Composition of Loan Portfolio (Parenthetical) (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income		$ 43,553	$ 18,913
Non-Covered Loans		35,740,489	33,004,361
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		25,971,629	23,831,846
Multi-Family | Purchased Credit Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans			941
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		7,857,204	7,634,320
Commercial Real Estate | Purchased Credit Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans			6,000
Acquisition, Development and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		311,676	258,116
Acquisition, Development and Construction | Purchased Credit Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans			835
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1]	1,450,556	1,109,221	[2]
Commercial and Industrial | Purchased Credit Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans			436
Lease financing, unearned income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income		43,553	18,913
Non-Covered Loans		$ 365,027	208,670
Other loans | Purchased Credit Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans			$ 162

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

[2] Includes lease financing receivables, all of which were current.