Segment Reporting (Operating Results and Total Assets Reportable Segments) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Goodwill	$ 2,631,465	$ 2,514,104	$ 2,631,465	$ 2,514,104	$ 2,514,104	$ 538,373
Assets	74,038,243		74,038,243		71,277,521
Net interest income	583,829	486,660	1,179,112	880,908
Non-interest income	89,374	120,933	160,140	224,968
Non-interest expense	344,089	358,227	676,556	718,012
Pre-tax, pre-provision net revenue	329,114	249,366	662,696	387,864
Provision for credit losses	31,498	12,243	78,247	201,088
Income before income taxes	297,616	237,123	584,449	186,776
Income tax expense	62,648	54,812	128,477	21,212
Net income	234,968	182,311	455,972	165,564
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Goodwill	2,029,204		2,029,204		1,904,291
Assets	46,426,949		46,426,949		44,380,582
Net interest income	383,606	333,421	767,920	620,490
Non-interest income	32,255	49,430	67,652	88,173
Non-interest expense	110,582	102,720	219,091	191,960
Pre-tax, pre-provision net revenue	305,279	280,131	616,481	516,703
Provision for credit losses	34,480	22,782	70,517	204,713
Income before income taxes	270,799	257,349	545,964	311,990
Income tax expense	67,971	64,337	137,037	74,392
Net income	202,828	193,012	408,927	237,598
Operating Segments | HSA Bank
Segment Reporting Information [Line Items]
Goodwill	57,485		57,485		57,779
Assets	120,295		120,295		122,729
Net interest income	75,421	49,558	147,151	94,135
Non-interest income	23,023	26,552	47,090	53,510
Non-interest expense	42,643	37,540	86,343	73,949
Pre-tax, pre-provision net revenue	55,801	38,570	107,898	73,696
Provision for credit losses	0	0	0	0
Income before income taxes	55,801	38,570	107,898	73,696
Income tax expense	15,066	10,337	29,132	19,751
Net income	40,735	28,233	78,766	53,945
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Goodwill	544,776		544,776		552,034
Assets	10,725,344		10,725,344		10,625,334
Net interest income	204,455	179,287	415,038	315,964
Non-interest income	28,877	30,798	54,836	58,699
Non-interest expense	108,880	107,366	215,759	202,876
Pre-tax, pre-provision net revenue	124,452	102,719	254,115	171,787
Provision for credit losses	769	(11,053)	2,553	(3,917)
Income before income taxes	123,683	113,772	251,562	175,704
Income tax expense	32,652	29,581	66,412	45,634
Net income	91,031	84,191	185,150	130,070
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Goodwill	0		0		0
Assets	16,765,655		16,765,655		$ 16,148,876
Net interest income	(79,653)	(75,606)	(150,997)	(149,681)
Non-interest income	5,219	14,153	(9,438)	24,586
Non-interest expense	81,984	110,601	155,363	249,227
Pre-tax, pre-provision net revenue	(156,418)	(172,054)	(315,798)	(374,322)
Provision for credit losses	(3,751)	514	5,177	292
Income before income taxes	(152,667)	(172,568)	(320,975)	(374,614)
Income tax expense	(53,041)	(49,443)	(104,104)	(118,565)
Net income	$ (99,626)	$ (123,125)	$ (216,871)	$ (256,049)