Fair Value Measurements - Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 13	$ 4,539	$ 4,959
Transfers out of Level 3		(3,100)
Total realized/unrealized gains (losses) [Abstract]
Included in earnings and reported as net realized investment gains		3,663
Included in earnings and reported as losses incurred, net	0	0	0
Acquisitions	0	0	0
Sales	(13)	(5,089)	(420)
Balance at end of period	0	13	4,539
Total fixed income securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	13	271	691
Transfers out of Level 3		0
Total realized/unrealized gains (losses) [Abstract]
Included in earnings and reported as net realized investment gains		0
Included in earnings and reported as losses incurred, net	0	0	0
Acquisitions	0	0	0
Sales	(13)	(258)	(420)
Balance at end of period	0	13	271
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	0	4,268	4,268
Transfers out of Level 3		(3,100)
Total realized/unrealized gains (losses) [Abstract]
Included in earnings and reported as net realized investment gains		3,663
Included in earnings and reported as losses incurred, net	0	0	0
Acquisitions	0	0	0
Sales	0	(4,831)	0
Balance at end of period	0	0	4,268
Real Estate Acquired
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	14,535	12,713	11,748
Total realized/unrealized gains (losses) [Abstract]
Included in earnings and reported as losses incurred, net	(476)	(1,995)	(1,315)
Acquisitions	24,204	33,912	34,749
Sales	(31,011)	(30,095)	(32,469)
Balance at end of period	$ 7,252	$ 14,535	$ 12,713