Stock Plans and Share-Based Compensation - Summary of Stock Option Activity (Details) - Stock Options shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Outstanding beginning of period (in shares) | shares	4,582
Granted (in shares) | shares	10,462
Forfeited (in shares) | shares	(10,860)
Exercised (in shares) | shares	22
Outstanding end of period (in shares) | shares	4,163
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 24.57
Granted (in dollars per share) | $ / shares	49.63
Forfeited (in dollars per share) | $ / shares	46.81
Exercised (in dollars per share) | $ / shares	25.18
Outstanding at end of period (in dollars per share) | $ / shares	$ 29.52
Exercisable (in shares) | shares	0
Exercisable (in dollars per share) | $ / shares	$ 0.00