CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net loss	$ (12,405)	$ (10,040)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	9,227	6,011
Amortization of intangible assets	6,511	4,013
Stock-based compensation, net of forfeitures	11,538	9,617
(Gain)/Loss on disposal of property and equipment	188	(402)
Deferred income taxes	3,387	(1,248)
Tax benefit from stock-based compensation	11,755	16,334
Excess tax benefits from stock-based compensation	(12,279)	(16,334)
Changes in operating assets and liabilities:
Accounts receivable, net	2,859	(381)
Inventories	186	27
Prepaid expenses and other current assets	(28,349)	(23,204)
Other assets	(6,897)	(2,253)
Accounts payable	(13,944)	(2,257)
Accrued and other liabilities	(54,599)	(28,764)
Deferred revenue	(337)	1,072
Other non-current liabilities	(345)	(152)
Net cash used in operating activities	(83,504)	(47,961)
Cash flows from investing activities:
Acquisition of business and intangibles, net of cash acquired	(1,031)	0
Purchases of property and equipment	(15,033)	(5,037)
Capitalization of software and website development costs	(3,495)	(3,072)
Proceeds from sale of equipment	0	410
Net cash used in investing activities	(19,559)	(7,699)
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of stock options	12,390	3,345
Repurchases of common stock	(2,241)	0
Excess tax benefits from stock-based compensation	12,279	16,334
Net cash provided by financing activities	22,428	19,679
Net decrease in cash and cash equivalents	(80,635)	(35,981)
Cash and cash equivalents, beginning of period	245,088	179,915
Cash and cash equivalents, end of period	164,453	143,934
Supplemental schedule of non-cash activities
Net increase/(decrease) in accrued purchases of property and equipment	(4,201)	1,462
Increase in estimated fair market value of building under build-to-suit lease	2,716	0
Amount due from adjustment of net working capital from acquired business	$ 465	$ 0