Schedule of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Stock Options
Number of Shares
Number of Shares, Outstanding Beginning Balance	3,648,000
Granted	1,806,000
Cancelled	(1,427,000)
Number of Shares, Outstanding Ending Balance	4,027,000	3,648,000
Exercisable at December 31, 2012	2,047,000
Weighted Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Outstanding Beginning Balance	$ 7.98
Weighted-Average Exercise Price Per Share, Granted	$ 1.75
Weighted-Average Exercise Price Per Share, Cancelled	$ 8.22
Weighted-Average Exercise Price Per Share, Outstanding Ending Balance	$ 5.16	$ 7.98
Weighted-Average Exercise Price Per Share, Exercisable at December 31, 2012	$ 6.10
Weighted Average Remaining Contractual Term (in years)
Weighted Average Remaining Contractual Term (in years), Outstanding	7 years 9 months 4 days	7 years 9 months 22 days
Weighted Average Remaining Contractual Term (in years), Outstanding	7 years 9 months 4 days	7 years 9 months 22 days
Weighted Average Remaining Contractual Term (in years), Exercisable at December 31, 2012	6 years 6 months 29 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value of In-the-Money Options, Outstanding at December 31, 2012	$ 208
Aggregate Intrinsic Value of In-the-Money Options, Exercisable at December 31, 2012	88
Stock Options That Contain Performance And Market-Based Conditions
Number of Shares
Number of Shares, Outstanding Beginning Balance	440,000
Granted	830,000
Cancelled	(317,000)
Number of Shares, Outstanding Ending Balance	953,000	440,000
Exercisable at December 31, 2012	40,000
Weighted Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Outstanding Beginning Balance	$ 9.75
Weighted-Average Exercise Price Per Share, Granted	$ 2.07
Weighted-Average Exercise Price Per Share, Cancelled	$ 7.75
Weighted-Average Exercise Price Per Share, Outstanding Ending Balance	$ 3.73	$ 9.75
Weighted-Average Exercise Price Per Share, Exercisable at December 31, 2012	$ 13.81
Weighted Average Remaining Contractual Term (in years)
Weighted Average Remaining Contractual Term (in years), Outstanding	9 years 3 months 18 days	9 years 26 days
Weighted Average Remaining Contractual Term (in years), Outstanding	9 years 3 months 18 days	9 years 26 days
Weighted Average Remaining Contractual Term (in years), Exercisable at December 31, 2012	6 years 10 months 28 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value of In-the-Money Options, Outstanding at December 31, 2012	$ 74