CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net loss	$ (15,361)	$ (38,045)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	6,028	4,576
Provision for doubtful accounts	(149)	0
Amortization of deferred financing costs	24	123
Accretion on premium on short-term investments	347	445
Deferred income taxes	545	32,220
Stock-based compensation	11,343	9,607
Income tax charge from stock-based compensation	264	362
Changes in operating assets and liabilities:
Accounts receivable	4,189	2,586
Prepaid expenses and other	(1,204)	(811)
Accounts payable	(558)	(877)
Accrued taxes	752	298
Accrued compensation and benefits	3,291	(4,820)
Accrued liabilities and other	2,156	4,145
Net cash provided by operating activities	11,667	9,809
Cash flows from investing activities
Acquisition of property and equipment	(2,224)	(11,244)
Purchases of short-term investments	(26,647)	(24,186)
Sales of short-term investments	3,154	6,210
Maturities of short-term investments	1,250	11,820
Net cash used in investing activities	(24,467)	(17,400)
Cash flows from financing activities
Repayment on capital leases obligations	(161)	(155)
Proceeds from common stock issuances	13,612	7,818
Income tax charge from stock-based compensation	(264)	(362)
Net cash provided by financing activities	13,187	7,301
Net increase (decrease) in cash and cash equivalents	387	(290)
Effect of exchange rate changes on cash and cash equivalents	448	(107)
Cash and cash equivalents at beginning of period	76,568	65,983
Cash and cash equivalents at end of period	$ 77,403	$ 65,586