Schedule of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Stock Options
Number of Shares
Number of Shares, Outstanding at December 31, 2011	3,648
Number of Shares, Granted	1,196
Number of Shares, Cancelled	(740)
Number of Shares, Outstanding at June 30, 2012	4,104	3,648
Number of Shares, Exercisable at June 30, 2012	1,782
Weighted Average Exercise Price
Weighted-Average Exercise Price Per Share, Outstanding at December 31, 2011	$ 7.98
Weighted-Average Exercise Price Per Share, Granted	$ 1.74
Weighted-Average Exercise Price Per Share, Cancelled	$ 8.88
Weighted-Average Exercise Price Per Share, Outstanding at June 30, 2012	$ 6.05	$ 7.98
Weighted-Average Exercise Price Per Share, Exercisable at June 30, 2012	$ 7.28
Weighted Average Remaining Contractual Term (in years)
Weighted Average Remaining Contractual Term (in years), Outstanding	7 years 11 months 16 days	7 years 9 months 18 days
Weighted Average Remaining Contractual Term (in years), Outstanding	7 years 11 months 16 days	7 years 9 months 18 days
Weighted Average Remaining Contractual Term (in years), Exercisable at June 30, 2012	6 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value of In-the-Money Options, Outstanding at June 30, 2012
Stock Options That Contain Performance And Market-Based Conditions
Number of Shares
Number of Shares, Outstanding at December 31, 2011	440
Number of Shares, Cancelled	(250)
Number of Shares, Outstanding at June 30, 2012	190	440
Number of Shares, Exercisable at June 30, 2012	40
Weighted Average Exercise Price
Weighted-Average Exercise Price Per Share, Outstanding at December 31, 2011	$ 9.75
Weighted-Average Exercise Price Per Share, Cancelled	$ 9.23
Weighted-Average Exercise Price Per Share, Outstanding at June 30, 2012	$ 10.43	$ 9.75
Weighted-Average Exercise Price Per Share, Exercisable at June 30, 2012	$ 13.81
Weighted Average Remaining Contractual Term (in years)
Weighted Average Remaining Contractual Term (in years), Outstanding	8 years 6 months 18 days	9 years 26 days
Weighted Average Remaining Contractual Term (in years), Outstanding	8 years 6 months 18 days	9 years 26 days
Weighted Average Remaining Contractual Term (in years), Exercisable at June 30, 2012	7 years 5 months 1 day
Aggregate Intrinsic Value
Aggregate Intrinsic Value of In-the-Money Options, Outstanding at June 30, 2012