Segments and Geographical Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Net revenues	$ 600,697	$ 490,259	$ 1,149,668	$ 927,183
Gross profit	432,289	365,582	834,385	692,990
Income from operations	176,490	122,691	264,191	220,883
Interest income	3,465	1,917	6,098	4,093
Impairments and other charges	0	0	29,782	0
Depreciation and amortization	23,491	12,632	46,169	24,066
Other income (expense), net	13,892	(7,099)	8,146	(6,922)
Net income before provision for income taxes and equity in losses of investee	193,847	117,509	278,435	218,054
Operating segments
Segment Reporting Information [Line Items]
Income from operations	283,296	207,957	470,196	385,493
Clear Aligner
Segment Reporting Information [Line Items]
Net revenues	496,702	433,241	965,907	818,746
Gross profit	366,142	331,612	717,500	628,588
Income from operations	244,029	190,287	402,670	351,741
Impairments and other charges	0	0	29,782	0
Depreciation and amortization	11,277	6,759	22,412	13,143
Scanner
Segment Reporting Information [Line Items]
Net revenues	103,995	57,018	183,761	108,437
Gross profit	66,147	33,970	116,885	64,402
Income from operations	39,267	17,670	67,526	33,752
Impairments and other charges	0	0	0	0
Depreciation and amortization	2,451	1,169	4,548	2,273
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Income from operations	(106,806)	(85,266)	(206,005)	(164,610)
Impairments and other charges	0	0	0	0
Depreciation and amortization	$ 9,763	$ 4,704	$ 19,209	$ 8,650

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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