Quality of Loans (Excluding PCI Loans) (Detail) - USD ($) $ in Thousands		Mar. 31, 2018		Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		$ 38,859,854		$ 38,359,022
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		28,656,234		28,074,709
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		7,252,889		7,322,226
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		465,704		477,228
Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		441,767		435,825
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		2,035,030	[1],[2]	2,040,574	[3],[4]
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		8,230		8,460
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		73,386	[2]	73,682	[1]
Total Past Due		83,737		91,471
Current		38,776,117		38,267,551
Non-Covered Loans | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		10,351	[2]	17,789	[1]
Non-Covered Loans | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		11,881	[2]	11,078	[1]
Total Past Due		11,881		12,336
Current		28,644,353		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]			1,258
Non-Covered Loans | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		13,611	[2]	6,659	[1]
Total Past Due		16,802		19,886
Current		7,236,087		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		3,191	[2]	13,227	[1]
Non-Covered Loans | One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		1,949	[2]	1,966	[1]
Total Past Due		2,346		2,551
Current		463,358		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		397	[2]	585	[1]
Non-Covered Loans | Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual	[1]			6,200
Total Past Due				6,200
Current		441,767		429,625
Non-Covered Loans | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual	[1]	45,941	[2]	47,768	[3],[4]
Total Past Due		52,677	[1],[2]	50,479	[3],[4]
Current		1,982,353	[1],[2]	1,990,095	[3],[4]
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]	6,736	[2]	2,711	[3],[4]
Non-Covered Loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual		4	[2]	11	[1]
Total Past Due		31		19
Current		8,199		8,441
Non-Covered Loans | Other | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 27	[2]	$ 8	[1]

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

[2] Includes $6.7 million and $44.8million of taxi medallion-related loans that were 30 to 89 days past due and 90 days or more past due, respectively.

[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.

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