Segments and Geographical Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net revenues	$ 607,341	$ 505,289	$ 1,757,009	$ 1,432,472
Gross profit	437,554	371,781	1,271,939	1,064,771
Income from operations	127,152	125,208	391,343	346,091
Interest income	3,478	2,234	9,576	6,327
Impairments and other (gains) charges	(6,792)	0	22,990	0
Depreciation and amortization	19,706	14,119	57,194	38,185
Other income (expense), net	(2,211)	(837)	5,935	(7,759)
Net income before provision for income taxes and equity in losses of investee	128,419	126,605	406,854	344,659
Operating segments
Segment Reporting Information [Line Items]
Income from operations	244,712	214,165	714,908	599,658
Clear Aligner
Segment Reporting Information [Line Items]
Net revenues	516,265	427,087	1,482,172	1,245,833
Gross profit	379,202	321,772	1,096,702	950,360
Income from operations	211,952	182,667	614,622	534,408
Impairments and other (gains) charges	(6,792)	0	22,990	0
Depreciation and amortization	9,306	7,218	27,851	20,361
Scanner
Segment Reporting Information [Line Items]
Net revenues	91,076	78,202	274,837	186,639
Gross profit	58,352	50,009	175,237	114,411
Income from operations	32,760	31,498	100,286	65,250
Impairments and other (gains) charges	0	0	0	0
Depreciation and amortization	1,987	1,237	5,349	3,510
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Income from operations	(117,560)	(88,957)	(323,565)	(253,567)
Impairments and other (gains) charges	0	0	0	0
Depreciation and amortization	$ 8,413	$ 5,664	$ 23,994	$ 14,314

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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