Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Share Based Compensation [Abstract]

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

	Three Months Ended
	March 31,
	2016		2015
Stock options	$	201	$	185
Nonvested stock awards and restricted stock units		848		752
Employee stock purchase plan		23		18
Non-elective and elective 401(k) matching contribution in stock		689		699
Director stock ownership plan		37		31
Total stock-based compensation expense	$	1,798	$	1,685

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

					Weighted
			Weighted		Average
			Average		Remaining	Aggregate
		Number of	Exercise Price		Contractual	Intrinsic
		Options	(per option)		Term (years)	Value
Options outstanding at December 31, 2015		99,671	$	71.73
	Options granted	67,444		72.12
Options outstanding at March 31, 2016		167,115	$	71.89	5.7	$	2,317
Options expected to vest at March 31, 2016		103,040	$	75.82	6.4	$	1,027
Options exercisable at March 31, 2016		64,075	$	65.57	4.4	$	1,290

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

						Weighted
						Average	Weighted			Weighted
					Number	Remaining	Average		Number	Average
Range of					of Options	Contractual	Exercise Price		of Options	Exercise Price
Exercise Prices					Outstanding	Term (years)	(per option)		Exercisable	(per option)
$	—	-	$	10.00	—	—	$	—	—	$	—
$	10.01	-	$	20.00	2,367	0.8		18.82	2,367		18.82
$	20.01	-	$	30.00	—	—		—	—		—
$	30.01	-	$	40.00	6,317	2.9		38.13	6,317		38.13
$	40.01	-	$	50.00	—	—		—	—		—
$	50.01	-	$	60.00	21,055	3.9		58.26	21,055		58.26
$	60.01	-	$	70.00	—	—		—	—		—
$	70.01	-	$	80.00	101,230	6.2		72.57	22,281		73.47
$	80.01	-	$	90.00	36,146	5.9		87.30	12,055		87.30
					167,115	5.7		71.89	64,075		65.57

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	2016
Number of options granted	67,444
Dividend yield	1.49	%
Expected volatility	28.39	%
Risk-free interest rate	1.08	%
Expected term (years)	4.0

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

			Weighted
			Average Grant
		Number of	Date Fair Value
		Shares	(per share)
Nonvested awards, December 31, 2015		113,910	$	72.91
	Granted	23,661	$	72.22
	Vested	(17,785)	$	58.97
Nonvested awards, March 31, 2016		119,786	$	74.84

			Weighted
			Average Grant
		Number of	Date Fair Value
		Units	(per unit)
Nonvested awards, December 31, 2015		6,174	$	74.14
	Granted	1,841	$	72.12
	Vested	(1,418)	$	58.26
Nonvested awards, March 31, 2016		6,597	$	76.99