Non-Covered Loan Portfolio by Credit Quality Indicator (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	$ 26,813,061	$ 25,528,797
Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	18,468,229	17,430,628
Multi-Family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	18,170,382	17,135,461
Multi-Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	54,093	58,134
Multi-Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	242,263	237,033
Multi-Family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	1,491
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	7,193,194	6,855,244
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	7,089,632	6,704,824
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	31,223	64,802
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	72,339	85,618
Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	383,695	445,671
Acquisition, Development and Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	350,651	399,811
Acquisition, Development and Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	5,900	6,489
Acquisition, Development and Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	24,061	39,371
Acquisition, Development and Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	3,083
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	131,115	127,361
One-to-four family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	124,100	118,293
One-to-four family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	301
One-to-four family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	6,714	9,068
Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	26,176,233	24,858,904
Mortgage Receivable | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	25,734,765	24,358,389
Mortgage Receivable | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	91,517	129,425
Mortgage Receivable | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	345,377	371,090
Mortgage Receivable | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	4,574
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	582,572	599,986
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	540,616	570,442
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	19,772	13,234
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	22,184	15,928
Commercial and Industrial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		382
Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	54,256	69,907
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	53,263	67,808
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	993	2,099
Total Other Loan Segment
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	636,828	669,893
Total Other Loan Segment | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	593,879	638,250
Total Other Loan Segment | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	19,772	13,234
Total Other Loan Segment | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	23,177	18,027
Total Other Loan Segment | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 382