Stock Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Stock Compensation

Schedule of valuation assumptions used for valuation of fair value of stock compensation granted

	Employee Stock Options						Employee Stock Purchase Plan
	For the year ended December 31,						For the year ended December 31,
	2020		2019		2018		2020		2019		2018
Average risk-free interest rates	0.80	%	2.27	%	2.61	%	0.17	%	1.82	%	2.62	%
Average expected life (in years)	4.98		5.27		5.26		0.50		0.50		0.50
Volatility	40	%	45	%	45	%	45	%	31	%	46	%
Weighted-average fair value (in dollars)	32.65		32.38		34.20		19.13		14.04		15.80