Investments, Amortized Cost, Estimated Fair Value and Gross Unrealized Gains and Losses of Debt and Equity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Amortized cost	$ 338,660	$ 281,021
Gross unrealized gains	4,341	3,609
Gross unrealized losses	1,086	531
Estimated fair value	341,915	284,099
Available-for-sale Equity Securities, Amortized Cost Basis [Abstract]
Amortized cost	33,605	29,908
Gross unrealized gains	6,391	9,836
Gross unrealized losses	1,910	497
Estimated fair value	38,086	39,247
Held-to-maturity Securities [Abstract]
Amortized cost	6,387	7,417
Gross unrealized gains	76	73
Gross unrealized losses	190	231
Estimated fair value	6,273	7,259
United States Government Obligations and Authorities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Amortized cost	64,876	61,376
Gross unrealized gains	1,233	1,022
Gross unrealized losses	115	75
Estimated fair value	65,994	62,323
Held-to-maturity Securities [Abstract]
Amortized cost	4,221	4,490
Obligations of States and Political Subdivisions [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Amortized cost	107,211	90,728
Gross unrealized gains	1,428	956
Gross unrealized losses	42	70
Estimated fair value	108,597	91,614
Corporate [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Amortized cost	154,469	117,778
Gross unrealized gains	1,625	1,578
Gross unrealized losses	770	332
Estimated fair value	155,324	119,024
Held-to-maturity Securities [Abstract]
Amortized cost	2,101	2,681
International [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Amortized cost	12,104	11,139
Gross unrealized gains	55	53
Gross unrealized losses	159	54
Estimated fair value	12,000	11,138
Held-to-maturity Securities [Abstract]
Amortized cost	65	246
United States Government Obligations and Authorities [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	4,221	4,490
Gross unrealized gains	51	41
Gross unrealized losses	184	225
Estimated fair value	4,088	4,306
Corporate [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	2,101	2,681
Gross unrealized gains	25	31
Gross unrealized losses	6	5
Estimated fair value	2,120	2,707
International [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	65	246
Gross unrealized gains	0	1
Gross unrealized losses	0	1
Estimated fair value	$ 65	$ 246