Loans and Leases - Non-Covered Loan Portfolio by Credit Quality Indicator (Detail) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 42,235,977	$ 41,844,019
Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		31,271,073	31,158,672
Multi-Family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		31,051,107	30,903,657
Multi-Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		181,529	239,664
Multi-Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		38,437	15,351
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		7,034,720	7,081,910
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,810,593	6,902,218
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		156,623	104,648
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		67,504	75,044
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		352,301	380,361
One-to-four family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		348,953	377,883
One-to-four family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,627	748
One-to-four family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,721	1,730
Acquisition, development, and construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		130,675	200,596
Acquisition, development, and construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		97,390	158,751
Acquisition, development, and construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		33,285	41,456
Acquisition, development, and construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans			389
Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]	38,788,769	38,821,539
Mortgage Receivable | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		38,308,043	38,342,509
Mortgage Receivable | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		373,064	386,516
Mortgage Receivable | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		107,662	92,514
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2],[3]	3,437,694	3,014,378
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	3,370,054	2,960,557
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	22,228	1,588
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	45,412	52,233
Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		9,514	8,102
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		9,356	7,850
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		158	252
Total Other Loans
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,447,208	3,022,480
Total Other Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,379,410	2,968,407
Total Other Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		22,228	1,588
Total Other Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 45,570	$ 52,485

[1] Excludes accrued interest receivable of $119.6 million and $116.9 million at March 31, 2020 and December 31, 2019, respectively, that is included in other assets in the Consolidated Statements of Condition.

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

[3] Includes specialty finance loans and leases of $3.0 billion and $2.6 billion, respectively, at March 31, 2020 and December 31, 2019, and other C&I loans of $432.8 million and $420.1 million, respectively, at March 31, 2020 and December 31, 2019.