CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Flows from Operating Activities:
Net loss	$ (24,116)	$ (4,982)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	1,782	1,275
Share-based compensation expense	2,871	3,254
Amortization of premium on investments	849	513
Amortization of intangibles	265	265
Loss on disposal of assets		3
Changes in operating assets and liabilities:
Accounts receivable	5,415	5,799
Unbilled revenue	(432)	1,652
Prepaid expenses and other current assets	1,314	(525)
Accounts payable	63	4,712
Accrued expenses	(2,342)	(2,297)
Deferred revenue	(1,023)	31,890
Other current liabilities	(142)	202
Other long-term liabilities	(55)	(64)
Net cash (used in) provided by operating activities	(15,551)	41,697
Cash Flows from Investing Activities:
Purchases of property and equipment	(802)	(8,203)
Purchases of marketable securities	(108,817)	(189,362)
Proceeds from maturities of marketable securities	110,778	144,545
Proceeds from sales of marketable securities	3,822
Net cash provided by (used in) investing activities	4,981	(53,020)
Cash Flows from Financing Activities:
Proceeds from issuance of common stock under stock plans	868	735
Net cash provided by financing activities	868	735
Decrease in cash and cash equivalents	(9,702)	(10,588)
Cash and cash equivalents, beginning of period	52,990	49,245
Cash and cash equivalents, end of period	$ 43,288	$ 38,657