Convertible Preferred Stock And Stockholders' Deficit - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended				12 Months Ended			12 Months Ended							12 Months Ended						12 Months Ended					12 Months Ended					12 Months Ended					12 Months Ended			1 Months Ended	4 Months Ended						12 Months Ended					2 Months Ended			12 Months Ended
	Jan. 31, 2011	Dec. 31, 2012 Person	Dec. 31, 2011	Dec. 31, 2010	Feb. 28, 2010	Dec. 31, 2012 2012 Equity Incentive Plan	Dec. 31, 2012 2012 Equity Incentive Plan Common stock shares outstanding	Dec. 31, 2012 2012 Equity Incentive Plan 2011 stock plan	Dec. 31, 2012 Stock Awards	Dec. 31, 2011 Stock Awards	Dec. 31, 2010 Stock Awards	Dec. 31, 2012 Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario one	Dec. 31, 2011 Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario one	Dec. 31, 2012 Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario one 2012 Equity Incentive Plan	Dec. 31, 2012 Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario two 2012 Equity Incentive Plan	Dec. 31, 2012 Minimum Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario one	Dec. 31, 2011 Minimum Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario one	Dec. 31, 2012 Minimum Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario two	Dec. 31, 2011 Minimum Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario two	Dec. 31, 2012 Series A Preferred Stock	Dec. 31, 2011 Series A Preferred Stock	Dec. 31, 2012 Series A Preferred Stock Prior To October Thirty First Two Thousand Thirteen	Dec. 31, 2011 Series A Preferred Stock Original purchase price	Dec. 31, 2010 Series A Preferred Stock Original purchase price	Dec. 31, 2012 Series B-1 Preferred Stock	Dec. 31, 2011 Series B-1 Preferred Stock	Dec. 31, 2012 Series B-1 Preferred Stock Prior To October Thirty First Two Thousand Thirteen	Dec. 31, 2011 Series B-1 Preferred Stock Original purchase price	Dec. 31, 2010 Series B-1 Preferred Stock Original purchase price	Dec. 31, 2012 Series B-2 Preferred Stock	Dec. 31, 2011 Series B-2 Preferred Stock	Dec. 31, 2012 Series B-2 Preferred Stock Prior To October Thirty First Two Thousand Thirteen	Dec. 31, 2011 Series B-2 Preferred Stock Original purchase price	Dec. 31, 2010 Series B-2 Preferred Stock Original purchase price	Dec. 31, 2012 Series C Preferred Stock	Dec. 31, 2011 Series C Preferred Stock	Dec. 31, 2012 Series C Preferred Stock Prior To October Thirty First Two Thousand Thirteen	Dec. 31, 2011 Series C Preferred Stock Original purchase price	Dec. 31, 2010 Series C Preferred Stock Original purchase price	Mar. 31, 2009 Series D Preferred Stock	Dec. 31, 2008 Series D Preferred Stock	Dec. 31, 2012 Series D Preferred Stock	Dec. 31, 2011 Series D Preferred Stock	Sep. 30, 2008 Series D Preferred Stock	Dec. 31, 2012 Series D Preferred Stock Maximum Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario two	Dec. 31, 2011 Series D Preferred Stock Maximum Automatically converted in to one fully paid and non assessable share of common stock at earlier of , scenario two	Dec. 31, 2012 Series D Preferred Stock Prior To October Thirty First Two Thousand Thirteen	Dec. 31, 2011 Series D Preferred Stock Original purchase price	Dec. 31, 2010 Series D Preferred Stock Original purchase price	Dec. 31, 2012 Series D Preferred Stock Additional distribution required before any proceeds would be distributed pro rata based on the number of shares held	Dec. 31, 2011 Series D Preferred Stock Additional distribution required before any proceeds would be distributed pro rata based on the number of shares held	Jun. 30, 2012 Series E Preferred Stock	Dec. 31, 2012 Series E Preferred Stock	Dec. 31, 2011 Series E Preferred Stock	Dec. 31, 2012 Series E Preferred Stock Starting From October Thirty First Two Thousand Thirteen Minimum	Dec. 31, 2012 Series E Preferred Stock Starting From October Thirty First Two Thousand Thirteen Maximum	Dec. 31, 2012 Series E Preferred Stock Prior To October Thirty First Two Thousand Thirteen	Dec. 31, 2011 Series E Preferred Stock Original purchase price	Dec. 31, 2010 Series E Preferred Stock Original purchase price	Dec. 31, 2012 Series E Preferred Stock Additional distribution required before any proceeds would be distributed pro rata based on the number of shares held	Dec. 31, 2011 Series E Preferred Stock Additional distribution required before any proceeds would be distributed pro rata based on the number of shares held
Capital Unit [Line Items]
Convertible preferred stock, shares authorized																																								431,973	1,015,357			1,749,425								1,672,300
Preferred Stock, issued per share amount																																								$ 11.57	$ 11.57			$ 11.57								$ 12.11
Proceed from issuance of Convertible preferred stock																$ 30,000,000	$ 30,000,000																							$ 5,000,000	$ 32,000,000											$ 20,300,000
Redemption amount of outstanding Convertible preferred stock																				$ 10.26	$ 10.26		$ 5.13	$ 5.13	$ 15.39	$ 15.39		$ 5.13	$ 5.13	$ 15.39	$ 15.39		$ 5.13	$ 5.13	$ 25.64	$ 25.64		$ 10.26	$ 10.26			$ 28.92	$ 28.92		$ 28.92	$ 28.92		$ 11.57	$ 11.57	$ 17.34	$ 17.34		$ 30.27	$ 30.27				$ 12.11	$ 12.11	$ 18.16	$ 18.16
Annual noncumulative dividends entitled by preferred stock share holders for each outstanding share held																						$ 0.43					$ 0.43					$ 0.43					$ 0.8206										$ 0.93								$ 0.61	$ 1.21	$ 0.61
Liquidation preference per share																									$ 5.13	$ 5.13				$ 5.13	$ 5.13				$ 10.26	$ 10.26						$ 11.57	$ 11.57										$ 12.11	$ 12.11
Convertible preferred stock, pre-IPO Valuation amount												225,000,000	225,000,000			225,000,000	225,000,000
Convertible preferred stock, voting right percentage																		60.00%	60.00%
Convertible Preferred Stock, conversion basis		Each share of convertible preferred stock is convertible, at the option of the holder, at any time after the date of issuance, into one fully paid and nonassessable share of common stock, subject to certain anti-dilution adjustments	Each share of convertible preferred stock is convertible, at the option of the holder, at any time after the date of issuance, into one fully paid and nonassessable share of common stock, subject to certain anti-dilution adjustments
Number of board of directors on which holders of preferred stock holders are entitled to elect		2
Minimum shares of preferred stock required to participate in future equity issuance		280,782	280,782
Convertible preferred stock, gross proceed												30,000,000	30,000,000
Number of Shares authorized to be issued under plan	141,795	3,408,247			153,026		1,123,131	1,066,975
Vesting period		4 years				4 years
Vesting period expires		10 years				10 years
Percentage of increase in number of shares reserved for issuance														5.00%
Number of increase in number of shares reserved for issuance															842,348
Fiscal year over which number of shares reserved for issuance will increase, starting year						2013
Fiscal year over which number of shares reserved for issuance will increase, ending year						2022
Equity Incentive Plan period		10 years
Awards, common stock vested	56,998
Stock-based compensation expense		821,000	221,000	299,000					401,000	52,000	92,000
Options vested		592,950
Options outstanding		1,030,795
Weighted-average remaining contractual life of options exercisable		6 years	6 years 4 months 24 days
Aggregate intrinsic value of options outstanding and exercisable		8,900,000	1,100,000
Aggregate intrinsic value of options vested and expected to vest		10,400,000
Options vested and expected to vest, average remaining contractual life		7 years 4 months 24 days
Weighted-average fair value-based measurement of employee and director stock option granted		$ 6.98	$ 0.82	$ 1.07
Unrecognized compensation expense		2,800,000
Weighted-average period		3 years 3 months 18 days
Total intrinsic value of options exercised		$ 607,000