Non-Covered Loan Portfolio by Credit Quality Indicator (Detail) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 40,833,446	$ 40,133,861
Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		30,465,835	29,883,919
Multi-Family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		30,212,134	29,548,242
Multi-Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		226,488	312,025
Multi-Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		27,213	23,652
Multi-Family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,898,577	6,998,834
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,797,371	6,880,105
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		25,106	90,653
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		76,100	28,076
Commercial Real Estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		417,605	446,094
One-to-four family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		415,704	444,443
One-to-four family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		758
One-to-four family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,143	1,651
One-to-four family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
Acquisition, development, and construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		266,282	407,870
Acquisition, development, and construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		215,015	319,001
Acquisition, development, and construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		46,508	73,964
Acquisition, development, and construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		4,759	14,905
Acquisition, development, and construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		38,048,299	37,736,717
Mortgage Receivable | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		37,640,224	37,191,791
Mortgage Receivable | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		298,860	476,642
Mortgage Receivable | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		109,215	68,284
Mortgage Receivable | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	2,776,819	2,388,420	[3]
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		2,700,862	2,306,563	[3]
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,591	19,751	[3]
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		72,366	62,106	[3]
Commercial and Industrial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		8,328	8,724
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		8,064	8,469
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		264	255
Other | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]
Total Other Loans
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		2,785,147	2,397,144
Total Other Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		2,708,926	2,315,032
Total Other Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,591	19,751
Total Other Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		72,630	$ 62,361
Total Other Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans

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

[2] Includes specialty finance loans and leases of $2.3 billion and $1.9 billion, respectively, at June 30, 2019 and December 31, 2018. Other C&I loans of $456.1 million and $469.9 million, respectively, at June 30, 2019 and December 31, 2018.

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