Stock-based Compensation - Schedule of Stock Option Activity (Details) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Awards (in millions)
Beginning Balance | shares	9.6
Grants in period | shares	0.9
Exercises in period | shares	(1.2)
Forfeitures in period | shares	(0.1)
Ending Balance | shares	9.2
Weighted Average Exercise Price (usd per share)
Beginning Balance | $ / shares	$ 14.40
Grants in period (usd per share) | $ / shares	29.52
Exercised (usd per share) | $ / shares	10.54
Forfeited (usd per share) | $ / shares	28.10
Ending Balance | $ / shares	$ 16.23
Vested and Expected to Vest
Vested and expected to vest, in shares | shares	9.2
Vested and expected to vest, weighted average exercise price (usd) | $ / shares	$ 16.23
Vested and expected to vest, aggregate intrinsic value | $	$ 145.1
Vested and expected to vest, weighted average contractual life (in years)	6 years 10 months 27 days
Exercisable
Exercisable, in shares | shares	7.2
Exercisable, usd per share | $ / shares	$ 13.15
Exercisable, aggregate intrinsic value | $	$ 136.5
Exercisable, weighted average contractual life (in years)	6 years 4 months 13 days