Stock-Based Compensation (Stock Option Activity) (Details) - Stock Options $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, outstanding, beginning of period (in shares) | shares	504,462
Options, granted (in shares) | shares	255,825
Options, exercised (in shares) | shares	(36,005)
Options, outstanding, end of period (in shares) | shares	724,282
Options, vested and expected to vest (in shares) | shares	659,693
Options, exercisable (in shares) | shares	355,330
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, beginning of period (per share) | $ / shares	$ 69.99
Weighted average exercise price, granted (per share) | $ / shares	90.90
Weighted average exercise price, exercised (per share) | $ / shares	24.43
Weighted average exercise price, end of period (per share) | $ / shares	79.64
Weighted average exercise price, vested and expected to vest (per share) | $ / shares	78.24
Weighted average exercise price, exercisable (per share) | $ / shares	$ 64.44
Weighted average remaining contractual term (in years)	7 years 10 months 10 days
Weighted average remaining contractual term, vested and expected to vest (in years)	7 years 8 months 7 days
Weighted average remaining contractual term, exercisable (in years)	6 years 1 month 18 days
Options, outstanding, intrinsic value | $	$ 12.1
Options, vested and expected to vest, intrinsic value | $	11.9
Options, vested and expected to vest, exercisable | $	$ 11.0