Acquisition of Senhance Surgical Robotic System - Schedule of Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 21, 2015
Business Acquisition [Line Items]
Goodwill	$ 71,368	$ 68,697	$ 130,869
Senhance Surgical Robotic System Acquisition [Member]
Business Acquisition [Line Items]
Accounts receivable				$ 78
Inventories				2,800
Current deferred tax asset				526
Other current assets				4,180
Property and equipment				1,384
Intellectual property				48,500
In-process research and development				17,100
Goodwill	$ 38,300			38,348
Total assets acquired				112,916
Accounts payable and other liabilities				1,915
Long-term deferred tax liabilities				18,424
Net assets acquired				$ 92,577