Segment Information (Summary of Segment Information) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Net interest income:
Net interest income	$ 299,294	$ 261,895
Net interest income, change in contribution	$ 37,399
Net interest income, percent change in contribution	14.00%
Provision for credit losses:
Provision for credit losses	$ 4,106	(45,347)
Provision for credit losses, change in contribution	49,453
Non-interest income:
Non-interest income	162,790	186,506
Non-interest income, change in contribution	$ (23,716)
Non-interest income, percent change in contribution	(13.00%)
Net revenue:
Net revenue	$ 462,084	448,401
Net revenue, change in contribution	$ 13,683
Net revenue, percent change in contribution	3.00%
Segment profit:
Segment profit	$ 127,391	153,148
Segment profit, change in contribution	$ (25,757)
Segment profit, percent change in contribution	(17.00%)
Segment assets:
Segment assets	$ 50,250,661	45,682,202	$ 50,142,143
Segment assets, change in contribution	$ 4,568,459
Segment assets, percent change in contribution	10.00%
Community banking
Segment profit:
Segment profit	$ 90,099	121,801
Segment profit, change in contribution	$ (31,702)
Segment profit, percent change in contribution	(26.00%)
Segment assets:
Segment assets	$ 40,050,015	37,102,603
Segment assets, change in contribution	$ 2,947,412
Segment assets, percent change in contribution	8.00%
Specialty finance
Segment profit:
Segment profit	$ 29,604	23,903
Segment profit, change in contribution	$ 5,701
Segment profit, percent change in contribution	24.00%
Segment assets:
Segment assets	$ 8,624,501	7,174,269
Segment assets, change in contribution	$ 1,450,232
Segment assets, percent change in contribution	20.00%
Wealth management
Segment profit:
Segment profit	$ 7,688	7,444
Segment profit, change in contribution	$ 244
Segment profit, percent change in contribution	3.00%
Segment assets:
Segment assets	$ 1,576,145	1,405,330
Segment assets, change in contribution	$ 170,815
Segment assets, percent change in contribution	12.00%
Operating Segments
Net interest income:
Net interest income	$ 292,361	255,837
Net interest income, change in contribution	$ 36,524
Net interest income, percent change in contribution	14.00%
Provision for credit losses:
Provision for credit losses	$ 4,106	(45,347)
Provision for credit losses, change in contribution	49,453
Non-interest income:
Non-interest income	176,588	200,628
Non-interest income, change in contribution	$ (24,040)
Non-interest income, percent change in contribution	(12.00%)
Net revenue:
Net revenue	$ 468,949	456,465
Net revenue, change in contribution	$ 12,484
Net revenue, percent change in contribution	3.00%
Operating Segments | Community banking
Net interest income:
Net interest income	$ 228,615	203,489
Net interest income, change in contribution	$ 25,126
Net interest income, percent change in contribution	12.00%
Provision for credit losses:
Provision for credit losses	$ 4,118	(46,572)
Provision for credit losses, change in contribution	50,690
Non-interest income:
Non-interest income	121,888	147,268
Non-interest income, change in contribution	$ (25,380)
Non-interest income, percent change in contribution	(17.00%)
Net revenue:
Net revenue	$ 350,503	350,757
Net revenue, change in contribution	$ (254)
Net revenue, percent change in contribution	0.00%
Operating Segments | Specialty finance
Net interest income:
Net interest income	$ 55,370	44,899
Net interest income, change in contribution	$ 10,471
Net interest income, percent change in contribution	23.00%
Provision for credit losses:
Provision for credit losses	$ (12)	1,225
Provision for credit losses, change in contribution	(1,237)
Non-interest income:
Non-interest income	24,122	23,109
Non-interest income, change in contribution	$ 1,013
Non-interest income, percent change in contribution	4.00%
Net revenue:
Net revenue	$ 79,492	68,008
Net revenue, change in contribution	$ 11,484
Net revenue, percent change in contribution	17.00%
Operating Segments | Wealth management
Net interest income:
Net interest income	$ 8,376	7,449
Net interest income, change in contribution	$ 927
Net interest income, percent change in contribution	12.00%
Provision for credit losses:
Provision for credit losses	$ 0	0
Provision for credit losses, change in contribution	$ 0
Provision for credit losses, percent change in contribution	0.00%
Non-interest income:
Non-interest income	$ 30,578	30,251
Non-interest income, change in contribution	$ 327
Non-interest income, percent change in contribution	1.00%
Net revenue:
Net revenue	$ 38,954	37,700
Net revenue, change in contribution	$ 1,254
Net revenue, percent change in contribution	3.00%
Intersegment Eliminations
Net interest income:
Net interest income	$ 6,933	6,058
Net interest income, change in contribution	$ 875
Net interest income, percent change in contribution	14.00%
Provision for credit losses:
Provision for credit losses	$ 0	0
Provision for credit losses, change in contribution	$ 0
Provision for credit losses, percent change in contribution	0.00%
Non-interest income:
Non-interest income	$ (13,798)	(14,122)
Non-interest income, change in contribution	$ 324
Non-interest income, percent change in contribution	(2.00%)
Net revenue:
Net revenue	$ (6,865)	$ (8,064)
Net revenue, change in contribution	$ 1,199
Net revenue, percent change in contribution	(15.00%)