Change in Carrying Value of Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2015	$ 79,162
Balance as of September 30, 2016	82,987
Clear Aligner
Goodwill [Roll Forward]
Balance as of December 31, 2015	61,074
Adjustments	121	[1]
Balance as of September 30, 2016	$ 61,195

[1] The adjustments to goodwill during the nine months ended September 30, 2016 were due to foreign currency translation.