Loans - Composition of Loan Portfolio (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	$ 32,232,581		$ 29,821,715
Net deferred loan origination costs	19,428		16,274
Non-Covered Loans, Percentage	100.00%		100.00%
Allowance for losses on non-covered loans	(139,744)		(141,946)
Non-covered loans held for investment, net	32,112,265		29,696,043
Covered loans	2,504,622		2,788,618
Allowance for losses on covered loans	(45,682)		(64,069)
Covered loans, net	2,458,940		2,724,549
Loans held for sale	680,147		306,915
Total loans, net	35,251,352		32,727,507
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	22,862,495		20,699,927
Non-Covered Loans, Percentage	70.93%		69.41%
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	7,660,776		7,364,231
Non-Covered Loans, Percentage	23.78%		24.70%
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	404,750		560,730
Non-Covered Loans, Percentage	1.26%		1.88%
Covered loans	2,282,064
Acquisition, Development and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	310,585		344,100
Non-Covered Loans, Percentage	0.96%		1.15%
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	31,238,606		28,968,988
Non-Covered Loans, Percentage	96.92%		97.14%
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	824,186		712,260
Non-Covered Loans, Percentage	2.56%		2.39%
Lease financing, unearned income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	135,833		101,431
Non-Covered Loans, Percentage	0.42%		0.34%
Total Commercial and Industrial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	960,019	[1],[2]	813,691	[1],[3]
Non-Covered Loans, Percentage	2.98%		2.73%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	33,956		39,036
Non-Covered Loans, Percentage	0.11%		0.13%
Total Other Loan Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	$ 993,975		$ 852,727
Non-Covered Loans, Percentage	3.08%		2.86%

[1] Includes lease financing receivables, all of which were classified as “pass.”

[2] Includes lease financing receivables, all of which were current at September 30, 2014.

[3] Includes lease financing receivables, all of which were current at December 31, 2013.