Investments Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	$ 434,905	$ 355,668
Estimated Fair Value, 12 Months or More	36,967	83,198
Estimated Fair Value, Total	471,872	438,866
Unrealized Losses
Unrealized Losses, Less than 12 Months	9,269	8,836
Unrealized Losses, 12 Months or More	4,000	9,941
Unrealized Losses, Total	13,269	18,777
Subtotal, fixed maturity securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	428,541	336,259
Estimated Fair Value, 12 Months or More	22,126	71,144
Estimated Fair Value, Total	450,667	407,403
Unrealized Losses
Unrealized Losses, Less than 12 Months	8,954	7,097
Unrealized Losses, 12 Months or More	1,580	5,845
Unrealized Losses, Total	10,534	12,942
U.S. Treasury securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	301	1,801
Estimated Fair Value, Total	301	1,801
Unrealized Losses
Unrealized Losses, Less than 12 Months		4
Unrealized Losses, Total		4
Obligations of states and political subdivisions
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	79,960	34,837
Estimated Fair Value, 12 Months or More		4,777
Estimated Fair Value, Total	79,960	39,614
Unrealized Losses
Unrealized Losses, Less than 12 Months	3,912	342
Unrealized Losses, 12 Months or More		84
Unrealized Losses, Total	3,912	426
Residential mortgage-backed securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	182,265	85,561
Estimated Fair Value, 12 Months or More	4,595	32,845
Estimated Fair Value, Total	186,860	118,406
Unrealized Losses
Unrealized Losses, Less than 12 Months	2,476	860
Unrealized Losses, 12 Months or More	180	768
Unrealized Losses, Total	2,656	1,628
Commercial mortgage-backed securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	15,521	26,113
Estimated Fair Value, Total	15,521	26,113
Unrealized Losses
Unrealized Losses, Less than 12 Months	432	218
Unrealized Losses, Total	432	218
Other asset-backed securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	31,869	14,454
Estimated Fair Value, Total	31,869	14,454
Unrealized Losses
Unrealized Losses, Less than 12 Months	90	145
Unrealized Losses, Total	90	145
Corporate and other securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	118,625	173,493
Estimated Fair Value, 12 Months or More	17,531	33,522
Estimated Fair Value, Total	136,156	207,015
Unrealized Losses
Unrealized Losses, Less than 12 Months	2,044	5,528
Unrealized Losses, 12 Months or More	1,400	4,993
Unrealized Losses, Total	3,444	10,521
Equity securities
Estimated Fair Value
Estimated Fair Value, Less than 12 Months	6,364	19,409
Estimated Fair Value, 12 Months or More	14,841	12,054
Estimated Fair Value, Total	21,205	31,463
Unrealized Losses
Unrealized Losses, Less than 12 Months	315	1,739
Unrealized Losses, 12 Months or More	2,420	4,096
Unrealized Losses, Total	$ 2,735	$ 5,835