Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

A summary of our stock option activity, and related information for the year ended December 31, 2017 is as follows (in millions except weighted-average exercise price and weighted-average remaining contractual term):



	Number of Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding at December 31, 2016	0.7		$	7.40
Exercised	(0.3	)	8.21
Forfeited	—		—
Outstanding at December 31, 2017	0.4		$	6.71	1.30	$	19.5
Exercisable at December 31, 2017	0.4		$	6.71	1.30	$	19.5

Schedule of Intrinsic Value of Options Exercised and Fair Value of Options Vested

The total intrinsic value of options exercised as of the date of exercise was as follows (in millions):



	Years Ended December 31,
	2017		2016		2015
Intrinsic value of options exercised	$	21.6	$	39.9	$	125.8

Schedule of Share-Based Compensation Expenses

The following table summarizes share-based compensation expense related to employee stock options, restricted stock units and employee stock purchases for the years ended December 31, 2017, 2016 and 2015 (in millions):



	Years Ended December 31,
	2017		2016		2015
Cost of sales	$	9.6	$	12.0	$	8.1
Research and development	37.5		39.8		28.5
Selling, general and administrative	59.1		59.0		46.1
Share-based compensation expense included in net loss	$	106.2	$	110.8	$	82.7

Schedule of Valuation Assumptions for Employee Stock Purchase Plan

ESPP:



	Years Ended December 31,
	2017		2016		2015
Risk free interest rate	0.75 – 1.12		0.46 – 0.57		0.15 – 0.25
Dividend yield	—	%	—	%	—	%
Expected volatility of the Company’s stock	0.33 – 0.56		0.33 – 0.57		0.30 – 0.44
Expected life (in years)	1		1		1

Schedule of Restricted Stock Units Activity

The following table sets forth a summary of our RSU activity as of and for the year ended December 31, 2017 (in millions except weighted average grant date fair value):



	Shares		Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value
Nonvested at December 31, 2016	3.7		$	62.51
Granted	1.3		75.78
Vested	(1.9	)	58.92
Forfeited	(0.4	)	67.97
Nonvested at December 31, 2017	2.7		$	70.68	$	154.5

Schedule of Stock Options Reserved for Future Issuance

Reserved Shares

We have reserved shares of common stock for future issuance as follows (in millions):



	December 31,
	2017	2016
Stock options and awards under our plans:
Stock options granted and outstanding	0.4	0.7
Unvested restricted stock units	2.7	3.7
Reserved for future grant	4.7	2.0
Employee Stock Purchase Plan	1.3	1.4
Total	9.1	7.8