Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities
Net income (loss)	$ (51,031)	$ (297,762)	$ (413,386)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	55,801	32,055	12,952
Stock-based compensation	104,117	93,590	36,168
Deferred income taxes	(7,651)	32,203	(7,349)
Excess tax benefit on stock based compensation	(27,023)	(10,178)	(32)
Loss on equity method investees	9,925	26,652	0
Non-cash interest expense	0	0	106
Acquisition-related expense (benefit), net	897	(4,537)	203,183
Gain on redemption of common stock	0	(4,916)	0
Gain on E-Commerce transaction	(56,032)	0	0
Impairment of cost method investment	50,553	0	0
Change in assets and liabilities, net of acquisitions:
Restricted cash	(4,372)	(12,519)	0
Accounts receivable	10,534	(70,376)	(34,905)
Prepaid expenses and other current assets	(70,859)	(36,292)	(2,467)
Accounts payable	18,711	(20,997)	50,835
Accrued merchant and supplier payables	149,918	380,108	149,044
Accrued expenses and other current liabilities	47,742	189,127	94,592
Other, net	35,604	(5,711)	(1,856)
Net cash provided by operating activities	266,834	290,447	86,885
Investing activities
Purchases of property, equipment and software capitalization, net	(95,836)	(43,811)	(14,681)
Acquisitions of businesses, net of acquired cash	(46,890)	(14,400)	3,816
Purchases of intangible assets	(600)	(14,517)	(922)
Purchases of additional interests in consolidated subsidiaries	(14,130)	(42,663)	0
Purchases of investments	(37,523)	(32,042)	0
Changes in restricted cash	0	0	(92)
Net cash used in investing activities	(194,979)	(147,433)	(11,879)
Financing activities
Proceeds from issuance of stock, net of issuance costs	0	1,266,392	584,658
Excess tax benefit on stock-based compensation	27,023	10,178	32
Tax withholdings related to net shares settlements of restricted stock units	(12,996)	(3,770)	0
Payments of contingent acquisition liability	(4,700)	0	0
Loans from related parties	0	0	5,035
Repayments of loans with related parties	0	(14,358)	0
Repurchase of common stock	0	(353,768)	(503,173)
Dividends paid on common and preferred stock	0	0	(1,299)
Proceeds from exercise of stock options	9,313	3,008	195
Conversion of preferred stock	0	51	0
Partnership distributions to noncontrolling interest holders	(4,312)	(5,525)	0
Settlements of purchase price obligations related to acquisitions	(2,233)	0	0
Redemption of preferred stock	0	(35,003)	(55,003)
Net cash provided by financing activities	12,095	867,205	30,445
Effect of exchange rate changes on cash and cash equivalents	2,404	(6,117)	1,069
Net increase in cash and cash equivalents	86,354	1,004,102	106,520
Cash and Cash Equivalents, beginning of the period	1,122,935	118,833	12,313
Cash and Cash Equivalents, end of the period	1,209,289	1,122,935	118,833
Supplemental Cash Flow Information [Abstract]
Income Taxes Paid	126,987	1,635	140
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Issuance of common stock in connection with acquisitions	0	11,067	80,200
Contingent consideration in connection with acquisitions	3,400	17,755	63,180
Issuance of non-voting common stock in connection with investments in equity interests	0	45,218	0
Stock issued in exchange for additional interests in consolidates subsidiaries	527	10,400	0
Other current liabilities related to purchases of additional interests in consolidated subsidiaries	1,959	0	0
Contribution of investment in E-Commerce transaction	47,042	0	0
Equipment acquired under capital lease obligations	1,122	0	0
Shares issued to settle liability-classified awards	2,267	0	0
Shares issued to settle contingent consideration	236	0	266,128
Accounts payable and accrued expenses related to purchases of property, equipment and software capitalization	$ 1,891	$ 1,972	$ 2,379