Loans and Allowance for Credit Losses for Loans - Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 35,364,405	$ 34,153,657
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,791,390	5,847,551
Loans, deferred income, PPP	5,900	12,100
Commercial and industrial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,587,781	5,411,601
Commercial and industrial | Commercial and industrial PPP loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	203,609	435,950
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	21,937,744	20,790,066
Commercial real estate | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	19,763,202	18,935,486
Commercial real estate | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,174,542	1,854,580
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,691,935	4,545,064
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,943,336	2,970,976
Consumer | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	393,538	400,779
Consumer | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,552,928	1,570,036
Consumer | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 996,870	$ 1,000,161