Quality of Non-Covered Loans (Excluding PCI Loans) (Detail) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		$ 40,133,861		$ 38,359,022
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		29,883,919		28,074,709
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		6,998,834		7,322,226
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		446,094		477,228
Acquisition, development, and construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		407,870		435,825
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	[2]	2,388,420	[1]	2,040,574	[3]
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		8,724		8,460
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		46,070		91,471
Non- Accrual		45,506		73,682
Current		40,087,791		38,267,551
Non-Covered Loans | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		564		17,789
Non-Covered Loans | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		4,220		12,336
Non- Accrual		4,220		11,078
Current		29,879,699		28,062,373
Non-Covered Loans | Multi-Family | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due				1,258
Non-Covered Loans | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		3,021		19,886
Non- Accrual		3,021		6,659
Current		6,995,813		7,302,340
Non-Covered Loans | Commercial Real Estate | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due				13,227
Non-Covered Loans | One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,660		2,551
Non- Accrual		1,651		1,966
Current		444,434		474,677
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		9		585
Non-Covered Loans | Acquisition, development, and construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due				6,200
Non- Accrual				6,200
Current		407,870		429,625
Non-Covered Loans | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[2]	37,138	[1]	50,479	[3]
Non- Accrual	[2]	36,608	[1]	47,768	[3]
Current	[2]	2,351,282	[1]	1,990,095	[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	[2]	530	[1]	2,711	[3]
Non-Covered Loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		31		19
Non- Accrual		6		11
Current		8,693		8,441
Non-Covered Loans | Other | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 25		$ 8

[1] 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.

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

[3] Includes $2.7 million and $46.7 million of taxi medallion-related loans that were 30 to 89 days past due and 90 days or more past due, respectively.