Fair Value Measurements - Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 4,959	$ 4,083
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	0	0
Purchases	0	3,091
Sales	(8)	(2,561)
Balance at end of period	4,959	4,083	$ 4,951	$ 4,613
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	691	1,228
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	0	0
Purchases	0	0
Sales	(8)	(36)
Balance at end of period	691	1,228	683	1,192
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	4,268	2,855
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	0	0
Purchases	0	3,091
Sales	0	(2,525)
Balance at end of period	4,268	2,855	4,268	3,421
Real Estate Acquired
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	11,748	12,149
Total realized/unrealized gains (losses):
Included in earnings and reported as losses incurred, net	(163)	(293)
Purchases	8,683	12,267
Sales	(9,538)	(11,274)
Balance at end of period	$ 11,748	$ 12,149	$ 10,730	$ 12,849