Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Selected business segment financial information
Net interest income (loss)	$ 157,148	$ 162,736	$ 484,334	$ 441,755
(Provision) Benefit for credit losses	(7,500)	(3,183)	(21,300)	1,564
Net interest income after provision for credit losses	149,648	159,553	463,034	443,319
Noninterest income	46,097	45,857	142,468	131,374
Noninterest expense	(119,383)	(113,332)	(358,831)	(326,549)
Income before provision for income taxes	76,362	92,078	246,671	248,144
(Provision) benefit for income taxes	(18,141)	(23,060)	(59,190)	(62,047)
Net income	58,221	69,018	187,481	186,097
Retail Banking
Selected business segment financial information
Net interest income (loss)	119,070	117,060	332,227	318,476
(Provision) Benefit for credit losses	(2,359)	(773)	(6,913)	682
Net interest income after provision for credit losses	116,711	116,287	325,314	319,158
Noninterest income	24,834	24,480	72,898	70,280
Noninterest expense	(77,873)	(76,820)	(231,313)	(220,397)
Income before provision for income taxes	63,672	63,947	166,899	169,041
(Provision) benefit for income taxes	(15,209)	(16,093)	(39,836)	(42,139)
Net income	48,463	47,854	127,063	126,902
Commercial Banking
Selected business segment financial information
Net interest income (loss)	45,913	39,586	128,348	111,500
(Provision) Benefit for credit losses	(3,565)	(1,227)	(10,447)	701
Net interest income after provision for credit losses	42,348	38,359	117,901	112,201
Noninterest income	18,858	19,848	55,832	58,918
Noninterest expense	(24,976)	(28,079)	(79,832)	(81,546)
Income before provision for income taxes	36,230	30,128	93,901	89,573
(Provision) benefit for income taxes	(8,334)	(7,458)	(21,546)	(21,962)
Net income	27,896	22,670	72,355	67,611
Treasury and Other
Selected business segment financial information
Net interest income (loss)	(7,835)	6,090	23,759	11,779
(Provision) Benefit for credit losses	(1,576)	(1,183)	(3,940)	181
Net interest income after provision for credit losses	(9,411)	4,907	19,819	11,960
Noninterest income	2,405	1,529	13,738	2,176
Noninterest expense	(16,534)	(8,433)	(47,686)	(24,606)
Income before provision for income taxes	(23,540)	(1,997)	(14,129)	(10,470)
(Provision) benefit for income taxes	5,402	491	2,192	2,054
Net income	$ (18,138)	$ (1,506)	$ (11,937)	$ (8,416)