Goodwill, In-Process Research and Development and Intellectual Property - Additional Information (Detail) - USD ($)		3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 21, 2015	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017
Goodwill And Intangible Assets [Line Items]
Goodwill			$ 70,813,000	$ 71,368,000
Accumulated impairment of goodwill			61,800,000	61,800,000
Goodwill impairment		$ 0	$ 0	$ 0
In-Process Research and Development [Member]
Goodwill And Intangible Assets [Line Items]
Discount rate	45.00%
Intellectual Property [Member]
Goodwill And Intangible Assets [Line Items]
Discount rate	45.00%
Technology and Patents Purchased [Member]
Goodwill And Intangible Assets [Line Items]
Weighted average remaining useful life			8 years 9 months 18 days	9 years 3 months 18 days
Developed Technology [Member]
Goodwill And Intangible Assets [Line Items]
Weighted average remaining useful life			4 years 3 months 18 days	4 years 9 months 18 days
Safe Stitch Medical Inc [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill			$ 93,800,000
Senhance Surgical Robotic System Acquisition [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill			$ 38,300,000
Intellectual property	$ 48,500,000
Senhance Surgical Robotic System Acquisition [Member] | In-Process Research and Development [Member]
Goodwill And Intangible Assets [Line Items]
In-process research and development	$ 17,100,000
Senhance Surgical Robotic System Acquisition [Member] | Technology and Patents Purchased [Member]
Goodwill And Intangible Assets [Line Items]
Acquisition price				$ 400,000