Loans Held for Sale, Loans and Allowance for Credit Losses - Summary of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	$ 119,643	$ 94,378
Provision for credit losses	82,238	11,210
Charge-offs	(33,098)	(938)
Recoveries	613	388
Balance at end of period	245,246	105,038
Allowance for credit losses, collectively evaluated for impairment	226,147	90,401
Allowance for credit losses, individually evaluated for impairment	19,099	14,637
Loans collectively evaluated	13,244,573	13,608,304
Loans individually evaluated	147,618	101,939
Loans ending balance	13,392,191	13,710,243	$ 12,983,655
Accounting Standards Update 2016-13
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	195,493
Cumulative effect of adoption of CECL	75,850
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	89,796	66,316
Provision for credit losses	63,684	9,299
Charge-offs	(31,987)	(461)
Recoveries	141	372
Balance at end of period	154,585	75,526
Allowance for credit losses, collectively evaluated for impairment	135,486	61,020
Allowance for credit losses, individually evaluated for impairment	19,099	14,506
Loans collectively evaluated	7,609,527	7,389,053
Loans individually evaluated	139,783	92,635
Loans ending balance	7,749,310	7,481,688	7,438,658
Commercial and Industrial | Accounting Standards Update 2016-13
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	122,747
Cumulative effect of adoption of CECL	32,951
Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	15,319	10,452
Provision for credit losses	17,798	102
Charge-offs	(478)	(85)
Recoveries	180
Balance at end of period	53,418	10,469
Allowance for credit losses, collectively evaluated for impairment	53,418	10,462
Allowance for credit losses, individually evaluated for impairment		7
Loans collectively evaluated	2,975,416	2,823,249
Loans individually evaluated	5,344	6,946
Loans ending balance	2,980,760	2,830,195	2,887,272
Commercial Real Estate | Accounting Standards Update 2016-13
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	35,918
Cumulative effect of adoption of CECL	20,599
Consumer
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	14,528	13,703
Provision for credit losses	756	1,206
Charge-offs	(633)	(234)
Recoveries	292	15
Balance at end of period	37,243	14,690
Allowance for credit losses, collectively evaluated for impairment	37,243	14,625
Allowance for credit losses, individually evaluated for impairment		65
Loans collectively evaluated	2,659,630	2,637,416
Loans individually evaluated	2,491	2,102
Loans ending balance	2,662,121	2,639,518	$ 2,657,725
Consumer | Accounting Standards Update 2016-13
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	36,828
Cumulative effect of adoption of CECL	22,300
Small Business Portfolio Segment
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period		3,907
Provision for credit losses		603
Charge-offs		(158)
Recoveries		1
Balance at end of period		4,353
Allowance for credit losses, collectively evaluated for impairment		4,294
Allowance for credit losses, individually evaluated for impairment		59
Loans collectively evaluated		758,586
Loans individually evaluated		256
Loans ending balance		$ 758,842
Reserve for Unfunded Commitments
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	1,699
Provision for credit losses	1,191
Balance at end of period	3,222
Reserve for Unfunded Commitments | Accounting Standards Update 2016-13
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	2,031
Cumulative effect of adoption of CECL	332
After Reserve For Unfunded Commitments
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	121,342
Provision for credit losses	83,429
Charge-offs	(33,098)
Recoveries	613
Balance at end of period	248,468
After Reserve For Unfunded Commitments | Accounting Standards Update 2016-13
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	197,524
Cumulative effect of adoption of CECL	$ 76,182