Acquisitions - Additional Information (Detail) - USD ($)			3 Months Ended		5 Months Ended	9 Months Ended
	Apr. 25, 2018	Feb. 26, 2018	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Revenues			$ 6,500,000		$ 11,100,000
Income (loss) before income taxes			(3,800,000)		(5,400,000)
Goodwill			392,998,000		392,998,000	$ 392,998,000		$ 252,011,000
Mobile Industrial Robots (MiR)
Business Acquisition [Line Items]
Total preliminary purchase price	$ 196,630,000
Cash paid to acquire outstanding common and preferred stock	145,200,000
Contingent consideration	51,400,000
Arrangement range of outcomes value high			$ 118,900,000		$ 118,900,000	118,900,000
Goodwill, not deductible for tax purposes	134,700,000
Net income				$ 100,339,000		306,768,000	$ 351,626,000
Goodwill	$ 134,737,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 2 months 12 days
Mobile Industrial Robots (MiR) | Fair Value Adjustment to Inventory
Business Acquisition [Line Items]
Net income						400,000	2,900,000
Mobile Industrial Robots (MiR) | Acquisition Related Costs
Business Acquisition [Line Items]
Net income						$ 2,900,000	$ 400,000
Energid Technologies Corporation
Business Acquisition [Line Items]
Total preliminary purchase price		$ 27,600,000
Goodwill		14,400,000
Acquired value of intangible assets		$ 12,300,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		7 years 8 months 12 days
Net tangible assets		$ 1,000,000