Loans and Allowance for Loan Losses (Details Textual) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Mortgage Loans on Real Estate [Line Items]
Loans modified in a troubled debt restructuring	$ 75,600,000		$ 66,500,000
Principal balance of loans with payment plans	11,000,000		28,100,000
Loans and Allowance for Loan Losses (Textual) [Abstract]
Description related to classification of major category and sub categories of loans held	We evaluate the classification of our one-to four- family mortgage loans, consumer loans and other loans primarily on a pooled basis by delinquency. Loans that are past due 60 to 89 days are classified as special mention and loans that are past due 90 days or more are classified as substandard. We obtain updated valuations for one- to four- family mortgage loans by the time a loan becomes 180 days past due.
Minimum days after which loans will be classified as Special loans	60 days
Maximum days after which loans will be classified as special loans	89 days
Minimum Days after which loans will be classified as Substandard loans	90 days
Days after which loans are evaluated	180 days
Percentage of Loans within New York Metropolitan Area	81.80%		81.70%
Initial terms of interest-only loans originating as adjustable-rate mortgage loans	5, 7 or 10 years
Initial terms of interest only loans one	5 years
Initial terms of interest only loans two	7 years
Initial terms of interest only loans three	10 years
Term (in years) of interest-only loans offered as fixed-rate loans	30 years
Number of years with interest-only payments for interest-only loans offered as fixed-rate loans	10 years
Time period the Company has been originating limited documentation loans	Over 15 years
Period of loans originating as limited documentation loans	15 years
Loans eligible for limited documentation processing	ARM loans, interest-only first mortgage loans and 10-, 15-, 20-, and 30-year fixed-rate loans to owner-occupied primary and second home applicants
First Maturity of Fixed Rate Loan	10 years
Second Maturity of Fixed Rate Loan	15 years
Three Maturity of Fixed Rate Loan	20 years
Four Maturity of Fixed Rate Loan	30 years
Maximum percentage of borrowings available under limited documentation loans	65% of the lower of the appraised value or purchase price of the property
Maximum Percentage of Borrowings	65.00%
Troubled debt restructuring for which we ceased accruing interest	2,400,000
Maximum loan amount for limited documentation loans	750,000
Originated amortizing limited documentation loans	3,890,000,000		3,850,000,000
Originated limited documentation interest-only loans	955,300,000		956,200,000
Non-performing loans originated amortizing limited documentation loans	137,400,000		126,900,000
Non-performing loans originated limited documentation interest-only loans	74,600,000		71,000,000
Period in which loans are considered contractually past due	90 days or more
Number of delinquency days before new collateral values for loans are obtained	180 days
Deferral principal payments period	6 months
Interest income on non-accrual loans that would have been recognized if interest had been recorded based upon original contract terms	14,800,000
Net (charge-offs) recoveries	(18,078,000)	(21,291,000)	(82,783,000)
Loan Period	90 days
Current Dues [Member]
Mortgage Loans on Real Estate [Line Items]
Principal balance of loans with payment plans	7,700,000		19,700,000
30-59 Days past due [Member]
Mortgage Loans on Real Estate [Line Items]
Loans modified in a troubled debt restructuring	7,700,000		7,400,000
Principal balance of loans with payment plans	683,000		2,000,000
60-89 Days [Member]
Mortgage Loans on Real Estate [Line Items]
Loans modified in a troubled debt restructuring	4,900,000		4,800,000
Principal balance of loans with payment plans	1,800,000		3,100,000
90 Days or more [Member]
Mortgage Loans on Real Estate [Line Items]
Loans modified in a troubled debt restructuring	11,800,000		11,400,000
Principal balance of loans with payment plans	814,000		3,300,000
One- to four-family, Interest-only [Member]
Mortgage Loans on Real Estate [Line Items]
Total loans	4,830,000,000		4,780,000,000
Non-performing interest-only loans	$ 237,400,000		$ 213,900,000