Stock-based Compensation (Summary of Stock Option Activity) (Details) - $ / shares	9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period, Shares	1,396,152	[1]	1,619,948
Granted, Shares	460,610	[1]	524,940
Exercised, Shares	(327,205)	[1]	(564,389)
Forfeited or cancelled, Shares	(28,042)	[1]	(207,203)
Outstanding, end of period, Shares	1,501,515	[1]	1,373,296
Outstanding, beginning of period, Weighted Average Exercise Price	$ 68.63		$ 56.57
Granted, Weighted Average Exercise Price	90.85		82.74
Exercised, Weighted Average Exercise Price	57.29		48.80
Forfeited or cancelled, Weighted Average Exercise Price	79.40		68.23
Outstanding, end of period, Weighted Average Exercise Price	$ 77.72		$ 68.01
Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding shares that are not expected to vest	298,899

[1] Included in outstanding shares at the end of the period were 298,899 shares that are not expected to vest due to the announcement of the pending resignation of the Company’s CEO.