Quality of Non-Covered Loans (Excluding PCI Loans) (Detail) - USD ($) $ in Thousands		Dec. 31, 2017		Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		$ 38,359,022		$ 37,350,439
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		28,074,709		26,945,052
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		7,322,226		7,724,362
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		477,228		381,081
Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		435,825		381,194
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	[2]	2,040,574	[1]	1,900,445	[3]
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans		8,460		18,305	[4]
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		91,471		66,852
Non- Accrual	[2]	73,682		56,469
Current		38,267,551		37,283,587
Non-Covered Loans | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[2]	17,789		10,383
Non-Covered Loans | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		12,336		13,586
Non- Accrual	[2]	11,078		13,558
Current		28,062,373		26,931,466
Non-Covered Loans | Multi-Family | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[2]	1,258		28
Non-Covered Loans | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		19,886		9,297
Non- Accrual	[2]	6,659		9,297
Current		7,302,340		7,715,065
Non-Covered Loans | Commercial Real Estate | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[2]	13,227
Non-Covered Loans | One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		2,551		12,523
Non- Accrual	[2]	1,966		9,679
Current		474,677		368,558
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	[2]	585		2,844
Non-Covered Loans | Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		6,200		6,200
Non- Accrual	[2]	6,200		6,200
Current		429,625		374,994
Non-Covered Loans | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[2]	50,479	[1]	23,685	[3]
Non- Accrual	[2]	47,768	[1]	16,422	[3]
Current	[2]	1,990,095	[1]	1,876,760	[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]	2,711	[1]	7,263	[3]
Non-Covered Loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		19		1,561	[4]
Non- Accrual	[2]	11		1,313	[4]
Current		8,441		16,744	[4]
Non-Covered Loans | Other | Financing Receivable, 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[2]	$ 8		$ 248	[4]

[1] (1) 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.

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

[3] (1) Excludes $6 thousand and $869 thousand of non-covered PCI loans that were 30 to 89 days past due and 90 days or more past due, resp

[4] (3) Includes $6.8 million and $15.2 million of taxi medallion loans that were 30 to 89 days past due and 90 days or more past due, respectively.