Loans Receivable and Allowance for Loan Losses (Details 8) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	$ 406,232	$ 346,906
Loans collectively evaluated for impairment	12,441,473	12,809,008
Total loans	12,847,705	13,155,914
Loans individually evaluated for impairment, allowance for loan losses	25,941	5,046
Loans collectively evaluated for impairment, allowance for loan losses	118,309	140,455
Total allowance for loan losses	144,250	145,501	149,899	157,185
Consumer and Other Loans
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans collectively evaluated for impairment	259,005	264,094
Total loans	259,005	264,094
Loans collectively evaluated for impairment, allowance for loan losses	6,357	6,316
Total allowance for loan losses	6,357	6,316	3,672	3,800
Mortgage Loans (Gross)
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Total loans	12,588,700	12,891,820
Mortgage Loans (Gross) | Residential
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	336,427	272,146
Loans collectively evaluated for impairment	8,860,886	9,439,080
Total loans	9,197,313	9,711,226
Loans individually evaluated for impairment, allowance for loan losses	24,484	1,001
Loans collectively evaluated for impairment, allowance for loan losses	67,062	88,266
Total allowance for loan losses	91,546	89,267	90,898	105,991
Mortgage Loans (Gross) | Multi-Family
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	50,917	56,116
Loans collectively evaluated for impairment	2,525,401	2,350,562
Total loans	2,576,318	2,406,678
Loans individually evaluated for impairment, allowance for loan losses	1,157	2,576
Loans collectively evaluated for impairment, allowance for loan losses	32,795	32,938
Total allowance for loan losses	33,952	35,514	44,927	35,422
Mortgage Loans (Gross) | Commercial Real Estate
Balances of our loans receivable and the related allowance for loan loss allocation by segment and by the impairment methodology followed in determining the allowance for loan losses
Loans individually evaluated for impairment	18,888	18,644
Loans collectively evaluated for impairment	796,181	755,272
Total loans	815,069	773,916
Loans individually evaluated for impairment, allowance for loan losses	300	1,469
Loans collectively evaluated for impairment, allowance for loan losses	12,095	12,935
Total allowance for loan losses	$ 12,395	$ 14,404	$ 10,402	$ 11,972