Non-Covered Loan Portfolio by Credit Quality Indicator (Detail) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 37,335,541	$ 35,740,489
Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		27,066,459	25,971,629
Multi-Family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		26,768,006	25,936,423
Multi-Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		271,366	6,305
Multi-Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		27,087	28,901
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		7,764,241	7,857,204
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		7,739,061	7,839,127
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		14,452	3,883
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		10,728	14,194
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		331,617	116,841
One-to-four family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		321,827	104,582
One-to-four family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		9,790	12,259
Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		372,199	311,676
Acquisition, Development and Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		348,789	309,039
Acquisition, Development and Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		17,210
Acquisition, Development and Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,200	2,637
Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		35,534,516	34,257,350
Mortgage Receivable | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		35,177,683	34,189,171
Mortgage Receivable | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		303,028	10,188
Mortgage Receivable | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		53,805	57,991
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]	1,775,295	1,450,556
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]	1,681,841	1,433,778
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]	32,156	11,771
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]	61,298	5,007
Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		19,791	24,239
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		18,423	22,996
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,368	1,243
Total Other Loans
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,795,086	1,474,795
Total Other Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,700,264	1,456,774
Total Other Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		32,156	11,771
Total Other Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 62,666	$ 6,250

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