Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available-for-sale securities
Amortized cost, fixed maturities	$ 708,895
Amortized cost	708,895	$ 754,636
Gross unrealized gains	4,594	7,722
Gross unrealized losses	8,061	3,645
Estimated fair value, fixed maturities	705,428
Estimated fair value	705,428	758,713
Fixed maturities
Available-for-sale securities
Amortized cost, fixed maturities		741,799
Gross unrealized gains, fixed maturities		7,707
Gross unrealized losses, fixed maturities		3,545
Estimated fair value, fixed maturities		745,961
U.S. treasury
Available-for-sale securities
Amortized cost, fixed maturities	36,769	11,873
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	327	139
Estimated fair value, fixed maturities	36,442	11,734
States & political subdivisions
Available-for-sale securities
Amortized cost, fixed maturities	257,498	254,533
Gross unrealized gains, fixed maturities	3,443	5,351
Gross unrealized losses, fixed maturities	2,450	620
Estimated fair value, fixed maturities	258,491	259,264
Foreign government securities
Available-for-sale securities
Amortized cost, fixed maturities	500	501
Gross unrealized gains, fixed maturities	0	2
Gross unrealized losses, fixed maturities	1	0
Estimated fair value, fixed maturities	499	503
Corporate debt securities
Available-for-sale securities
Amortized cost, fixed maturities	285,639	346,759
Gross unrealized gains, fixed maturities	663	1,688
Gross unrealized losses, fixed maturities	4,296	1,924
Estimated fair value, fixed maturities	282,006	346,523
Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	21,739	25,324
Gross unrealized gains, fixed maturities	374	371
Gross unrealized losses, fixed maturities	244	124
Estimated fair value, fixed maturities	21,869	25,571
Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	32,878	33,475
Gross unrealized gains, fixed maturities	5	26
Gross unrealized losses, fixed maturities	607	697
Estimated fair value, fixed maturities	32,276	32,804
Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	71,009	57,838
Gross unrealized gains, fixed maturities	103	237
Gross unrealized losses, fixed maturities	136	41
Estimated fair value, fixed maturities	70,976	58,034
Other debt securities
Available-for-sale securities
Amortized cost, fixed maturities	2,863	11,496
Gross unrealized gains, fixed maturities	6	32
Gross unrealized losses, fixed maturities	0	0
Estimated fair value, fixed maturities	$ 2,869	11,528
Nonredeemable preferred stock \| Financial services sector
Available-for-sale securities
Amortized cost, equity securities		11,719
Gross unrealized gains, equity securities		15
Gross unrealized losses, equity securities		75
Estimated fair value, equity securities		11,659
Nonredeemable preferred stock \| Utilities sector
Available-for-sale securities
Amortized cost, equity securities		1,118
Gross unrealized gains, equity securities		0
Gross unrealized losses, equity securities		25
Estimated fair value, equity securities		$ 1,093

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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