Performance-Based Common Stock Warrants - Narrative (Details) - Performance-based warrants	Mar. 09, 2016 USD ($) vesting_period $ / shares shares	Dec. 31, 2017 shares
Class of Warrant or Right [Line Items]
Number of shares called by warrants (in shares) (up to) | shares	725,000
Exercise price of warrants (in dollars per share) | $ / shares	$ 54.55
Number of vesting periods | vesting_period	3
Term of successive vesting periods (in years)	2 years
Vesting period one (in years)	2 years
Total vesting period (in years)	6 years
Warrants vested | shares		175,000
Supply Commitment
Class of Warrant or Right [Line Items]
Supply threshold level one, amount | $	$ 260,000,000
Supply threshold level three, amount | $	340,000,000
Supply threshold, amount | $	$ 1,020,000,000.00
Maximum potential warrants that will vest (in shares) | shares	250,000