CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net income (loss)	$ (95,049)	$ (27,161)
Less: Income (loss) from discontinued operations, net of tax	0	889
Income (loss) from continuing operations	(95,049)	(26,272)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization of property, equipment and software	52,149	57,163
Amortization of acquired intangible assets	6,466	11,583
Stock-based compensation	35,644	41,141
Impairments of Investments	10,044	0
Deferred income taxes	(6,575)	759
(Gain) loss from changes in fair value of investments	8,068	1,145
Amortization of debt discount on convertible senior notes	5,806	5,242
Change in assets and liabilities, net of acquisitions and dispositions:
Accounts receivable	27,296	16,229
Prepaid expenses and other current assets	1,489	(11,139)
Accounts payable	(9,340)	(10,723)
Accrued merchant and supplier payables	(172,982)	(182,954)
Accrued expenses and other current liabilities	51,140	(41,491)
Other, net	10,272	(18,159)
Net cash provided by (used in) operating activities from continuing operations	(75,572)	(157,476)
Net cash provided by (used in) operating activities from discontinued operations	0	(2,195)
Net cash provided by (used in) operating activities	(75,572)	(159,671)
Investing activities
Purchases of property and equipment and capitalized software	(37,517)	(29,461)
Proceeds from maturity of investment	0	1,843
Acquisition of business, net of acquired cash	(57,821)	0
Acquisitions of intangible assets and other investing activities	(758)	(184)
Net cash provided by (used in) investing activities from continuing operations	(96,096)	(27,802)
Net cash provided by (used in) investing activities from discontinued operations	0	(9,548)
Net cash provided by (used in) investing activities	(96,096)	(37,350)
Financing activities
Payments for purchases of treasury stock	0	(51,513)
Taxes paid related to net share settlements of stock-based compensation awards	(16,138)	(15,356)
Proceeds from stock option exercises and employee stock purchase plan	2,504	2,477
Distributions to noncontrolling interest holders	(6,940)	(6,426)
Payments of capital lease obligations	(17,239)	(16,670)
Payments of contingent consideration related to acquisitions	(1,815)	(5,689)
Other financing activities	0	(473)
Net cash provided by (used in) financing activities	(39,628)	(93,650)
Effect of exchange rate changes on cash, cash equivalents and restricted cash, including cash classified within current assets of discontinued operations	(6,644)	17,297
Net increase (decrease) in cash, cash equivalents and restricted cash, including cash classified within current assets of discontinued operations	(217,940)	(273,374)
Less: Net increase (decrease) in cash classified within current assets of discontinued operations	0	(28,866)
Net increase (decrease) in cash, cash equivalents and restricted cash	(217,940)	(244,508)
Cash, cash equivalents and restricted cash, beginning of period	885,481	874,906
Cash, cash equivalents and restricted cash, end of period	667,541	630,398
Non-cash investing and financing activities
Equipment acquired under capital lease obligations	9,581	16,509
Leasehold improvements funded by lessor	557	402
Liability for purchases of treasury stock	0	561
Increase (decrease) in liabilities related to purchases of property and equipment and capitalized software	(789)	(539)
Investments acquired in connection with business dispositions	0	2,022
Contingent consideration liability incurred in connection with acquisition of business	1,589	0
Financing obligation incurred in connection with acquisition of business	$ 8,604	$ 0