Fair Value of Financial Instruments - Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Debt	$ 685,078	$ 686,006
Senior Notes | 7.625% Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Debt	96,950	96,928
Senior Notes | 7.625% Notes | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value estimates of debt	83,880	103,560
Senior Notes | 6.75% Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Debt	347,252	347,091
Senior Notes | 6.75% Notes | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value estimates of debt	361,628	371,366
Surplus Notes | Subordinated Debentures
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Debt	72,168	72,168
Surplus Notes | Subordinated Debentures | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value estimates of debt	72,118	72,103
Line of Credit | 2019 Credit Agreement
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Debt	140,000	140,000
Line of Credit | 2019 Credit Agreement | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value estimates of debt	$ 141,227	$ 148,272