Loans and Leases - Composition of Loan and Lease Portfolio (Parenthetical) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 42,767,551	$ 41,844,019
Deferred loan origination fees		1,700
Other Assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable		217,800	116,900
Lease Financing, Unearned Income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income		121,168	104,826
Non-Covered Loans		1,771,168	1,271,998
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1],[2]	3,416,040	3,014,378
Commercial and Industrial | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		1,644,872	1,742,380
Commercial and Industrial | Specialty Finance Loans | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		3,100,000	2,600,000
Commercial and Industrial | Other Commercial and Industrial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 394,300	$ 420,100

[1] Includes lease financing receivables, all of which were classified as Pass

[2] Includes specialty finance loans and leases of $3.1 billion and $2.6 billion, respectively, at September 30, 2020 and December 31, 2019, and other C&I loans of $394.3 million and $420.1 million, respectively, at September 30, 2020 and December 31, 2019.