Loans Receivable and Allowance for Loan Losses (Details 8) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 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	$ 386,040		$ 346,906
Loans collectively evaluated for impairment	12,097,457		12,809,008
Total loans	12,483,497		13,155,914
Loans individually evaluated for impairment, allowance for loan losses	24,766		5,046
Loans collectively evaluated for impairment, allowance for loan losses	118,234		140,455
Total allowance for loan losses	143,000	143,900	145,501	148,472	148,102	157,185
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	12,239,352		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	313,495		272,146
Loans collectively evaluated for impairment	7,985,023		9,439,080
Total loans	8,298,518		9,711,226
Loans individually evaluated for impairment, allowance for loan losses	22,265		1,001
Loans collectively evaluated for impairment, allowance for loan losses	61,159		88,266
Total allowance for loan losses	83,424	78,788	89,267	90,764	87,394	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	55,391		56,116
Loans collectively evaluated for impairment	3,062,623		2,350,562
Total loans	3,118,014		2,406,678
Loans individually evaluated for impairment, allowance for loan losses	2,179		2,576
Loans collectively evaluated for impairment, allowance for loan losses	36,066		32,938
Total allowance for loan losses	38,245	40,865	35,514	40,863	48,142	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	17,154		18,644
Loans collectively evaluated for impairment	805,666		755,272
Total loans	822,820		773,916
Loans individually evaluated for impairment, allowance for loan losses	322		1,469
Loans collectively evaluated for impairment, allowance for loan losses	13,682		12,935
Total allowance for loan losses	14,004	16,642	14,404	11,558	9,109	11,972
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	244,145		264,094
Total loans	244,145		264,094
Loans collectively evaluated for impairment, allowance for loan losses	7,327		6,316
Total allowance for loan losses	$ 7,327	$ 7,605	$ 6,316	$ 5,287	$ 3,457	$ 3,800