Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income	$ 5,821,956	$ 3,824,778	$ 3,866,317
Noninterest income	2,356,603	2,166,994	2,088,444
Total income	8,178,559	5,991,772	5,954,761
Provision for credit losses	517,000	(75,000)	800,000
Amortization of core deposit and other intangible assets	55,624	10,167	14,869
Depreciation and other amortization	378,519	314,041	305,419
Other noninterest expense	4,616,293	3,287,415	3,064,952
Income (loss) before taxes	2,611,123	2,455,149	1,769,521
Income tax expense (benefit)	619,460	596,403	416,369
Net income (loss)	1,991,663	1,858,746	1,353,152
Average total assets	190,252,000	152,669,000	135,480,000
Capital expenditures	214,000	149,000	172,000
All Other [Member]
Segment Reporting Information [Line Items]
Net interest income	831,073	105,876	121,808
Noninterest income	963,089	746,240	725,472
Total income	1,794,162	852,116	847,280
Provision for credit losses	349,759	(313,145)	482,202
Amortization of core deposit and other intangible assets	55,624	9,107	13,809
Depreciation and other amortization	140,372	123,881	116,979
Other noninterest expense	1,522,006	1,022,786	873,367
Income (loss) before taxes	(273,599)	9,487	(639,077)
Income tax expense (benefit)	(108,547)	(10,197)	(179,965)
Net income (loss)	(165,052)	19,684	(459,112)
Average total assets	44,171,000	43,853,000	22,996,000
Capital expenditures	91,000	93,000	138,000
Business Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	712,207	518,940	462,614
Noninterest income	150,298	123,854	103,837
Total income	862,505	642,794	566,451
Provision for credit losses	17,154	10,928	25,928
Depreciation and other amortization	1,097	1,106	1,482
Other noninterest expense	421,052	350,265	329,323
Income (loss) before taxes	423,202	280,495	209,718
Income tax expense (benefit)	110,575	73,347	55,263
Net income (loss)	312,627	207,148	154,455
Average total assets	7,597,000	8,007,000	8,152,000
Capital expenditures		1,000
Commercial Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	1,338,552	832,659	827,640
Noninterest income	406,708	294,172	270,772
Total income	1,745,260	1,126,831	1,098,412
Provision for credit losses	72,200	58,064	68,232
Depreciation and other amortization	5,638	2,362	2,421
Other noninterest expense	667,282	391,568	382,822
Income (loss) before taxes	1,000,140	674,837	644,937
Income tax expense (benefit)	270,323	175,835	169,264
Net income (loss)	729,817	499,002	475,673
Average total assets	40,930,000	27,096,000	28,958,000
Capital expenditures	1,000	1,000
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Noninterest income		8,800	6,000
Average total assets		1,460,000	1,380,000
Commercial Real Estate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	736,791	665,020	710,403
Noninterest income	207,280	226,991	214,386
Total income	944,071	892,011	924,789
Provision for credit losses	(5,621)	110,401	112,077
Amortization of core deposit and other intangible assets		1,060	1,060
Depreciation and other amortization	32,900	35,623	28,187
Other noninterest expense	343,205	289,026	268,527
Income (loss) before taxes	573,587	455,901	514,938
Income tax expense (benefit)	127,604	102,259	114,485
Net income (loss)	445,983	353,642	400,453
Average total assets	30,599,000	27,091,000	27,172,000
Discretionary Portfolio [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	163,695	483,624	486,831
Noninterest income	(69,077)	(38,638)	(1,735)
Total income	94,618	444,986	485,096
Provision for credit losses	5,156	3,622	1,508
Depreciation and other amortization	111	194	285
Other noninterest expense	77,996	66,490	62,855
Income (loss) before taxes	11,355	374,680	420,448
Income tax expense (benefit)	(5,181)	87,671	99,447
Net income (loss)	16,536	287,009	321,001
Average total assets	42,657,000	22,262,000	27,726,000
Residential Mortgage Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	41,137	92,706	52,712
Noninterest income	391,127	523,765	515,549
Total income	432,264	616,471	568,261
Provision for credit losses	(1,569)	(562)	1,785
Depreciation and other amortization	67,994	57,716	60,129
Other noninterest expense	343,947	338,398	338,389
Income (loss) before taxes	21,892	220,919	167,958
Income tax expense (benefit)	964	52,251	39,006
Net income (loss)	20,928	168,668	128,952
Average total assets	3,986,000	6,463,000	4,038,000
Capital expenditures		1,000
Retail Banking [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	1,998,501	1,125,953	1,204,309
Noninterest income	307,178	290,610	260,163
Total income	2,305,679	1,416,563	1,464,472
Provision for credit losses	79,921	55,692	108,268
Depreciation and other amortization	130,407	93,159	95,936
Other noninterest expense	1,240,805	828,882	809,669
Income (loss) before taxes	854,546	438,830	450,599
Income tax expense (benefit)	223,722	115,237	118,869
Net income (loss)	630,824	323,593	331,730
Average total assets	20,312,000	17,897,000	16,438,000
Capital expenditures	$ 122,000	$ 53,000	$ 34,000