Segment Information (Summary of Segment Information) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Net interest income:
Net interest income	$ 401,448	$ 287,496	$ 1,038,546	$ 828,981
Net interest income, change in contribution	$ 113,952		$ 209,565
Net interest income, percent change in contribution	40.00%		25.00%
Provision for credit losses:
Provision for credit losses	$ 6,420	(7,916)	$ 30,943	(68,562)
Provision for credit losses, change in contribution	14,336		99,505
Non-interest income:
Non-interest income	101,482	136,474	367,214	452,353
Non-interest income, change in contribution	$ (34,992)		$ (85,139)
Non-interest income, percent change in contribution	(26.00%)		(19.00%)
Net revenue:
Net revenue	$ 502,930	423,970	$ 1,405,760	1,281,334
Net revenue, change in contribution	$ 78,960		$ 124,426
Net revenue, percent change in contribution	19.00%		10.00%
Segment profit:
Segment profit	$ 142,961	109,137	$ 364,865	367,394
Segment profit, change in contribution	$ 33,824		$ (2,529)
Segment profit, percent change in contribution	31.00%		(1.00%)
Segment assets:
Segment assets	$ 52,382,939	47,832,271	$ 52,382,939	47,832,271	$ 50,142,143
Segment assets, change in contribution	$ 4,550,668
Segment assets, percent change in contribution	10.00%
Community banking
Segment profit:
Segment profit	$ 104,668	68,790	249,414	263,343
Segment profit, change in contribution	$ 35,878		$ (13,929)
Segment profit, percent change in contribution	52.00%		(5.00%)
Segment assets:
Segment assets	$ 41,193,521	38,464,169	$ 41,193,521	38,464,169
Segment assets, change in contribution	$ 2,729,352
Segment assets, percent change in contribution	7.00%
Specialty finance
Segment profit:
Segment profit	$ 27,187	30,202	87,349	77,955
Segment profit, change in contribution	$ (3,015)		$ 9,394
Segment profit, percent change in contribution	(10.00%)		12.00%
Segment assets:
Segment assets	$ 9,450,977	7,918,933	$ 9,450,977	7,918,933
Segment assets, change in contribution	$ 1,532,044
Segment assets, percent change in contribution	19.00%
Wealth management
Segment profit:
Segment profit	$ 11,106	10,145	28,102	26,096
Segment profit, change in contribution	$ 961		$ 2,006
Segment profit, percent change in contribution	9.00%		8.00%
Segment assets:
Segment assets	$ 1,738,441	1,449,169	$ 1,738,441	1,449,169
Segment assets, change in contribution	$ 289,272
Segment assets, percent change in contribution	20.00%
Operating Segments
Net interest income:
Net interest income	$ 393,636	280,649	1,015,975	809,124
Net interest income, change in contribution	$ 112,987		$ 206,851
Net interest income, percent change in contribution	40.00%		26.00%
Provision for credit losses:
Provision for credit losses	$ 6,420	(7,916)	$ 30,943	(68,562)
Provision for credit losses, change in contribution	14,336		99,505
Non-interest income:
Non-interest income	116,851	152,275	411,371	497,620
Non-interest income, change in contribution	$ (35,424)		$ (86,249)
Non-interest income, percent change in contribution	(23.00%)		(17.00%)
Net revenue:
Net revenue	$ 510,487	432,924	$ 1,427,346	1,306,744
Net revenue, change in contribution	$ 77,563		$ 120,602
Net revenue, percent change in contribution	18.00%		9.00%
Operating Segments | Community banking
Net interest income:
Net interest income	$ 319,929	220,007	$ 810,270	643,175
Net interest income, change in contribution	$ 99,922		$ 167,095
Net interest income, percent change in contribution	45.00%		26.00%
Provision for credit losses:
Provision for credit losses	$ 3,608	(7,433)	$ 27,951	(69,168)
Provision for credit losses, change in contribution	11,041		97,119
Non-interest income:
Non-interest income	60,615	94,292	245,217	331,970
Non-interest income, change in contribution	$ (33,677)		$ (86,753)
Non-interest income, percent change in contribution	(36.00%)		(26.00%)
Net revenue:
Net revenue	$ 380,544	314,299	$ 1,055,487	975,145
Net revenue, change in contribution	$ 66,245		$ 80,342
Net revenue, percent change in contribution	21.00%		8.00%
Operating Segments | Specialty finance
Net interest income:
Net interest income	$ 64,122	52,659	$ 178,210	142,752
Net interest income, change in contribution	$ 11,463		$ 35,458
Net interest income, percent change in contribution	22.00%		25.00%
Provision for credit losses:
Provision for credit losses	$ 2,812	(483)	$ 2,992	606
Provision for credit losses, change in contribution	3,295		2,386
Non-interest income:
Non-interest income	23,784	24,426	72,898	69,999
Non-interest income, change in contribution	$ (642)		$ 2,899
Non-interest income, percent change in contribution	(3.00%)		4.00%
Net revenue:
Net revenue	$ 87,906	77,085	$ 251,108	212,751
Net revenue, change in contribution	$ 10,821		$ 38,357
Net revenue, percent change in contribution	14.00%		18.00%
Operating Segments | Wealth management
Net interest income:
Net interest income	$ 9,585	7,983	$ 27,495	23,197
Net interest income, change in contribution	$ 1,602		$ 4,298
Net interest income, percent change in contribution	20.00%		19.00%
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	$ 32,452	33,557	$ 93,256	95,651
Non-interest income, change in contribution	$ (1,105)		$ (2,395)
Non-interest income, percent change in contribution	(3.00%)		(3.00%)
Net revenue:
Net revenue	$ 42,037	41,540	$ 120,751	118,848
Net revenue, change in contribution	$ 497		$ 1,903
Net revenue, percent change in contribution	1.00%		2.00%
Intersegment Eliminations
Net interest income:
Net interest income	$ 7,812	6,847	$ 22,571	19,857
Net interest income, change in contribution	$ 965		$ 2,714
Net interest income, percent change in contribution	14.00%		14.00%
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	$ (15,369)	(15,801)	$ (44,157)	(45,267)
Non-interest income, change in contribution	$ 432		$ 1,110
Non-interest income, percent change in contribution	(3.00%)		(2.00%)
Net revenue:
Net revenue	$ (7,557)	$ (8,954)	$ (21,586)	$ (25,410)
Net revenue, change in contribution	$ 1,397		$ 3,824
Net revenue, percent change in contribution	(16.00%)		(15.00%)