Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
		Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss		$ (35,792)	$ (24,221)	$ (133,119)
Less: Income (loss) from discontinued operations		(1,345)	(1,751)	(6,365)
Loss from continuing operations		(34,447)	(22,470)	(126,754)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation, Depletion and Amortization			86,355	87,585
Amortization of acquired intangible assets		4,400	17,622	13,643
Share-based Compensation			60,318	92,360
Restructuring Costs and Asset Impairment Charges			0	45
Gain (Loss) on Disposition of Business		(2,060)	0	(11,399)
Gain (Loss) on Disposition of Intangible Assets		0	(17,149)	0
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments		0	(7,624)	0
Deferred income taxes			845	(6,468)
Gain from changes in fair value of contingent consideration	[1]	(162)	48	4,130
Fair Value, Option, Changes in Fair Value, Gain (Loss)		1,594	5,100	7,301
Amortization of Debt Discount (Premium)		2,458	7,964	4,854
Change in assets and liabilities, net of acquisitions:
Restricted cash			2,637	(332)
Accounts receivable			787	(2,460)
Prepaid expenses and other current assets			(3,114)	8,295
Accounts payable			(5,616)	(2,610)
Accrued merchant and supplier payables			(197,836)	(168,944)
Accrued expenses and other current liabilities			(39,396)	(48,323)
Other, net			(21,538)	(16,588)
Net cash provided by (used in) operating activities from continuing operations			(133,067)	(165,665)
Net cash used in operating activities from discontinued operations			(2,195)	(5,892)
Net cash provided by (used in) operating activities			(135,262)	(171,557)
Investing activities
Purchases of property and equipment and capitalized software			(43,716)	(49,033)
Cash Divested from Deconsolidation			0	(1,128)
Proceeds from Sale of Intangible Assets			18,333	0
Proceeds from Sale, Maturity and Collection of Investments			16,561	1,685
Payments to Acquire Businesses, Net of Cash Acquired			0	(940)
Acquisitions of intangible assets and other investing activities			(750)	(2,121)
Net cash used in investing activities from continuing operations			(9,572)	(51,537)
Net cash used in investing activities from discontinued operations			(9,548)	(182)
Net cash used in investing activities			(19,120)	(51,719)
Financing activities
Proceeds from Issuance of Senior Long-term Debt			0	250,000
Payments of Debt Issuance Costs			0	(8,097)
Purchase of Convertible Note Hedges			0	(59,163)
Proceeds from Issuance of Warrants			0	35,495
Payments for purchases of treasury stock			(61,233)	(115,619)
Taxes paid related to net share settlements of stock-based compensation awards			(23,340)	(23,327)
Proceeds from stock option exercises and employee stock purchase plan			5,486	4,976
Partnership distribution payments to noncontrolling interest holders			(8,974)	(9,151)
Payment of Contingent Consideration			(7,790)	(285)
Payments of capital lease obligations			(25,298)	(21,961)
Proceeds from (Payments for) Other Financing Activities			(473)	0
Net cash used in financing activities			(121,622)	52,868
Effect of exchange rate changes on cash and cash equivalents			22,818	6,793
Net decrease in cash and cash equivalents, including cash classified within current assets held for sale			(253,186)	(163,615)
Less: Increase in cash and cash equivalents classified within current assets held for sale			(28,866)	(1,388)
Net decrease in cash and cash equivalents			(224,320)	(162,227)
Cash and cash equivalents, beginning of period			862,977	824,307
Cash and cash equivalents, end of period		662,080	638,657	662,080
Non-cash investing and financing activities
Equipment acquired under capital lease obligations			17,892	17,556
Payments for Tenant Improvements			402	4,990
Liability for Purchases of Treasury Stock			0	1,041
Accounts payable and accrued expenses related to purchases of property and equipment and capitalized software			(396)	(2,250)
Continuing Operations [Member]
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Share-based Compensation		25,800	60,300	92,400
Discontinued Operations [Member]
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Amortization of acquired intangible assets		0	0	0
Share-based Compensation		700	200	2,400
Investment Type [Member]
Non-cash investing and financing activities
Noncash or Part Noncash Acquisition, Investments Acquired			2,022	11,050
GroupMax [Member]
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ 3,900	$ 3,600	$ 8,200

[1] Changes in the fair value of contingent consideration liabilities are classified within "Acquisition-related expense (benefit), net" on the condensed consolidated statements of operations.