Composition of Loan Portfolio (Parenthetical) (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 40,133,861	$ 38,359,022
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1]	2,388,420	2,040,574
Commercial and Industrial | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		1,705,308	1,377,964
Lease financing, unearned income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income		53,891	65,041
Non-Covered Loans		683,112	662,610
Specialty Finance Loans | Commercial and Industrial | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		1,900,000	1,500,000
Other Commercial and Industrial Loans | Commercial and Industrial | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 469,900,000	$ 500,800,000

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