Quantitative Information Associated With Fair Value Measurement of Level 3 Financial Instrument (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Apr. 25, 2018
Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration		$ 51,400
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Universal Robots (UR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Target achievement, volatility	12.90%
Discount Rate	3.70%
Monte Carlo Simulation | Revenue for the period July 1, 2015-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Universal Robots (UR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 11,314
Monte Carlo Simulation | Revenue for the period July 1, 2018-December 31, 2018 | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Target achievement, volatility	18.00%
Discount Rate	0.50%
Monte Carlo Simulation | Revenue for the period July 1, 2018-December 31, 2018 | Significant Unobservable Inputs (Level 3) | Mobile Industrial Robots (MiR)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 49,628