Share Repurchase Program (Tables)

3 Months Ended

Mar. 31, 2018

Proceeds from (Repurchase of) Equity [Abstract]

Schedule of shares repurchased

	For the Three Months Ended   March 31,
	2018		2017
Shares repurchased	2,188		1,829
Average price per share	$	251.08	$	268.09
Total investment	$	549,428	$	490,312