Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]

During the nine months ended September 30, 2019, the Company made the following awards of restricted stock:

Date	Shares Granted	Plan	Grant Date Fair Value Per Share		Vesting Period
2/21/2019	43,250	2005 Employee Stock Plan	$	83.87	Ratably over 5 years from grant date
3/15/2019	600	2005 Employee Stock Plan	$	79.55	Ratably over 5 years from grant date
4/1/2019	1,090	2005 Employee Stock Plan	$	82.62	Ratably over 3 years from grant date
5/21/2019	6,500	2018 Non-Employee Director Stock Plan	$	77.08	Shares vested immediately

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

The Company did not grant any awards of options to purchase shares of common stock during the nine months ended September 30, 2019.