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	$ (52,965)	$ (15,149)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	3,591	2,838
Share-based compensation expense	6,201	6,711
Amortization of premium on investments	1,743	1,211
Amortization of intangibles	530	531
Impairment of equity investment	244
Loss on disposal of assets		3
Changes in operating assets and liabilities:
Accounts receivable	7,712	8,819
Unbilled revenue	(668)	1,711
Prepaid expenses and other current assets	612	(287)
Restricted cash		(2,471)
Accounts payable	(829)	(867)
Accrued expenses	(87)	1,619
Deferred revenue	(2,049)	30,526
Other current liabilities	(224)	213
Other long-term liabilities	(110)	(133)
Net cash (used in) provided by operating activities	(36,299)	35,275
Cash Flows from Investing Activities:
Purchases of property and equipment	(3,594)	(11,863)
Purchases of marketable securities	(152,367)	(318,643)
Proceeds from maturities of marketable securities	160,680	312,708
Proceeds from sales of marketable securities	3,822
Net cash provided by (used in) investing activities	8,541	(17,798)
Cash Flows from Financing Activities:
Proceeds from issuance of common stock under stock plans	1,282	1,605
Net cash provided by financing activities	1,282	1,605
(Decrease) increase in cash and cash equivalents	(26,476)	19,082
Cash and cash equivalents, beginning of period	52,990	49,245
Cash and cash equivalents, end of period	$ 26,514	$ 68,327