Segments and Geographical Information Segments and Geographical Information - (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	[1]	$ 1,473,413	$ 1,079,874	$ 845,486
Gross profit		1,116,947	815,294	640,110
Operating Income (Loss)		353,611	248,921	188,634
Depreciation and amortization		37,739	24,002	18,004
Clear Aligner
Segment Reporting Information [Line Items]
Revenue		1,309,262	958,327	800,186
Scanner and Services
Segment Reporting Information [Line Items]
Revenue		164,151	121,547	45,300
Clear Aligner
Segment Reporting Information [Line Items]
Gross profit		1,019,563	747,494	628,187
Operating Income (Loss)		564,648	411,817	371,113
Depreciation and amortization		21,581	13,742	9,842
Scanners And Services
Segment Reporting Information [Line Items]
Gross profit		97,384	67,800	11,923
Operating Income (Loss)		49,613	37,498	(12,337)
Depreciation and amortization		4,385	3,871	3,839
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Operating Income (Loss)		(260,650)	(200,394)	(170,142)
Depreciation and amortization		$ 11,773	$ 6,389	$ 4,323

[1] Long-lived assets are attributed to countries based on entity that owns the assets.