Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Valuation Assumptions

Weighted-average grant-date fair values of stock options and the assumptions used in estimating the fair values are as follows:

	Year Ended December 31,
	2018			2017			2016
Weighted-average grant-date fair value per share	$	26.67		$	20.11		$	10.31
Expected term (years)	5.5			5.4			5.2
Risk-free interest rate	2.30		%	2.00		%	1.67		%
Expected volatility	59.41		%	60.31		%	61.41		%

Summary of Stock Option Activity Rollforward

The following table summarizes our stock option activity from continuing operations:

	December 31, 2018
	Number of Shares		Weighted-average Exercise Price		Aggregate Intrinsic Value		Weighted- average Remaining Contractual Term
Outstanding at beginning of year	1.22		$	32.64
Granted	0.19		48.98
Exercised	(0.41	)	25.18
Forfeited / Cancelled	(0.21	)	40.31
Outstanding at end of year	0.79		$	38.46	$	22.3	5.3 years
Vested and expected to vest at end of year	0.78		$	38.39	$	8.3	5.3 years
Exercisable at end of year	0.35		$	45.22	$	22.1	4.3 years

Schedule of Unvested Restricted Stock and RSU Rollforward

The following table summarizes our unvested restricted stock and RSUs activity from continuing operations:

	December 31, 2018
	Number of Shares		Weighted-Average Grant-Date Fair Value
Unvested at beginning of year	0.31		$	28.54
Granted	0.17		51.99
Forfeited	(0.07	)	38.41
Vested	(0.14	)	27.47
Unvested at end of year	0.27		$	41.01

Schedule of Performace Units Unvested Shares Activity Rollforward

The following table, which is stated at a 100% earned percentage, summarizes our performance units activity from continuing operations:

	December 31, 2018
	Number of Shares		Weighted-Average Grant-Date Fair Value
Unvested at beginning of year	0.05		$	25.71
Granted	0.02		49.38
Forfeited	(0.03	)	36.88
Unvested at end of year	0.04		$	27.49