Fair Value Measurements - Fair Value Inputs, Quantitative Information (Details) - Rempex - Event-based milestones $ in Thousands	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Contingent purchase price	$ 18,822	$ 19,650
Probabilities of successes | Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.46	0.71
Probabilities of successes | Significant Unobservable Inputs (Level 3) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.18	0.18
Probabilities of successes | Significant Unobservable Inputs (Level 3) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.75	0.90
Discount rate | Significant Unobservable Inputs (Level 3) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Measurement inputs	0.050	0.048
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