Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale securities
Amortized cost, fixed maturities	$ 741,799
Amortized cost	754,636	$ 708,555
Gross unrealized gains	7,722	9,899
Gross unrealized losses	3,645	5,163
Estimated fair value, fixed maturities	745,961
Estimated fair value	758,713	713,291
Fixed maturities
Available-for-sale securities
Amortized cost, fixed maturities	741,799	702,403
Gross unrealized gains, fixed maturities	7,707	9,899
Gross unrealized losses, fixed maturities	3,545	4,961
Estimated fair value, fixed maturities	745,961	707,341
U.S. treasury
Available-for-sale securities
Amortized cost, fixed maturities	11,873	5,093
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	139	62
Estimated fair value, fixed maturities	11,734	5,031
Government sponsored entities
Available-for-sale securities
Amortized cost, fixed maturities		2,004
Gross unrealized gains, fixed maturities		22
Gross unrealized losses, fixed maturities		0
Estimated fair value, fixed maturities		2,026
States & political subdivisions
Available-for-sale securities
Amortized cost, fixed maturities	254,533	249,312
Gross unrealized gains, fixed maturities	5,351	6,113
Gross unrealized losses, fixed maturities	620	2,293
Estimated fair value, fixed maturities	259,264	253,132
Foreign government securities
Available-for-sale securities
Amortized cost, fixed maturities	501
Gross unrealized gains, fixed maturities	2
Gross unrealized losses, fixed maturities	0
Estimated fair value, fixed maturities	503
Corporate debt securities
Available-for-sale securities
Amortized cost, fixed maturities	346,759	321,041
Gross unrealized gains, fixed maturities	1,688	3,293
Gross unrealized losses, fixed maturities	1,924	1,386
Estimated fair value, fixed maturities	346,523	322,948
Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	25,324	16,232
Gross unrealized gains, fixed maturities	371	61
Gross unrealized losses, fixed maturities	124	191
Estimated fair value, fixed maturities	25,571	16,102
Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	33,475	37,723
Gross unrealized gains, fixed maturities	26	59
Gross unrealized losses, fixed maturities	697	933
Estimated fair value, fixed maturities	32,804	36,849
Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	57,838	68,998
Gross unrealized gains, fixed maturities	237	351
Gross unrealized losses, fixed maturities	41	96
Estimated fair value, fixed maturities	58,034	69,253
Other debt securities
Available-for-sale securities
Amortized cost, fixed maturities	11,496	2,000
Gross unrealized gains, fixed maturities	32	0
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	11,528	2,000
Nonredeemable preferred stock
Available-for-sale securities
Amortized cost, equity securities	12,837
Gross unrealized gains, equity securities	15
Gross unrealized losses, equity securities	100
Estimated fair value, equity securities	$ 12,752
Common stock
Available-for-sale securities
Amortized cost, equity securities		6,152
Gross unrealized gains, equity securities		0
Gross unrealized losses, equity securities		202
Estimated fair value, equity securities		$ 5,950

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