Intangible Assets and Asset Acquisition Obligations - Remaining minimum royalty payments (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Intangible Assets and Asset Acquisition Obligations
2018	$ 67,500
2019	135,000
2020	135,000
2021	135,000
Total remaining minimum royalty payments due	472,500
Less: Unamortized discount	(43,229)
Carrying value of minimum royalty payments	$ 429,271