Stockholders' Equity (Equity Distribution Agreement) (Details) (USD $)	3 Months Ended		0 Months Ended	3 Months Ended	0 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Shares Sold In Current Period [Member]	Oct. 05, 2012 Maxim 2012 Agreement [Member]	Mar. 31, 2013 Maxim 2012 Agreement [Member]	Sep. 14, 2012 Minimum [Member] Maxim 2012 Agreement [Member]	Sep. 14, 2012 Maximum [Member] Maxim 2012 Agreement [Member]
Maximum dollar amount of shares under the EDA				$ 75,000,000
Fixed commission rate for gross proceeds $10,000,000 or less (percent)				4.00%
Gross proceeds from common stock, threshold	10,000,000
Fixed commission rate for gross proceeds in excess of $10,000,000 (percent)				3.00%
Number of shares to be sold under the equity distribution agreement			40,000,000		12,000,000	20,000,000
Number of shares sold under equity distribution agreement		0		29,500,000
Cash proceeds from shares sold under equity distribution agreement		0		23,003,000
Commissions paid on shares sold under equity distribution agreement				$ 820,000