Investments (Details 3) $ in Thousands	Mar. 31, 2017 USD ($) Holdings	Dec. 31, 2016 USD ($) Holdings
Fair value
Less than 12 months	$ 234,976	$ 269,475
12 months or longer	17,755	22,193
Total	252,731	291,668
Unrealized losses
Less than 12 months	3,336	4,116
12 months or longer	738	1,047
Total	$ 4,074	$ 5,163
No. of holdings | Holdings	232	253
Investment grade
Fair value
Less than 12 months	$ 219,190	$ 239,041
12 months or longer	14,437	16,061
Total	233,627	255,102
Unrealized losses
Less than 12 months	2,993	3,605
12 months or longer	539	399
Total	$ 3,532	$ 4,004
No. of holdings | Holdings	180	136
Non-investment grade
Fair value
Less than 12 months	$ 9,794	$ 24,484
12 months or longer	3,318	6,132
Total	13,112	30,616
Unrealized losses
Less than 12 months	183	309
12 months or longer	199	648
Total	$ 382	$ 957
No. of holdings | Holdings	51	116
Fixed maturities
Fair value
Less than 12 months	$ 228,984	$ 263,525
12 months or longer	17,755	22,193
Total	246,739	285,718
Unrealized losses
Less than 12 months	3,176	3,914
12 months or longer	738	1,047
Total	$ 3,914	$ 4,961
No. of holdings | Holdings	231	252
U.S. treasury
Fair value
Less than 12 months	$ 5,038	$ 5,031
12 months or longer	0	0
Total	5,038	5,031
Unrealized losses
Less than 12 months	49	62
12 months or longer	0	0
Total	$ 49	$ 62
No. of holdings | Holdings	1	1
States & political subdivisions
Fair value
Less than 12 months	$ 52,740	$ 84,611
12 months or longer	0	0
Total	52,740	84,611
Unrealized losses
Less than 12 months	1,723	2,293
12 months or longer	0	0
Total	$ 1,723	$ 2,293
No. of holdings | Holdings	22	40
Corporate debt securities
Fair value
Less than 12 months	$ 114,334	$ 112,453
12 months or longer	9,337	8,692
Total	123,671	121,145
Unrealized losses
Less than 12 months	780	987
12 months or longer	222	399
Total	$ 1,002	$ 1,386
No. of holdings | Holdings	159	155
Residential mortgage-backed securities
Fair value
Less than 12 months	$ 6,555	$ 7,451
12 months or longer	4,621	4,974
Total	11,176	12,425
Unrealized losses
Less than 12 months	57	60
12 months or longer	120	131
Total	$ 177	$ 191
No. of holdings | Holdings	11	13
Commercial mortgage-backed securities
Fair value
Less than 12 months	$ 28,986	$ 26,509
12 months or longer	2,692	4,319
Total	31,678	30,828
Unrealized losses
Less than 12 months	496	437
12 months or longer	385	496
Total	$ 881	$ 933
No. of holdings | Holdings	28	28
Collateralized debt obligations
Fair value
Less than 12 months	$ 21,331	$ 27,470
12 months or longer	1,105	4,208
Total	22,436	31,678
Unrealized losses
Less than 12 months	71	75
12 months or longer	11	21
Total	$ 82	$ 96
No. of holdings | Holdings	10	15
Common stock
Fair value
Less than 12 months	$ 5,992	$ 5,950
12 months or longer	0	0
Total	5,992	5,950
Unrealized losses
Less than 12 months	160	202
12 months or longer	0	0
Total	$ 160	$ 202
No. of holdings | Holdings	1	1