Fair Value Measurements - Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets:
Fixed maturity securities	$ 121,996	$ 136,536
Equity securities	5,645	5,627
Short-term investments	9,905	11,427
Total marketable investments measured at fair value	137,546	153,590
Investments measured at NAV	4,187	4,060
Total marketable investments measured at fair value	141,733	157,650
Liabilities:
Debt		29,888
Total Liabilities measured at fair value	31,907	29,888
U.S. Government
Assets:
Fixed maturity securities	15,503	17,090
State and local government
Assets:
Fixed maturity securities	15,756	17,503
Corporate debt
Assets:
Fixed maturity securities	31,122	38,908
Asset-backed securities
Assets:
Fixed maturity securities	23,841	23,540
Mortgage-backed securities
Assets:
Fixed maturity securities	29,805	33,458
Commercial mortgage-backed securities
Assets:
Fixed maturity securities	3,790	3,491
Collateralized mortgage obligations
Assets:
Fixed maturity securities	2,179	2,546
Senior Unsecured Notes
Liabilities:
Debt	22,000
Subordinated Notes
Liabilities:
Debt	9,907
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Fixed maturity securities	0	0
Equity securities	5,381	5,381
Short-term investments	9,905	8,429
Total marketable investments measured at fair value	15,286	13,810
Liabilities:
Debt		0
Total Liabilities measured at fair value	22,000	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. Government
Assets:
Fixed maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| State and local government
Assets:
Fixed maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate debt
Assets:
Fixed maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Asset-backed securities
Assets:
Fixed maturity securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Mortgage-backed securities
Assets:
Fixed maturity securities	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Commercial mortgage-backed securities
Assets:
Fixed maturity securities	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Collateralized mortgage obligations
Assets:
Fixed maturity securities	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Senior Unsecured Notes
Liabilities:
Debt	22,000
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Subordinated Notes
Liabilities:
Debt	0
Significant Other Observable Inputs (Level 2)
Assets:
Fixed maturity securities	121,996	136,536
Equity securities	264	246
Short-term investments	0	2,998
Total marketable investments measured at fair value	122,260	139,780
Liabilities:
Debt		0
Total Liabilities measured at fair value		0
Significant Other Observable Inputs (Level 2) \| U.S. Government
Assets:
Fixed maturity securities	15,503	17,090
Significant Other Observable Inputs (Level 2) \| State and local government
Assets:
Fixed maturity securities	15,756	17,503
Significant Other Observable Inputs (Level 2) \| Corporate debt
Assets:
Fixed maturity securities	31,122	38,908
Significant Other Observable Inputs (Level 2) \| Asset-backed securities
Assets:
Fixed maturity securities	23,841	23,540
Significant Other Observable Inputs (Level 2) \| Mortgage-backed securities
Assets:
Fixed maturity securities	29,805	33,458
Significant Other Observable Inputs (Level 2) \| Commercial mortgage-backed securities
Assets:
Fixed maturity securities	3,790	3,491
Significant Other Observable Inputs (Level 2) \| Collateralized mortgage obligations
Assets:
Fixed maturity securities	2,179	2,546
Significant Unobservable Inputs (Level 3)
Assets:
Fixed maturity securities		0
Equity securities	0	0
Short-term investments	0	0
Total marketable investments measured at fair value		0
Liabilities:
Debt		29,888
Total Liabilities measured at fair value	9,907	29,888
Significant Unobservable Inputs (Level 3) \| U.S. Government
Assets:
Fixed maturity securities	0	0
Significant Unobservable Inputs (Level 3) \| State and local government
Assets:
Fixed maturity securities	0	0
Significant Unobservable Inputs (Level 3) \| Corporate debt
Assets:
Fixed maturity securities	0	0
Significant Unobservable Inputs (Level 3) \| Asset-backed securities
Assets:
Fixed maturity securities		0
Significant Unobservable Inputs (Level 3) \| Senior Unsecured Notes
Liabilities:
Debt	0
Significant Unobservable Inputs (Level 3) \| Subordinated Notes
Liabilities:
Debt	9,907
Partnership interest
Assets:
Investments measured at NAV	$ 4,187	$ 4,060

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

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