Stock-Based Compensation (Stock Option Activity) (Details) - Stock Options $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Shares
Options, outstanding, beginning of period (in shares) | shares	701,134
Options, granted (in shares) | shares	887,030
Options, exercised (in shares) | shares	(64,916)
Options, expired (in shares) | shares	(58,217)
Options, forfeited (in shares) | shares	(171,847)
Options, outstanding, end of period (in shares) | shares	1,293,184
Options, vested and expected to vest (in shares) | shares	1,111,610
Options, exercisable (in shares) | shares	456,308
Weighted Average Exercise Price
Weighted average exercise price, beginning of period (per share) | $ / shares	$ 80.04
Weighted average exercise price, granted (per share) | $ / shares	48.35
Weighted average exercise price, exercised (per share) | $ / shares	40.59
Weighted average exercise price, expired (per share) | $ / shares	84.43
Weighted average exercise price, forfeited (per share) | $ / shares	65.82
Weighted average exercise price, end of period (per share) | $ / shares	61.98
Weighted average exercise price, vested and expected to vest (per share) | $ / shares	64.50
Weighted average exercise price, exercisable (per share) | $ / shares	$ 81.35
Weighted average remaining contractual term (in years)	7 years 4 months 3 days
Weighted average remaining contractual term, vested and expected to vest (in years)	6 years 11 months 14 days
Weighted average remaining contractual term, exercisable (in years)	3 years 3 months 16 days
Options, outstanding, intrinsic value | $	$ 0.9
Options, vested and expected to vest, intrinsic value | $	0.6
Options, vested and expected to vest, exercisable | $	$ 0.0