Stockholder's Deficit - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance, Number of shares	26,336
Granted, Number of shares	82
Exercised, Number of shares	(1,670)
Forfeited and expired, Number of shares	(302)
Balance, Number of shares	24,446	26,336
Options exercisable at March 31, 2018, Number of shares	14,583
Balance, Weighted average remaining contractual life	6 years 4 months 24 days	6 years 4 months 24 days
Options exercisable at March 31, 2018, Weighted average remaining contractual life	4 years 9 months 18 days
Granted, Weighted average grant date fair value per share	$ 19.32
Outstanding, ending balance	$ 644,801
Options exercisable, ending balance	$ 407,437
Balance, Weighted average exercise price	$ 4.59
Granted, Weighted average exercise price	45.96
Exercised, Weighted average exercise price	3.04
Forfeited and expired, Weighted average exercise price	6.37
Balance, Weighted average exercise price	4.81	$ 4.59
Options exercisable at March 31, 2018, Weighted average exercise price	$ 3.16