Reserves for Insurance Claims and Claim Expenses - Narrative (Details)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
loan
claim
Sep. 30, 2016
USD ($)
loan
Sep. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]          
IBNR, default period (at least)   60 days      
Liability for insurance claims $ 2,133 $ 2,133 $ 358 $ 679 $ 83
Primary loans in default | loan 115 115      
Number of claims paid | claim 3        
Claims paid $ 93 $ 0 0    
Claims applied to deductible   165      
Favorable prior year development   214 $ 79    
Reserve for prior year insurance claims and claim expenses $ 240 $ 240      
Fannie Mae          
Liability for Claims and Claims Adjustment Expense [Line Items]          
Number of loans in pool past due 60 days or more | loan 46 46      
Risk in Force of loans in pool past due 60 days or more $ 3,200 $ 3,200      
Deductible on policy   $ 10,200      
Loan-to-value ratio (less than)   0.8