Annual report pursuant to Section 13 and 15(d)

Available-for-Sale Securities, at Fair Value Other than Temporary Impairment, Credit Losses Recognized in Earnings (Details)

v3.8.0.1
Available-for-Sale Securities, at Fair Value Other than Temporary Impairment, Credit Losses Recognized in Earnings (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2017
USD ($)
position
Dec. 31, 2016
USD ($)
position
Dec. 31, 2015
USD ($)
Available-for-sale Securities [Abstract]                      
Other-than-temporary impairment losses $ (360) $ 0 $ (429) $ 0 $ 0 $ (1,015) $ (90) $ (717) $ (789) $ (1,822) $ (535)
Other than Temporary Impairment Losses, Investments, Number, Available-for-sale Securities | position                 2 4  
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Market Value $ 117,475               $ 117,475    
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average Cumulative Losses 5.50%                    
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average Three-Month Prepayment Speed 0.061                    
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Delinquency Rate 22.30%                    
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average FICO Score 658                    
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]                      
Cumulative credit loss at beginning of period       $ (5,606)       $ (6,499) (5,606) $ (6,499) (8,241)
Other-than-temporary impairments not previously recognized                 (429) (1,307) (238)
Increases related to other-than-temporary impairments on securities with previously recognized other-than-temporary impairments                 (360) (515) (297)
Decreases related to other-than-temporary impairments on securities paid down                 0 1,387 0
Decreases related to other-than-temporary impairments on securities sold                 0 1,328 2,277
Cumulative credit loss at end of period $ (6,395)       $ (5,606)       $ (6,395) $ (5,606) $ (6,499)