Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of investment portfolio fair value pricing services or index price	94.10%	90.70%
Net investment losses included in net income related to financial assets	$ 1,067	$ 484
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of invested assets in total investment portfolio Level 3 recurring	4.80%
Net investment gain (loss)	$ (12,600)	$ 7,500