Stock-based Compensation (Summary of Stock Option Plan Activity) (Details) - $ / shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Stock-based Compensation [Abstract]
Outstanding, beginning of period, Shares	1,619,948	2,236,620
Granted, Shares	524,940	659,850
Exercised, Shares	(495,242)	(204,444)
Forfeited or cancelled, Shares	(161,207)	(90,137)
Outstanding, end of period, Shares	1,488,439	2,601,889
Outstanding, beginning of period, Weighted Average Exercise Price	$ 56.57	$ 46.61
Granted, Weighted Average Exercise Price	82.74	70.28
Exercised, Weighted Average Exercise Price	48.57	44.29
Forfeited or cancelled, Weighted Average Exercise Price	66.80	51.52
Outstanding, end of period, Weighted Average Exercise Price	$ 67.36	$ 52.63