Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Selected business segment financial information
Net interest income (expense)	$ 145,147	$ 131,481	$ 279,019	$ 260,639
Benefit (Provision) for credit losses	(1,000)	35,000	4,747	35,000
Net interest income after provision for credit losses	144,147	166,481	283,766	295,639
Noninterest income	44,137	49,371	85,517	93,239
Noninterest expense	(109,175)	(99,388)	(213,217)	(195,694)
Income before provision for income taxes	79,109	116,464	156,066	193,184
(Provision) benefit for income taxes	(19,749)	(29,723)	(38,987)	(48,750)
Net income	59,360	86,741	117,079	144,434
Total assets	25,377,533		25,377,533		$ 24,992,410
Retail Banking
Selected business segment financial information
Net interest income (expense)	107,368	97,106	201,416	191,560
Benefit (Provision) for credit losses	(386)	12,654	1,455	14,124
Net interest income after provision for credit losses	106,982	109,760	202,871	205,684
Noninterest income	22,485	22,495	45,800	46,070
Noninterest expense	(73,357)	(62,115)	(143,577)	(125,004)
Income before provision for income taxes	56,110	70,140	105,094	126,750
(Provision) benefit for income taxes	(13,896)	(17,884)	(26,046)	(32,010)
Net income	42,214	52,256	79,048	94,740
Commercial Banking
Selected business segment financial information
Net interest income (expense)	36,826	40,234	71,914	78,500
Benefit (Provision) for credit losses	(614)	17,465	1,928	19,495
Net interest income after provision for credit losses	36,212	57,699	73,842	97,995
Noninterest income	20,415	19,528	39,070	35,569
Noninterest expense	(26,962)	(24,993)	(53,467)	(47,471)
Income before provision for income taxes	29,665	52,234	59,445	86,093
(Provision) benefit for income taxes	(7,251)	(13,285)	(14,504)	(21,629)
Net income	22,414	38,949	44,941	64,464
Treasury and Other
Selected business segment financial information
Net interest income (expense)	953	(5,859)	5,689	(9,421)
Benefit (Provision) for credit losses		4,881	1,364	1,381
Net interest income after provision for credit losses	953	(978)	7,053	(8,040)
Noninterest income	1,237	7,348	647	11,600
Noninterest expense	(8,856)	(12,280)	(16,173)	(23,219)
Income before provision for income taxes	(6,666)	(5,910)	(8,473)	(19,659)
(Provision) benefit for income taxes	1,398	1,446	1,563	4,889
Net income	$ (5,268)	$ (4,464)	$ (6,910)	$ (14,770)