Loans Receivable and Allowance for Loan Losses - Schedule of Concentration Greater Than 5% of Total Mortgage Loans (Details) - Geographic concentration risk - Residential	12 Months Ended
	Dec. 31, 2016
New York
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	30.80%
Connecticut
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	9.50%
Massachusetts
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	8.30%
Virginia
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	7.60%
New Jersey
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	7.60%
Illinois
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	7.50%
Maryland
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	6.60%
California
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	5.30%
Non-performing | New York
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	10.10%
Non-performing | Connecticut
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	13.10%
Non-performing | Massachusetts
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	4.10%
Non-performing | Virginia
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	9.60%
Non-performing | New Jersey
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	18.50%
Non-performing | Illinois
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	13.70%
Non-performing | Maryland
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	16.40%
Non-performing | California
Percentage of total residential mortgage loans by state or region
Percent of Total Residential Loans	6.30%