Segment Information - Summary of Segment Reporting Information (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 214,903		$ 186,517		$ 406,405	$ 377,477
Provision for credit losses	(1,807)		(8,879)		(5,217)	(8,736)
Other income	43,608		62,864		89,633	155,444
Other expense	141,174		138,969		280,349	287,903
Income taxes	23,531		24,455		43,629	52,020
Net income	95,613	$ 81,664	94,836	$ 106,898	177,277	201,734
Total assets (liabilities)	28,777,896		27,190,926		28,777,896	27,190,926
Average assets (liabilities)	29,009,448		27,005,958		29,176,491	26,750,101
Operating Segments [Member] | Community Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	211,592		183,400		401,274	370,597
Provision for credit losses	(1,807)		(8,879)		(5,217)	(8,736)
Other income	26,899		24,090		51,800	50,485
Other expense	119,249		103,447		233,788	213,471
Income taxes	23,907		23,149		44,336	44,351
Net income	97,142		89,773		180,167	171,996
Total assets (liabilities)	28,444,813		26,831,380		28,444,813	26,831,380
Average assets (liabilities)	28,680,546		26,661,453		28,851,275	26,409,142
Operating Segments [Member] | Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	2,870		2,871		5,187	5,521
Provision for credit losses	0		0		0	0
Other income	21,468		39,765		44,865	107,272
Other expense	25,776		36,391		51,224	77,574
Income taxes	(285)		1,280		(228)	7,220
Net income	(1,153)		4,965		(944)	27,999
Total assets (liabilities)	477,673		720,912		477,673	720,912
Average assets (liabilities)	488,230		729,114		481,773	722,997
Other [Member]
Segment Reporting Information [Line Items]
Net interest income	(2,662)		(2,106)		(4,787)	(4,244)
Provision for credit losses	0		0		0	0
Other income	2,222		1,132		2,162	2,653
Other expense	27		(1,098)		(200)	(3,779)
Income taxes	(91)		26		(479)	449
Net income	(376)		98		(1,946)	1,739
Total assets (liabilities)	42,074		32,619		42,074	32,619
Average assets (liabilities)	30,511		26,090		32,358	24,709
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income	3,103		2,352		4,731	5,603
Provision for credit losses	0		0		0	0
Other income	(6,981)		(2,123)		(9,194)	(4,966)
Other expense	(3,878)		229		(4,463)	637
Income taxes	0		0		0	0
Net income	0		0		0	0
Total assets (liabilities)	(186,664)		(393,985)		(186,664)	(393,985)
Average assets (liabilities)	$ (189,839)		$ (410,699)		$ (188,915)	$ (406,747)