Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	$ 850	$ 3,100
FHLB Advance	0	155,000
9% Convertible Junior Subordinated Debentures	53,239	110,204
Total financial liabilities	935,279	1,146,712
Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	850	3,100
FHLB Advance	0	157,585
9% Convertible Junior Subordinated Debentures	71,597	151,000
Total financial liabilities	$ 965,547	1,251,673
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%
Senior Notes | 5.75% Senior Notes Due 2023 | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 241,419	241,255
Senior Notes | 5.75% Senior Notes Due 2023 | Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 251,009	256,213
Senior Notes | 5.25% Senior Notes Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	5.25%
Senior Notes | 5.25% Senior Notes Due 2028 | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 640,621	640,253
Senior Notes | 5.25% Senior Notes Due 2028 | Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 642,941	$ 686,875
9% Convertible Junior Subordinated Debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	9.00%