Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total fixed maturity securities, available-for-sale	$ 1,570,605	$ 1,433,626
Equity securities	71,394	80,735
Recurring basis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	1,000		$ 177	$ 214
Nonrecurring basis
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired bank loan participations held for investment		6,949
Nonrecurring basis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired bank loan participations held for investment		6,949
Common stock | Recurring basis
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	10,533	17,988
Common stock | Recurring basis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity securities	$ 4	$ 43
Market approach | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total fixed maturity securities, available-for-sale				$ 4,200