Loans and Allowance for Credit Losses for Loans - Summary of Allocation of Allowance for Loan Losses and Related Loans by Loan Portfolio Segment Disaggregated Based on Impairment Methodology (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	$ 75,871	$ 38,576
Collectively evaluated for credit losses	264,372	123,183
Allowance for loan losses	340,243	161,759	$ 151,859
Individually evaluated for credit losses	229,593	163,644
Collectively evaluated for credit losses	31,987,519	22,905,965
Loans	32,217,112	29,699,208
Loans acquired with discounts related to credit quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		6,629,599
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	73,063	36,662
Collectively evaluated for credit losses	58,007	67,397
Allowance for loan losses	131,070	104,059	90,956
Individually evaluated for credit losses	131,057	100,860
Collectively evaluated for credit losses	6,730,651	4,043,123
Loans	6,861,708	4,825,997
Commercial and industrial | Loans acquired with discounts related to credit quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		682,014
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	1,338	1,338
Collectively evaluated for credit losses	162,775	44,335
Allowance for loan losses	164,113	45,673	49,650
Individually evaluated for credit losses	61,754	51,242
Collectively evaluated for credit losses	18,409,069	12,347,368
Loans	18,470,823	17,643,759
Commercial real estate | Loans acquired with discounts related to credit quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		5,245,149
Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	1,206	518
Collectively evaluated for credit losses	27,667	4,542
Allowance for loan losses	28,873	5,060	5,041
Individually evaluated for credit losses	35,151	10,689
Collectively evaluated for credit losses	4,148,592	3,786,253
Loans	4,183,743	4,377,111
Residential mortgage | Loans acquired with discounts related to credit quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		580,169
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	264	58
Collectively evaluated for credit losses	15,923	6,909
Allowance for loan losses	16,187	6,967	$ 6,212
Individually evaluated for credit losses	1,631	853
Collectively evaluated for credit losses	2,699,207	2,729,221
Loans	$ 2,700,838	2,852,341
Consumer | Loans acquired with discounts related to credit quality
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		$ 122,267