Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale securities
Amortized cost, fixed maturities	$ 708,282
Amortized cost	708,282	$ 754,636
Gross unrealized gains	3,522	7,722
Gross unrealized losses	7,609	3,645
Estimated fair value, fixed maturities	704,195
Estimated fair value	704,195	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	36,799	11,873
Gross unrealized gains, fixed maturities	0	0
Gross unrealized losses, fixed maturities	374	139
Estimated fair value, fixed maturities	36,425	11,734
States & political subdivisions
Available-for-sale securities
Amortized cost, fixed maturities	257,612	254,533
Gross unrealized gains, fixed maturities	2,392	5,351
Gross unrealized losses, fixed maturities	3,139	620
Estimated fair value, fixed maturities	256,865	259,264
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	279,814	346,759
Gross unrealized gains, fixed maturities	1,031	1,688
Gross unrealized losses, fixed maturities	3,176	1,924
Estimated fair value, fixed maturities	277,669	346,523
Residential mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	2,524	25,324
Gross unrealized gains, fixed maturities	0	371
Gross unrealized losses, fixed maturities	30	124
Estimated fair value, fixed maturities	2,494	25,571
Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost, fixed maturities	47,491	33,475
Gross unrealized gains, fixed maturities	12	26
Gross unrealized losses, fixed maturities	643	697
Estimated fair value, fixed maturities	46,860	32,804
Collateralized debt obligations
Available-for-sale securities
Amortized cost, fixed maturities	65,421	57,838
Gross unrealized gains, fixed maturities	80	237
Gross unrealized losses, fixed maturities	207	41
Estimated fair value, fixed maturities	65,294	58,034
Other debt securities
Available-for-sale securities
Amortized cost, fixed maturities	18,621	11,496
Gross unrealized gains, fixed maturities	7	32
Gross unrealized losses, fixed maturities	40	0
Estimated fair value, fixed maturities	$ 18,588	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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