Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale	$ 1,433,626	$ 1,184,202
Principal payment received	128,809	129,139	$ 121,890
Equity securities	80,735	78,385
Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired bank loan participations held for investment	6,949	0
Significant Unobservable Inputs Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal payment received	456
Significant Unobservable Inputs Level 3 | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired bank loan participations held for investment	6,949	0
Commercial mortgage and asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale	252,457	197,025
Commercial mortgage and asset-backed | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale	252,457	197,025
Commercial mortgage and asset-backed | Significant Unobservable Inputs Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, available-for-sale		4,228	$ 4,700
Equity securities | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	80,735	78,385
Equity securities | Significant Unobservable Inputs Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	$ 43	$ 214