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 Allowance Measurement Methodology (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	$ 79,526	$ 75,871
Collectively evaluated for credit losses	263,354	264,372
Total	342,880	340,243	$ 283,342	$ 161,759
Individually evaluated for credit losses	266,759	229,593
Collectively evaluated for credit losses	32,419,657	31,987,519
Total	32,686,416	32,217,112
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	73,574	73,063
Collectively evaluated for credit losses	52,834	58,007
Total	126,408	131,070	127,437	104,059
Individually evaluated for credit losses	144,101	131,057
Collectively evaluated for credit losses	7,004,543	6,730,651
Total	7,148,644	6,861,708
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	4,663	1,338
Collectively evaluated for credit losses	169,573	162,775
Total	174,236	164,113	111,585	45,673
Individually evaluated for credit losses	80,234	61,754
Collectively evaluated for credit losses	18,629,724	18,409,069
Total	18,709,958	18,470,823
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	773	1,206
Collectively evaluated for credit losses	26,399	27,667
Total	27,172	28,873	29,456	5,060
Individually evaluated for credit losses	39,488	35,151
Collectively evaluated for credit losses	4,021,004	4,148,592
Total	4,060,492	4,183,743
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for credit losses	516	264
Collectively evaluated for credit losses	14,548	15,923
Total	15,064	16,187	$ 14,864	$ 6,967
Individually evaluated for credit losses	2,936	1,631
Collectively evaluated for credit losses	2,764,386	2,699,207
Total	$ 2,767,322	$ 2,700,838