Fair Value Measurements - Fair Value Inputs, Quantitative Information (Details) - Rempex - Event-based milestones $ in Thousands	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Contingent purchase price	$ 18,825	$ 19,650
Measurement Input, Default Rate | Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.46	0.71
Measurement Input, Default Rate | Significant Unobservable Inputs (Level 3) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.18	0.18
Measurement Input, Default Rate | Significant Unobservable Inputs (Level 3) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.90	0.90
Measurement Input, Discount Rate | Significant Unobservable Inputs (Level 3) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.048	0.048
Measurement Input, Discount Rate | Significant Unobservable Inputs (Level 3) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.073	0.075