Redeemable Convertible Preferred Stock (Details) (USD $)	3 Months Ended		6 Months Ended				4 Months Ended			1 Months Ended				1 Months Ended			1 Months Ended			1 Months Ended			1 Months Ended	6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 series	Jun. 30, 2011	Apr. 30, 2012	Dec. 31, 2011	Jun. 30, 2004 Series A Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Series A Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Series A Redeemable Convertible Preferred Stock [Member]	Mar. 31, 2005 Series A1 Redeemable Convertible Preferred Stock [Member]	Nov. 30, 2004 Series A1 Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Series A1 Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Series A1 Redeemable Convertible Preferred Stock [Member]	Feb. 28, 2005 Series B Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Series B Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Series B Redeemable Convertible Preferred Stock [Member]	Apr. 30, 2006 Series B1 Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Series B1 Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Series B1 Redeemable Convertible Preferred Stock [Member]	May 31, 2006 Series C Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Series C Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Series C Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2007 Series D Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Series D Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Series D Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Redeemable Convertible Preferred Stock [Member]	Dec. 31, 2011 Redeemable Convertible Preferred Stock [Member]	Jun. 30, 2012 Minimum [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	26,876,384		26,876,384			26,876,384		6,600,000	6,600,000			1,176,051	1,176,051		4,989,308	4,989,308		2,138,275	2,138,275		3,897,084	3,897,084		8,075,666	8,075,666
Number of series of preferred stock issued			6
Redeemable convertible preferred stock, redemption price (usd per share)							$ 1			$ 1.403	$ 2			$ 1.403			$ 1.403			$ 2.983			$ 20.727
Proceeds from issuance of redeemable convertible preferred stock							$ 6,600,000				$ 1,650,000			$ 7,000,000			$ 3,000,000			$ 11,500,000			$ 166,000,000
Temporary equity, stock issued during period (shares)							6,600,000			351,051	825,000			4,989,308			2,138,275			3,855,180			8,008,842
Expenses paid for issuance of redeemable convertible preferred stock																							278,000
Dividend rate entitled to preferred stockholdres																										6.00%
Accumulated and unpaid dividends																										57,617,000	51,745,000
Number of shares entited by rights issued					352,178																41,904			62,000
Exercise price of rights (usd per share)					26																2.983			20.73
Share price lower threshold	$ 27		$ 27
Deemed dividend resulting from modification of redeemable convertible preferred stock	2,929,000	0	2,929,000	0
Liquidation preference, multiplier			1.5
Liquidation preference per share (usd per share)								$ 1.50				$ 2.104			$ 2.104			$ 2.104			$ 4.475			$ 31.09
Automatic converstion threshold, gross proceeds upon completion of IPO																												$ 25,000,000
Automatic converstion threshold, minimum share price (usd per share)			$ 31.09
Automatic converstion threshold, votes needed			58.00%																					67.00%