Loans Receivable and Allowance for Loan Losses (Details 12) (Geographic concentration risk, Residential mortgage loans)	12 Months Ended
	Dec. 31, 2014
New York
Percentage of total residential mortgage loans by state or region
Percentage of total	29.60%
Connecticut
Percentage of total residential mortgage loans by state or region
Percentage of total	9.90%
Illinois
Percentage of total residential mortgage loans by state or region
Percentage of total	8.80%
Massachusetts
Percentage of total residential mortgage loans by state or region
Percentage of total	8.60%
Virginia
Percentage of total residential mortgage loans by state or region
Percentage of total	7.50%
New Jersey
Percentage of total residential mortgage loans by state or region
Percentage of total	6.90%
Maryland
Percentage of total residential mortgage loans by state or region
Percentage of total	6.40%
California
Percentage of total residential mortgage loans by state or region
Percentage of total	5.70%
Non-performing | New York
Percentage of total residential mortgage loans by state or region
Percentage of total	11.40%
Non-performing | Connecticut
Percentage of total residential mortgage loans by state or region
Percentage of total	4.50%
Non-performing | Illinois
Percentage of total residential mortgage loans by state or region
Percentage of total	14.30%
Non-performing | Massachusetts
Percentage of total residential mortgage loans by state or region
Percentage of total	4.40%
Non-performing | Virginia
Percentage of total residential mortgage loans by state or region
Percentage of total	10.30%
Non-performing | New Jersey
Percentage of total residential mortgage loans by state or region
Percentage of total	14.00%
Non-performing | Maryland
Percentage of total residential mortgage loans by state or region
Percentage of total	14.90%
Non-performing | California
Percentage of total residential mortgage loans by state or region
Percentage of total	11.90%