Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	$ 3,100	$ 3,100
FHLB Advance	155,000	155,000
5.75% Senior Notes	421,443	420,867
9% Convertible Junior Subordinated Debentures	256,872	256,872
Total financial liabilities	833,315	832,739
Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	3,100	3,100
FHLB Advance	161,773	156,422
5.75% Senior Notes	441,545	471,827
9% Convertible Junior Subordinated Debentures	305,562	346,289
Total financial liabilities	$ 908,880	$ 974,538
Senior Notes | 5.75% Senior Notes Due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	5.75%
9% Convertible Junior Subordinated Debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	9.00%