Analysis of Deferred Tax Assets (Liabilities) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Net operating loss carryforwards	$ 85,600	$ 87,270
Difference in depreciation and amortization	2,524	2,574
Capital loss carryforward	0	5
Research and development tax credits	20,012	20,740
Stock compensation	4,424	4,153
Deferred rent	265	372
Deferred revenue	1,133	1,124
Other	169	571
Deferred tax asset, gross	114,127	116,809
Valuation allowance	(114,127)	(116,809)
Net deferred tax asset	$ 0	$ 0