent change in contribution	13.00%		13.00%
Provision for credit losses:
Provision for credit losses	$ 0	0	$ 0	0
Provision for credit losses, change in contribution	$ 0		$ 0
Provision for credit losses, percent change in contribution	0.00%		0.00%
Non-interest income:
Non-interest income	$ (14,990)	(15,344)	$ (28,788)	(29,466)
Non-interest income, change in contribution	$ 354		$ 678
Non-interest income, percent change in contribution	(2.00%)		(2.00%)
Net revenue:
Net revenue	$ (7,164)	$ (8,392)	$ (14,029)	$ (16,456)
Net revenue, change in contribution	$ 1,228		$ 2,427
Net revenue, percent change in contribution	(15.00%)		(15.00%)