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 6 Months Ended
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
position
Jun. 30, 2018
USD ($)
position
Jun. 30, 2017
USD ($)
Debt Securities, Available-for-sale [Abstract]        
Other-than-temporary impairment losses $ (174) $ (429) $ (268) $ (429)
Other than Temporary Impairment Losses, Investments, Number, Available-for-sale Securities | position   1 2  
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Market Value $ 127,580   $ 127,580  
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average Cumulative Losses 6.70%      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average Three-Month Prepayment Speed 0.083      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Delinquency Rate 20.30%      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities, Weighted Average FICO Score 662      
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]        
Cumulative credit loss at beginning of period $ (6,489) $ (5,606) (6,395) (5,606)
Other-than-temporary impairments not previously recognized (85) (429) (85) (429)
Increases related to other-than-temporary impairments on securities with previously recognized other-than-temporary impairments (89) 0 (183) 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 $ (6,663) $ (6,035) $ (6,663) $ (6,035)