Off-Balance-Sheet Originate Loans and Letters of Credit (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Line Items]
Commitments	$ 2,516,434
Total loan commitments
Commitments and Contingencies Disclosure [Line Items]
Commitments	2,006,492	$ 2,000,000
Commercial, performance stand-by, and financial stand-by letters of credit
Commitments and Contingencies Disclosure [Line Items]
Commitments	509,942	$ 508,100
Total mortgage loan commitments
Commitments and Contingencies Disclosure [Line Items]
Commitments	457,979
Total mortgage loan commitments | Multi-family and commercial real estate
Commitments and Contingencies Disclosure [Line Items]
Commitments	251,679
Total mortgage loan commitments | One-to-four family
Commitments and Contingencies Disclosure [Line Items]
Commitments	801
Total mortgage loan commitments | Acquisition, development, and construction
Commitments and Contingencies Disclosure [Line Items]
Commitments	205,499
Other loan commitments
Commitments and Contingencies Disclosure [Line Items]
Commitments	$ 1,548,513