Quality of Non-Covered Loans (Excluding PCI Loans) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	$ 32,977,239
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	23,450,187
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	7,822,820
One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	105,054
Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual			935
Non-Covered Loans	308,526
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual			638
Non-Covered Loans	1,261,192	[1]
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-Covered Loans	29,460
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	6,761			6,192
Non- Accrual	63,097	[2]		76,950
Total Past Due	69,858			83,142
Current	32,907,381			32,921,219
Non-Covered Loans | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,594			464
Non- Accrual	18,779	[2]		31,089
Total Past Due	20,373			31,553
Current	23,429,814			23,800,293
Non-Covered Loans | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	3,259			1,464
Non- Accrual	23,698	[2]		24,824
Total Past Due	26,957			26,288
Current	7,795,863			7,608,032
Non-Covered Loans | One-to-four family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,244			3,086
Non- Accrual	11,270	[2]		11,032
Total Past Due	12,514			14,118
Current	92,540			124,797
Non-Covered Loans | Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non- Accrual	654	[2]		654
Total Past Due	654			654
Current	307,872			257,462
Non-Covered Loans | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	353	[1]		530	[1]
Non- Accrual	7,547	[1],[2]		8,382	[1]
Total Past Due	7,900	[1]		8,912	[1]
Current	1,253,292	[1]		1,100,309	[1]
Non-Covered Loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	311			648
Non- Accrual	1,149	[2]		969
Total Past Due	1,460			1,617
Current	$ 28,000			$ 30,326

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

[2] Excludes $2.9 million of non-covered PCI loans that were 90 days or more past due.