Components of Intangible Assets and Their Estimated Useful Lives at Acquisition Date (Detail) - Mobile Industrial Robots (MiR) - USD ($) $ in Thousands		9 Months Ended
	Apr. 25, 2018	Sep. 30, 2018
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 80,670	$ 80,700
Total intangible assets, estimated useful life, years	7 years 2 months 12 days
Developed technology
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 58,900
Total intangible assets, estimated useful life, years	7 years
Trademarks and tradenames
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 13,240
Total intangible assets, estimated useful life, years	11 years
Customer Relationships
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 8,500
Total intangible assets, estimated useful life, years	2 years 6 months
Customer backlog
Business Acquisition [Line Items]
Total intangible assets, fair value	$ 30
Total intangible assets, estimated useful life, years	2 months 12 days