Stockholders' Equity (Details) (USD $)	2 Months Ended	9 Months Ended			1 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended			1 Months Ended
	Mar. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Oct. 31, 2012 Controlled equity offering programme	Sep. 30, 2012 Controlled equity offering programme	Jan. 31, 2012 Controlled equity offering programme	Sep. 30, 2012 Controlled equity offering programme	Sep. 30, 2012 Controlled equity offering programme	Dec. 31, 2011 Controlled equity offering programme	Oct. 30, 2012 Controlled equity offering programme	Jan. 31, 2011 Controlled equity offering programme	Sep. 30, 2012 Controlled equity offering programme Maximum
Stockholders' Equity
Common stock the company could issue or sell (in shares)		297,000,000		297,000,000		5,000,000		5,000,000	5,000,000			297,000,000
Aggregate offering price of additional shares which the entity can issue as per amended agreement													$ 44,000,000
Fixed commission rate (as a percent)								0.03
Notice period for termination of agreement									10 days
Common stock issued (in shares)		60,807,350		44,210,636	1,167,770	57,100	2,450,000	57,100	57,100	575,000
Net proceeds from issuance of common stock		62,872,000	35,880,000		7,000,000	300,000	8,500,000	10,600,000		2,200,000
Common stock available for sale (in shares)								1,975,000
Remaining aggregate offering price available under the Cantor Amendment											36,400,000
Common stock in an underwritten public offering issued (in shares)	12,075,000
Shares issued on exercise of over-allotment option by underwriters (in shares)	1,575,000
Net proceeds from sale of stock in an underwritten public offering		$ 43,400,000