Long-term Debt - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Senior debentures
Debt Instrument [Line Items]
Long-term debt, gross	$ 185,000	$ 185,000	$ 85,000
Senior debentures \| 2030 senior debentures
Debt Instrument [Line Items]
Long-term debt, gross	100,000	$ 100,000	0
Earliest redemption date		Jun. 15, 2025
Redemption price (percent)		100.00%
Maturity date		Jun. 15, 2030
Senior debentures \| 2022 senior debentures
Debt Instrument [Line Items]
Long-term debt, gross	50,000	$ 50,000	50,000
Earliest redemption date		Aug. 14, 2020
Redemption price (percent)		100.00%
Maturity date		Feb. 14, 2022
Senior debentures \| 2027 senior debentures
Debt Instrument [Line Items]
Long-term debt, gross	35,000	$ 35,000	35,000
Earliest redemption date		Aug. 14, 2025
Redemption price (percent)		100.00%
Maturity date		Feb. 14, 2027
Subordinated debentures
Debt Instrument [Line Items]
Long-term debt, gross	111,250	$ 111,250	111,250
Subordinated debentures \| 2026 subordinated debentures
Debt Instrument [Line Items]
Long-term debt, gross	$ 15,000	15,000	0
Earliest redemption date	Sep. 01, 2021
Redemption price (percent)	100.00%
Maturity date	Sep. 01, 2026
Subordinated debentures \| 2025 subordinated debentures
Debt Instrument [Line Items]
Long-term debt, gross	$ 11,250	$ 11,250	$ 11,250
Earliest redemption date		Nov. 30, 2020
Maturity date		Nov. 30, 2025

Earliest date before maturity when the issuer can call the outstanding debt instrument for repayment or conversion to equity, in CCYY-MM-DD format.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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