Composition of Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	$ 28,038,251	$ 27,273,707
Net deferred loan origination costs	13,091	10,757
Non-Covered Loans, Percentage	100.00%	100.00%
Allowance for losses on non-covered loans	(140,689)	(140,948)	(137,914)	(137,290)
Non-covered loans held for investment, net	27,910,653	27,143,516
Covered loans	3,032,172	3,284,061
Allowance for losses on covered loans	(60,431)	(51,311)	(51,771)	(33,323)
Total covered loans, net	2,971,741	3,232,750
Loans held for sale	756,601	1,204,370
Total loans, net	31,638,995	31,580,636
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	19,218,540	18,595,833
Non-Covered Loans, Percentage	68.54%	68.18%
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	7,310,119	7,436,598
Non-Covered Loans, Percentage	26.07%	27.27%
Acquisition, Development and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	417,948	397,917
Non-Covered Loans, Percentage	1.49%	1.46%
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	375,585	203,435
Non-Covered Loans, Percentage	1.35%	0.75%
Covered loans	2,753,300
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	27,322,192	26,633,783
Non-Covered Loans, Percentage	97.45%	97.66%
Allowance for losses on non-covered loans	(123,915)	(127,934)	(124,294)	(121,995)
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	671,074	590,044
Non-Covered Loans, Percentage	2.39%	2.16%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	44,985	49,880
Non-Covered Loans, Percentage	0.16%	0.18%
Total Other Loan Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	$ 716,059	$ 639,924
Non-Covered Loans, Percentage	2.55%	2.34%