Stock-Based Compensation - Narrative (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended		12 Months Ended	6 Months Ended	7 Months Ended		12 Months Ended			12 Months Ended		12 Months Ended					12 Months Ended		1 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Stock Options [Member]	May 31, 2012 Employee Stock [Member]	Nov. 30, 2012 Employee Stock [Member]	Nov. 30, 2011 Employee Stock [Member]	Dec. 31, 2012 Employee Stock [Member]	May 31, 2012 Employee Stock [Member] Purchase_Period	Dec. 31, 2011 Employee Stock [Member]	Dec. 31, 2012 2006 Plan [Member]	Dec. 31, 2006 2006 Plan [Member]	Dec. 31, 2012 2006 Plan [Member] Stock Options [Member]	Dec. 31, 2012 2006 Plan [Member] Monthly Vesting Period [Member]	Dec. 31, 2012 2006 Plan [Member] Annual Vesting Period [Member] Stock Options [Member]	Dec. 31, 2012 2010 Plan [Member]	Nov. 29, 2010 2010 Plan [Member]	Dec. 31, 2012 2010 Plan [Member] Monthly Vesting Period [Member]	Dec. 31, 2012 2010 Plan [Member] Annual Vesting Period [Member]	Jun. 30, 2012 Restated 2010 Plan [Member]	Dec. 31, 2012 Restated 2010 Plan [Member]	Dec. 31, 2011 Restated 2010 Plan [Member]	Dec. 31, 2012 Maximum [Member] Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved											1,134,000					2,243,668			9,300,000
Expected term										10 years					10 years
Vesting term												4 years			4 years
Vesting rights percentage													2.08333%	25.00%			2.08333%	25.00%
Percent of additional shares authorized provision																			4.00%
Shares available for future issuance							463,973		577,852											701,976	1,103,579
Percentage of purchase price							85.00%
Maximum percentage of employee withholding							20.00%
Maximum number of shares per employee							20,000
Number of purchase periods								2
Offering period							6 months															27 months
Exercised (in shares)				225,053	138,826	172,148
Common stock price (in usd per share)	$ 1.33
Weighted average fair value of options outstanding (in usd per share)	$ 2.64	$ 4.01
Total unrecognized compensation costs			$ 12,047
Recognition over weighted average periods	3 years 3 months 18 days		2 years 10 months 24 days
Unvested stock options outstanding (in shares)	157,000
Unrecognized compensation expense	$ 138