Loans, Leases and Allowance for Credit Losses - Allowances for Credit Losses (Detail) Valuation - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 310,560	$ 165,021	$ 310,560	$ 165,021	$ 310,550	$ 186,925		$ 160,409	$ 152,717
Provision for Loan and Lease Losses	(8,204)	(4,000)	(134,130)	(14,500)
Financing Receivable, Allowance for Credit Loss, Writeoff	8,773	2,099	14,593	6,968
Financing Receivable, Allowance for Credit Loss, Recovery	(579)	(2,711)	(4,098)	(4,772)
Financing Receivable, Collectively Evaluated for Impairment	25,654,269		25,654,269				$ 20,932,161
Financing Receivable, Individually Evaluated for Impairment	338,985		338,985				116,303
Loans and Leases Receivable, Net of Deferred Income	25,993,254		25,993,254				21,101,493
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	300,514		300,514				164,923
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	10,046		10,046				2,776
Impaired Financing Receivable, with Related Allowance, Recorded Investment							20,979
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							95,324
Off-Balance Sheet, Credit Loss, Liability	44,400		44,400				8,955
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							24,055
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							99,440
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							123,495
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							20,921,137
Financing Receivable Unpaid Principal Balance							21,108,472
Impaired Financing Receivable, Related Allowance							2,776
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance	310,560		310,560				167,797
Interest Receivable	120,100		120,100
Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							53,029
Impaired Financing Receivable, Unpaid Principal Balance							63,840
Impaired Financing Receivable, Related Allowance							98
Commercial and industrial [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss		77,419		77,419				79,635	83,118
Provision for Loan and Lease Losses		(2,815)		(3,128)
Financing Receivable, Allowance for Credit Loss, Writeoff		1,950		6,092
Financing Receivable, Allowance for Credit Loss, Recovery		(2,549)		(3,521)
Financing Receivable, Collectively Evaluated for Impairment							9,333,059
Financing Receivable, Individually Evaluated for Impairment							48,984
Loans and Leases Receivable, Net of Deferred Income							9,382,043
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment							81,252
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment							1,050
Impaired Financing Receivable, with Related Allowance, Recorded Investment							6,919
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							42,065
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							9,844
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							43,848
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							53,692
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							9,312,100
Financing Receivable Unpaid Principal Balance							9,365,792
Impaired Financing Receivable, Related Allowance							1,050
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance							82,302
Commercial and industrial [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							0
Impaired Financing Receivable, Unpaid Principal Balance							0
Impaired Financing Receivable, Related Allowance							0
Tech & Innovation [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	38,836		38,836		54,559	22,394
Provision for Loan and Lease Losses	(9,359)		(25,556)
Financing Receivable, Allowance for Credit Loss, Writeoff	6,364		9,114
Financing Receivable, Allowance for Credit Loss, Recovery	0		0
Financing Receivable, Collectively Evaluated for Impairment	2,227,995		2,227,995
Financing Receivable, Individually Evaluated for Impairment	49,894		49,894
Loans and Leases Receivable, Net of Deferred Income	2,277,889		2,277,889
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	38,836		38,836
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0
Other commercial and industrial [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	108,753		108,753		109,930	95,784
Provision for Loan and Lease Losses	(621)		(13,653)
Financing Receivable, Allowance for Credit Loss, Writeoff	748		2,684
Financing Receivable, Allowance for Credit Loss, Recovery	(192)		(2,000)
Financing Receivable, Collectively Evaluated for Impairment	5,906,731		5,906,731
Financing Receivable, Individually Evaluated for Impairment	86,981		86,981
Loans and Leases Receivable, Net of Deferred Income	5,993,712		5,993,712
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	102,011		102,011
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	6,742		6,742
Commercial Real Estate Owner Occupied [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	19,406		19,406		15,587	10,420
Provision for Loan and Lease Losses	(3,897)		(9,100)
Financing Receivable, Allowance for Credit Loss, Writeoff	83		126
Financing Receivable, Allowance for Credit Loss, Recovery	(5)		(12)
Financing Receivable, Collectively Evaluated for Impairment	1,912,127		1,912,127				2,296,342
Financing Receivable, Individually Evaluated for Impairment	58,036		58,036				17,736
Loans and Leases Receivable, Net of Deferred Income	1,970,163		1,970,163				2,316,913
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	19,406		19,406				13,842
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0				0
Impaired Financing Receivable, with Related Allowance, Recorded Investment							0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							17,736
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							18,681
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							18,681
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							2,297,168
Financing Receivable Unpaid Principal Balance							2,319,426
Impaired Financing Receivable, Related Allowance							0
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance							13,842
Commercial Real Estate Owner Occupied [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							2,835
Impaired Financing Receivable, Unpaid Principal Balance							3,577
Impaired Financing Receivable, Related Allowance							0
Commercial Real Estate Non Owner Occupied [Member]
Valuation Allowance [Line Items]
Financing Receivable, Collectively Evaluated for Impairment							5,159,921
Financing Receivable, Individually Evaluated for Impairment							35,538
Loans and Leases Receivable, Net of Deferred Income							5,245,634
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment							32,114
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment							1,219
Impaired Financing Receivable, with Related Allowance, Recorded Investment							11,913
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							23,625
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							11,949
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							24,738
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							36,687
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							5,177,477
Financing Receivable Unpaid Principal Balance							5,274,355
Impaired Financing Receivable, Related Allowance							1,219
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance							33,431
Commercial Real Estate Non Owner Occupied [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							50,175
Impaired Financing Receivable, Unpaid Principal Balance							60,191
Impaired Financing Receivable, Related Allowance							98
Hotel franchise finance [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	38,027		38,027		35,864	14,104
Provision for Loan and Lease Losses	(2,163)		(23,923)
Financing Receivable, Allowance for Credit Loss, Writeoff	0		0
Financing Receivable, Allowance for Credit Loss, Recovery	0		0
Financing Receivable, Collectively Evaluated for Impairment	1,885,451		1,885,451
Financing Receivable, Individually Evaluated for Impairment	57,435		57,435
Loans and Leases Receivable, Net of Deferred Income	1,942,886		1,942,886
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	35,312		35,312
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	2,715		2,715
Other Commercial Real Estate Non owner Occupied [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	40,622		40,622		32,672	10,503
Provision for Loan and Lease Losses	(9,196)		(30,684)
Financing Receivable, Allowance for Credit Loss, Writeoff	1,246		2,131
Financing Receivable, Allowance for Credit Loss, Recovery	0		(1,566)
Financing Receivable, Collectively Evaluated for Impairment	3,355,259		3,355,259
Financing Receivable, Individually Evaluated for Impairment	78,673		78,673
Loans and Leases Receivable, Net of Deferred Income	3,433,932		3,433,932
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	40,518		40,518
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	104		104
Residential Real Estate [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	1,789	13,532	1,789	13,532	1,725	3,814		12,606	11,276
Provision for Loan and Lease Losses	(16)	(804)	(2,103)	(2,599)
Financing Receivable, Allowance for Credit Loss, Writeoff	307	9	307	594
Financing Receivable, Allowance for Credit Loss, Recovery	(355)	(131)	(385)	(251)
Financing Receivable, Collectively Evaluated for Impairment	2,324,676		2,324,676				2,142,045
Financing Receivable, Individually Evaluated for Impairment	5,388		5,388				5,600
Loans and Leases Receivable, Net of Deferred Income	2,330,064		2,330,064				2,147,664
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,789		1,789				13,714
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0				0
Impaired Financing Receivable, with Related Allowance, Recorded Investment							0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							5,600
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							5,708
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							5,708
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							2,113,893
Financing Receivable Unpaid Principal Balance							2,119,673
Impaired Financing Receivable, Related Allowance							0
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance							13,714
Residential Real Estate [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							19
Impaired Financing Receivable, Unpaid Principal Balance							72
Impaired Financing Receivable, Related Allowance							0
Construction And Land Development [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	38,781	27,318	38,781	27,318	35,792	6,218		26,091	22,513
Provision for Loan and Lease Losses	(2,983)	(1,210)	(32,540)	(4,865)
Financing Receivable, Allowance for Credit Loss, Writeoff	0	0	0	141
Financing Receivable, Allowance for Credit Loss, Recovery	(6)	(17)	(23)	(81)
Financing Receivable, Collectively Evaluated for Impairment	2,267,922		2,267,922				1,943,735
Financing Receivable, Individually Evaluated for Impairment	0		0				8,421
Loans and Leases Receivable, Net of Deferred Income	2,267,922		2,267,922				1,952,156
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	38,781		38,781				23,387
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0				507
Impaired Financing Receivable, with Related Allowance, Recorded Investment							2,147
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							6,274
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							2,262
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							6,413
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							8,675
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							1,963,116
Financing Receivable Unpaid Principal Balance							1,971,791
Impaired Financing Receivable, Related Allowance							507
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance							23,894
Construction And Land Development [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							0
Impaired Financing Receivable, Unpaid Principal Balance							0
Impaired Financing Receivable, Related Allowance							0
Warehouse lending [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	838		838		743	246
Provision for Loan and Lease Losses	(95)		(592)
Financing Receivable, Allowance for Credit Loss, Writeoff	0		0
Financing Receivable, Allowance for Credit Loss, Recovery	0		0
Financing Receivable, Collectively Evaluated for Impairment	3,926,852		3,926,852
Financing Receivable, Individually Evaluated for Impairment	0		0
Loans and Leases Receivable, Net of Deferred Income	3,926,852		3,926,852
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	838		838
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0
Municipal and nonprofit [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	17,896		17,896		17,128	17,397
Provision for Loan and Lease Losses	(768)		(499)
Financing Receivable, Allowance for Credit Loss, Writeoff	0		0
Financing Receivable, Allowance for Credit Loss, Recovery	0		0
Financing Receivable, Collectively Evaluated for Impairment	1,684,738		1,684,738
Financing Receivable, Individually Evaluated for Impairment	1,952		1,952
Loans and Leases Receivable, Net of Deferred Income	1,686,690		1,686,690
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	17,454		17,454
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	442		442
Other, loan segment
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss	5,612		5,612		$ 6,550	$ 6,045
Provision for Loan and Lease Losses	(934)		(314)
Financing Receivable, Allowance for Credit Loss, Writeoff	25		231
Financing Receivable, Allowance for Credit Loss, Recovery	(21)		(112)
Financing Receivable, Collectively Evaluated for Impairment	162,518		162,518
Financing Receivable, Individually Evaluated for Impairment	626		626
Loans and Leases Receivable, Net of Deferred Income	163,144		163,144
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	5,569		5,569
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	$ 43		$ 43
Commercial Real Estate [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss		45,944		45,944				41,258	34,829
Provision for Loan and Lease Losses		(4,817)		(10,354)
Financing Receivable, Allowance for Credit Loss, Writeoff		139		139
Financing Receivable, Allowance for Credit Loss, Recovery		(8)		(900)
Commercial Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Valuation Allowance [Line Items]
Loans and Leases Receivable, Net of Deferred Income							2,316,913
Commercial Real Estate [Member] | Commercial Real Estate Non Owner Occupied [Member]
Valuation Allowance [Line Items]
Loans and Leases Receivable, Net of Deferred Income							5,024,218
Consumer Loan [Member]
Valuation Allowance [Line Items]
Financing Receivable, Allowance for Credit Loss		808		808				$ 819	$ 981
Provision for Loan and Lease Losses		(16)		(190)
Financing Receivable, Allowance for Credit Loss, Writeoff		1		2
Financing Receivable, Allowance for Credit Loss, Recovery		$ (6)		$ (19)
Financing Receivable, Collectively Evaluated for Impairment							57,059
Financing Receivable, Individually Evaluated for Impairment							24
Loans and Leases Receivable, Net of Deferred Income							57,083
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment							614
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment							0
Impaired Financing Receivable, with Related Allowance, Recorded Investment							0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment							24
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance							0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance							52
Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment							52
Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment							57,383
Financing Receivable Unpaid Principal Balance							57,435
Impaired Financing Receivable, Related Allowance							0
Impaired Financing Receivable With No Related Allowance							0
Loans and Leases Receivable, Allowance							614
Consumer Loan [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Valuation Allowance [Line Items]
Impaired Financing Receivable, Recorded Investment							0
Impaired Financing Receivable, Unpaid Principal Balance							0
Impaired Financing Receivable, Related Allowance							$ 0