Composition of Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	$ 26,813,061	$ 25,528,797
Net deferred loan origination costs	9,789	4,021
Non-Covered Loans, Percentage	100.00%	100.00%
Allowance for losses on non-covered loans	(139,015)	(137,290)
Non-covered loans held for investment, net	26,683,835	25,395,528
Covered loans	3,400,624	3,753,031
Allowance for losses on covered loans	(54,591)	(33,323)
Total covered loans, net	3,346,033	3,719,708
Loans held for sale	1,211,767	1,036,918
Total loans, net	31,241,635	30,152,154
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	18,468,229	17,430,628
Non-Covered Loans, Percentage	68.88%	68.28%
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	7,193,194	6,855,244
Non-Covered Loans, Percentage	26.83%	26.85%
Acquisition, Development and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	383,695	445,671
Non-Covered Loans, Percentage	1.43%	1.75%
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	131,115	127,361
Non-Covered Loans, Percentage	0.49%	0.50%
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	26,176,233	24,858,904
Non-Covered Loans, Percentage	97.63%	97.38%
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	582,572	599,986
Non-Covered Loans, Percentage	2.17%	2.35%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	54,256	69,907
Non-Covered Loans, Percentage	0.20%	0.27%
Total Other Loan Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	$ 636,828	$ 669,893
Non-Covered Loans, Percentage	2.37%	2.62%