Goodwill and Intangible Assets, Net - Components of Intangible Assets with Definite Lives (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Cost	$ 2,436,088	$ 2,285,209
Accumulated Amortization	(1,606,281)	(1,295,629)
Net	829,807	989,580
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Cost	665,027	622,117
Accumulated Amortization	(304,130)	(185,468)
Net	360,897	436,649
Supplier relationships
Finite-Lived Intangible Assets [Line Items]
Cost	655,467	618,543
Accumulated Amortization	(367,609)	(289,834)
Net	287,858	328,709
Technology
Finite-Lived Intangible Assets [Line Items]
Cost	531,735	480,823
Accumulated Amortization	(440,852)	(355,471)
Net	90,883	125,352
Domain names
Finite-Lived Intangible Assets [Line Items]
Cost	131,944	117,109
Accumulated Amortization	(70,203)	(53,607)
Net	61,741	63,502
Other
Finite-Lived Intangible Assets [Line Items]
Cost	451,915	446,617
Accumulated Amortization	(423,487)	(411,249)
Net	$ 28,428	$ 35,368

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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