Composition of Loan and Lease Portfolio (Detail) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 41,844,019	$ 40,133,861
Net deferred loan origination costs		50,136	32,047
Allowance for losses		(147,638)	(159,820)	$ (158,046)
Total loans and leases, net		$ 41,746,517	$ 40,006,088
Non-Covered Loans, Percentage		100.00%	100.00%
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1]	$ 3,014,378	$ 2,388,420
Non-Covered Loans, Percentage	[1]	7.20%	5.95%
Commercial and Industrial | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 1,742,380	$ 1,705,308
Non-Covered Loans, Percentage		4.16%	4.25%
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 31,158,672	$ 29,883,919
Non-Covered Loans, Percentage		74.46%	74.46%
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 7,081,910	$ 6,998,834
Non-Covered Loans, Percentage		16.93%	17.44%
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 380,361	$ 446,094
Non-Covered Loans, Percentage		0.91%	1.11%
Acquisition, development, and construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 200,596	$ 407,870
Non-Covered Loans, Percentage		0.48%	1.02%
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 38,821,539	$ 37,736,717
Allowance for losses		$ (122,694)	$ (130,983)	$ (128,275)
Non-Covered Loans, Percentage		92.78%	94.03%
Lease financing, unearned income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 1,271,998	$ 683,112
Non-Covered Loans, Percentage		3.04%	1.70%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 8,102	$ 8,724
Non-Covered Loans, Percentage		0.02%	0.02%
Total Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 3,022,480	$ 2,397,144
Total Other Loans | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 3,022,480	$ 2,397,144
Non-Covered Loans, Percentage		7.22%	5.97%

[1] Includes specialty finance loans and leases of $0.0 billion and $1.9 billion, respectively, at December 30, 2019 and 2018. Other C&I loans of $000.0 million and $469.9 million, respectively, at December 30, 2019 and 2018.