Preferred Stock - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended		9 Months Ended					1 Months Ended	9 Months Ended	12 Months Ended		1 Months Ended	2 Months Ended	4 Months Ended	9 Months Ended	12 Months Ended			1 Months Ended	9 Months Ended	12 Months Ended		1 Months Ended		9 Months Ended	12 Months Ended		1 Months Ended			9 Months Ended	12 Months Ended		1 Months Ended	9 Months Ended	12 Months Ended			9 Months Ended
	Aug. 31, 2008	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Next sale and issuance of capital stock of the Company	Sep. 30, 2013 Scenario two Minimum	Sep. 30, 2013 Scenario two Next sale and issuance of capital stock of the Company	Sep. 30, 2013 Scenario two Next sale and issuance of capital stock of the Company Minimum	Sep. 30, 2013 Scenario two Next sale and issuance of capital stock of the Company Maximum	Aug. 31, 2008 Series A-1 Preferred	Sep. 30, 2013 Series A-1 Preferred	Dec. 31, 2012 Series A-1 Preferred	Sep. 30, 2012 Series A-1 Preferred	Aug. 31, 2008 Series B-1 Preferred	Dec. 31, 2004 Series B-1 Preferred	Dec. 31, 2003 Series B-1 Preferred	Sep. 30, 2013 Series B-1 Preferred	Dec. 31, 2012 Series B-1 Preferred	Dec. 31, 2009 Series B-1 Preferred	Sep. 30, 2012 Series B-1 Preferred	Aug. 31, 2006 Series C-1 Preferred	Sep. 30, 2013 Series C-1 Preferred	Dec. 31, 2012 Series C-1 Preferred	Sep. 30, 2012 Series C-1 Preferred	Aug. 31, 2008 Series D-1 Preferred	Apr. 30, 2007 Series D-1 Preferred	Sep. 30, 2013 Series D-1 Preferred	Dec. 31, 2012 Series D-1 Preferred	Sep. 30, 2012 Series D-1 Preferred	Dec. 30, 2010 Series E Preferred	Jun. 30, 2010 Series E Preferred	Nov. 30, 2009 Series E Preferred	Sep. 30, 2013 Series E Preferred	Dec. 31, 2012 Series E Preferred	Sep. 30, 2012 Series E Preferred	Aug. 31, 2008 Warrants	Sep. 30, 2013 Series E- Three Convertible Preferred Stock	Dec. 31, 2012 Series E- Three Convertible Preferred Stock	Dec. 31, 2010 Series E- Three Convertible Preferred Stock	Sep. 30, 2012 Series E- Three Convertible Preferred Stock	Sep. 30, 2013 Series B One Preferred Stock Scenario one, conversion basis	Sep. 30, 2013 Series D-1 And E Preferred Stock Scenario one, conversion basis
Temporary Equity [Line Items]
Redeemable convertible preferred stock converted		46,626,294
Issuance of common stock upon conversion of redeemable convertible preferred stock		2,793,281
Conversion of preferred stock to common stock		$ 323,155,000
Convertible preferred stock issued		0	624,426								12,734			188,894	136,520		373,223			27,345		27,345			137,592		136,949						39,265				71,543
Convertible preferred stock outstanding		0	624,426								12,734						373,223					27,345					136,949						39,265				71,543
Preferred stock, shares authorized		10,000,000
Preferred stock, par value		$ 0.0001
Preferred stock, shares issued		0
Preferred stock, shares outstanding		0
Purchase price per share of preferred stock		$ 5.00								$ 232.93				$ 232.93	$ 232.93	$ 232.93				$ 365.70	$ 365.70				$ 232.94	$ 232.94						$ 232.93
Preferred stock balances, price per share										$ 18.64						$ 18.64					$ 29.26					$ 18.64						$ 18.64
Proceed from issuance of redeemable preferred stock														44,000,000	31,800,000										32,000,000
Warrant to purchase common stock, issued														29,245											20,639
Warrant issued, exercise price per share														30.21											22.13
Common stock, price per share														$ 1.51
Warrant issued, exercise period														5 years											5 years
Warrant, extended expiration date																	Apr. 01, 2013	Dec. 31, 2011
Percentage of reduction in number of shares exercisable																	45.00%
Proceed from issuance of redeemable preferred stock																				10,000,000
Repurchase of Stock, shares									646				1,610											472											71
Repurchase of Stock, value	82,000
Shares issued upon conversion of debt																													37,119	859	1,288							71,543
Aggregate cumulative dividend										2,300,000	2,200,000					63,100,000	59,600,000				5,600,000	5,100,000				15,900,000	14,600,000					1,900,000	1,500,000			3,400,000	2,700,000
Aggregate cumulative dividend, per share										$ 183.64	$ 174.40					$ 168.96	$ 159.72				$ 201.83	$ 187.32				$ 116.00	$ 106.75					$ 48.14	$ 38.90			$ 47.28	$ 38.04
Preferred stock liquidation preference												$ 232.93							$ 232.93				$ 365.70					$ 232.94						$ 290.97					$ 465.87
Conversion basis, Percentage of outstanding common stock																																								66.67%	51.00%
Per Share Price					$ 8.00
Aggregate gross proceed					$ 30,000,000
Participation percentage in financing							1.00%	99.00%
Conversion ratio						0.25
Participation right, description				Any holder that participated in the 2013 financing for between 100% and 300% of such holder's Pro Rata Share (the "Participation Multiple") had each shares of preferred stock convert into shares of common stock by multiplying the product of (y) the aggregate number of shares of preferred stock held by such holder multiplied by the applicable Participation Multiple and (z) four (4).