Quality of Non-Covered Loans (Excluding PCI Loans and Leases) (Detail) - USD ($) $ in Thousands		Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		$ 40,833,446		$ 40,133,861
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		30,465,835		29,883,919
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		6,898,577		6,998,834
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		417,605		446,094
Acquisition, development, and construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		266,282		407,870
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		3,300				$ 1,700
Non-Covered Loans	[2]	2,776,819	[1]	2,388,420	[3]
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		8,328		8,724
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		55,703		46,070
Non- Accrual		51,414		45,506
Current		40,777,743		40,087,791
Non-Covered Loans | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		4,289		564
Non-Covered Loans | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		5,218		4,220
Non- Accrual		3,906		4,220
Current		30,460,617		29,879,699
Non-Covered Loans | Multi-Family | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,312
Non-Covered Loans | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		2,993		3,021
Non- Accrual		2,993		3,021
Current		6,895,584		6,995,813
Non-Covered Loans | One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		3,012		1,660
Non- Accrual		1,143		1,651
Current		414,593		444,434
Non-Covered Loans | One-to-four family | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,869		9
Non-Covered Loans | Acquisition, development, and construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current		266,282		407,870
Non-Covered Loans | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		44,441	[1],[2]	37,138
Non- Accrual		43,357	[1],[2]	36,608
Current	[2]	2,732,378	[1]	2,351,282	[3]
Non-Covered Loans | Commercial and Industrial | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,084	[1],[2]	530
Non-Covered Loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		39		31
Non- Accrual		15		6
Current		8,289		8,693
Non-Covered Loans | Other | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 24		$ 25

[1] Includes $204,000 and $32.9 million of taxi medallion-related loans that were 30 to 89 days past due and 90 days or more past due, respectively.

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

[3] Includes $530,000 and $35.5 million of taxi medallion-related loans that were 30 to 89 days past due and 90 days or more past due, respectively.