Share Repurchase Program (Tables)

9 Months Ended

Sep. 30, 2018

Proceeds from (Repurchase of) Equity [Abstract]

Schedule of shares repurchased

	For the Three Months Ended   September 30,				For the Nine Months Ended   September 30,
	2018		2017		2018		2017
Shares repurchased	932		2,743		4,695		8,047
Average price per share	$	306.22	$	200.70	$	266.48	$	235.26
Total investment	$	285,183	$	550,530	$	1,251,013	$	1,893,068