Loans Receivable and Allowance for Loan Losses - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Sep. 30, 2010	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 12, 2014	Jul. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans					$ 11,111,727	$ 11,909,722
Loans receivable					11,153,081	11,957,448
Charge-offs					8,270	29,589	$ 37,040
Credit to the provision for loan losses					12,072	9,469	(19,601)
Accrued interest receivable					34,996	36,628
Non-performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans, interest that would have been recognized					5,400	5,600	15,600
Actual payment recorded as interest income					3,400	3,600	$ 6,200
Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans					10,859,034	11,660,354
Loans in process of foreclosure collateralized by residential real estate property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable					51,000	24,700
Total loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable					$ 27,600	29,900
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortizing hybrid ARM fixed rate period one					5 years		3 years
Amortizing hybrid ARM fixed rate period two					7 years
Amortizing hybrid ARM fixed rate period three					10 years
Amortizing hybrid adjustable rate mortgage, period after initial fixed rate				1 year	1 year
Amortizing interest-only hybrid ARM fixed rate period two, prior to the 2010 fourth quarter				5 years
Amortizing interest-only hybrid ARM fixed rate period three, prior to the 2010 fourth quarter				7 years
Interest-only hybrid ARM loans, interest-only payment term					10 years
Residential | Minimum | Geographic concentration risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total residential loans					5.00%
Residential | Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans					$ 6,015,415	6,873,536
Charge-offs					6,149	19,868	$ 26,644
Credit to the provision for loan losses					(1,520)	23,464	$ (9,368)
Residential | Pre 2007 interest only loans | Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans					388,000	1,060,000
Residential | Reduced documentation loans | Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans					885,200	1,020,000
Residential | Reduced documentation loans | Mortgage Loans | SISA (stated income, stated asset) loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans					$ 135,700	$ 148,900
Residential | Non-performing loans held-for-sale, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			$ 8,700
Non performing residential mortgage loans transferred to held for sale		$ 195,000	195,000
Non performing residential mortgage loans held for sale		186,300	$ 186,300
Credit to the provision for loan losses		$ 5,700
Carrying value, loans sold								$ 4,000	$ 173,700
Loss on sales of loans, net	$ 920