Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

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

During the nine months ended September 30, 2018, the Company made the following awards of restricted stock:

Date	Shares Granted	Plan	Grant Date Fair Value Per Share		Vesting Period
2/15/2018	39,950	2005 Employee Stock Plan	$	71.75	Ratably over 5 years from grant date
2/27/2018	1,150	2005 Employee Stock Plan	$	72.60	Ratably over 5 years from grant date
5/15/2018	530	2005 Employee Stock Plan	$	74.00	Ratably over 5 years from grant date
5/22/2018	6,000	2018 Non-Employee Director Stock Plan	$	76.58	Shares vested immediately

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

The Company has made the following awards of nonqualified options to purchase shares of common stock during the nine months ended September 30, 2018:

	Nine Months Ended September 30, 2018
Date of grant	4/3/2018
Plan	2010 Non-Employee Director Stock Plan
Options granted	5,000
Vesting period (1)	21 months
Expiration date	4/3/2028
Expected volatility	21.15		%
Expected life (years)	5.5
Expected dividend yield	1.94		%
Risk free interest rate	2.62		%
Fair value per option	$	13.46

(1)    Vesting period began on the grant date.