Quarterly report pursuant to Section 13 or 15(d)

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

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Available-for-Sale Securities, at Fair Value Other than Temporary Impairment, Credit Losses Recognized in Earnings (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
position
Sep. 30, 2018
USD ($)
position
Sep. 30, 2017
USD ($)
Debt Securities, Available-for-sale [Abstract]        
Other-than-temporary impairment losses $ (95) $ 0 $ (363) $ (429)
Other than Temporary Impairment Losses, Investments, Number, Available-for-sale Securities | position   1 3  
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Market Value $ 140,300   $ 140,300  
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average Cumulative Losses 8.30%      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average Three-Month Prepayment Speed 0.070      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Delinquency Rate 19.00%      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average FICO Score 668      
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]        
Cumulative credit loss at beginning of period $ (6,663) $ (6,035) (6,395) (5,606)
Other-than-temporary impairments not previously recognized (72) 0 (157) (429)
Increases related to other-than-temporary impairments on securities with previously recognized other-than-temporary impairments (23) 0 (206) 0
Decreases related to other-than-temporary impairments on securities paid down 0 0 0 0
Decreases related to other-than-temporary impairments on securities sold 0 0 0 0
Cumulative credit loss at end of period $ (6,758) $ (6,035) $ (6,758) $ (6,035)