Quality of Loans (Excluding PCI Loans) (Detail) - USD ($) $ in Thousands		Jun. 30, 2018		Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		$ 39,418,757		$ 38,359,022
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		29,211,541		28,074,709
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		7,153,868		7,322,226
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		449,419		477,228
Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		424,827		435,825
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	[2]	2,170,439	[1]	2,040,574	[3]
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		8,663		8,460
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		56,481		73,682
Total Past Due		62,759		91,471
Current		39,355,998		38,267,551
Non-Covered Loans | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		6,278		17,789
Non-Covered Loans | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		5,408		11,078
Total Past Due		5,413		12,336
Current		29,206,128		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		5		1,258
Non-Covered Loans | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		4,917		6,659
Total Past Due		4,917		19,886
Current		7,148,951		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]
Non- Accrual		1,669		1,966
Total Past Due		1,883		2,551
Current		447,536		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		214		585
Non-Covered Loans | Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual				6,200
Total Past Due				6,200
Current		424,827		429,625
Non-Covered Loans | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual	[2]	44,483	[1]	47,768	[3]
Total Past Due	[2]	46,477	[1]	50,479	[3]
Current	[2]	2,123,962	[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]	1,994	[1]	2,711	[3]
Non-Covered Loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		4		11
Total Past Due		4,069		19
Current		4,594		8,441
Non-Covered Loans | Other | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 4,065		$ 8

[1] Includes $2.0 million and $43.5 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.