Segment Reporting (Operating Results and Total Assets Reportable Segments) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total assets	$ 71,277,521	$ 34,915,599
Net interest income (expense)	2,034,286	901,089	$ 891,393
Noninterest Income	440,783	323,372	285,277
Non-interest expense	1,396,473	745,100	758,946
Pre-tax, pre-provision net revenue	1,078,596	479,361	417,724
Provision (benefit) for credit losses	280,619	(54,500)	137,750
Income (loss) before income tax expense	797,977	533,861	279,974
Income tax expense	153,694	124,997	59,353
Net income	644,283	408,864	220,621
Goodwill	2,514,104	538,373	538,373
Operating Segments [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total assets	44,380,582	15,398,159
Net interest income (expense)	1,346,384	585,297	512,691
Noninterest Income	171,437	83,538	66,867
Non-interest expense	398,100	192,977	181,218
Pre-tax, pre-provision net revenue	1,119,721	475,858	398,340
Provision (benefit) for credit losses	276,550	(51,348)	152,571
Income (loss) before income tax expense	843,171	527,206	245,769
Income tax expense	207,188	134,965	61,086
Net income	635,983	392,241	184,683
Goodwill	1,904,291	131,000
Operating Segments [Member] | HSA Bank [Member]
Segment Reporting Information [Line Items]
Total assets	122,729	73,564
Net interest income (expense)	218,149	168,595	162,363
Noninterest Income	104,586	102,814	100,826
Non-interest expense	151,329	134,258	133,919
Pre-tax, pre-provision net revenue	171,406	137,151	129,270
Provision (benefit) for credit losses	0	0	0
Income (loss) before income tax expense	171,406	137,151	129,270
Income tax expense	45,937	36,619	34,501
Net income	125,469	100,532	94,769
Goodwill	57,779	21,813
Operating Segments [Member] | Community Banking [Member]
Segment Reporting Information [Line Items]
Total assets	10,625,334	7,663,921
Net interest income (expense)	720,789	375,318	334,157
Noninterest Income	119,691	95,887	97,778
Non-interest expense	426,133	297,217	334,008
Pre-tax, pre-provision net revenue	414,347	173,988	97,927
Provision (benefit) for credit losses	(3,754)	(3,068)	(14,722)
Income (loss) before income tax expense	418,101	177,056	112,649
Income tax expense	108,657	42,139	24,956
Net income	309,444	134,917	87,693
Goodwill	552,034	385,560
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total assets	16,148,876	11,779,955
Net interest income (expense)	(251,036)	(228,121)	(117,818)
Noninterest Income	45,069	41,133	19,806
Non-interest expense	420,911	120,648	109,801
Pre-tax, pre-provision net revenue	(626,878)	(307,636)	(207,813)
Provision (benefit) for credit losses	7,823	(84)	(99)
Income (loss) before income tax expense	(634,701)	(307,552)	(207,714)
Income tax expense	(208,088)	(88,726)	(61,190)
Net income	(426,613)	(218,826)	$ (146,524)
Goodwill	$ 0	$ 0