Investments (Schedule of amortized cost and estimated fair value of investment securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Cost or Amortized Cost	$ 275,066	$ 264,006
Gross Unrealized Gains	21,552	21,924
Gross Unrealized Losses	(5,226)	(1,611)
Fair Value	291,392	284,319
Fixed income securities [Member]
Cost or Amortized Cost	244,577	234,978
Gross Unrealized Gains	908	2,738
Gross Unrealized Losses	(3,898)	(958)
Fair Value	241,587	236,758
Fixed income securities [Member] | U.S. Government and agencies [Member]
Cost or Amortized Cost	15,383	9,531
Gross Unrealized Gains	115	175
Gross Unrealized Losses	(211)	(57)
Fair Value	15,287	9,649
Fixed income securities [Member] | Obligations of states and political subdivisions [Member]
Cost or Amortized Cost	57,231	81,741
Gross Unrealized Gains	452	1,171
Gross Unrealized Losses	(721)	(317)
Fair Value	56,962	82,595
Fixed income securities [Member] | Corporate securities [Member]
Cost or Amortized Cost	93,444	88,474
Gross Unrealized Gains	306	1,197
Gross Unrealized Losses	(1,600)	(220)
Fair Value	92,150	89,451
Fixed income securities [Member] | Residential mortgage-backed securities [Member]
Cost or Amortized Cost	41,651	28,557
Gross Unrealized Gains	34	124
Gross Unrealized Losses	(844)	(157)
Fair Value	40,841	28,524
Fixed income securities [Member] | Commercial mortgage-backed securities [Member]
Cost or Amortized Cost	14,906	11,228
Gross Unrealized Gains		61
Gross Unrealized Losses	(324)	(119)
Fair Value	14,582	11,170
Fixed income securities [Member] | Asset backed securities [Member]
Cost or Amortized Cost	21,962	15,447
Gross Unrealized Gains	1	10
Gross Unrealized Losses	(198)	(88)
Fair Value	21,765	15,369
Equity Securities [Member]
Cost or Amortized Cost	30,489	29,028
Gross Unrealized Gains	20,644	19,186
Gross Unrealized Losses	(1,328)	(653)
Fair Value	49,805	47,561
Equity Securities [Member] | Basic materials [Member]
Cost or Amortized Cost	1,159	768
Gross Unrealized Gains	118	124
Gross Unrealized Losses	(14)
Fair Value	1,263	892
Equity Securities [Member] | Communications [Member]
Cost or Amortized Cost	3,097	3,027
Gross Unrealized Gains	1,828	1,449
Gross Unrealized Losses	(144)	(154)
Fair Value	4,781	4,322
Equity Securities [Member] | Consumer, cyclical [Member]
Cost or Amortized Cost	5,234	5,303
Gross Unrealized Gains	3,977	4,156
Gross Unrealized Losses	(62)	(120)
Fair Value	9,149	9,339
Equity Securities [Member] | Consumer, non-cyclical [Member]
Cost or Amortized Cost	6,802	7,090
Gross Unrealized Gains	4,978	3,940
Gross Unrealized Losses	(425)	(125)
Fair Value	11,355	10,905
Equity Securities [Member] | Energy [Member]
Cost or Amortized Cost	2,047	2,003
Gross Unrealized Gains	326	272
Gross Unrealized Losses	(319)	(44)
Fair Value	2,054	2,231
Equity Securities [Member] | Financial [Member]
Cost or Amortized Cost	3,038	2,007
Gross Unrealized Gains	296	410
Gross Unrealized Losses	(120)
Fair Value	3,214	2,417
Equity Securities [Member] | Industrial [Member]
Cost or Amortized Cost	5,000	5,038
Gross Unrealized Gains	3,528	4,167
Gross Unrealized Losses	(118)
Fair Value	8,410	9,205
Equity Securities [Member] | Technology [Member]
Cost or Amortized Cost	4,112	3,792
Gross Unrealized Gains	5,593	4,668
Gross Unrealized Losses	(126)	(210)
Fair Value	$ 9,579	$ 8,250