Stockholders' Equity (Equity Distribution Agreement) (Details) (Maxim 2012 Agreement [Member], USD $)	0 Months Ended	3 Months Ended	0 Months Ended
	Jul. 23, 2012	Mar. 31, 2015	Oct. 05, 2012	Sep. 14, 2012
Class of Stock [Line Items]
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 sold under equity distribution agreement		21,732,904
Cash proceeds from shares sold under equity distribution agreement		5,242,000
Commissions paid on shares sold under equity distribution agreement		$ 162,000
October 5, 2012 Prospectus Supplement Increased Offering [Member]
Class of Stock [Line Items]
Number of shares to be sold under the equity distribution agreement			40,000,000
December 23, 2013 Prospectus Supplement Increased Offering [Member]
Class of Stock [Line Items]
Number of shares to be sold under the equity distribution agreement			90,000,000
Minimum [Member] | September 14, 2012 Prospectus Supplement Increased Offering [Member]
Class of Stock [Line Items]
Number of shares to be sold under the equity distribution agreement				12,000,000
Maximum [Member] | September 14, 2012 Prospectus Supplement Increased Offering [Member]
Class of Stock [Line Items]
Number of shares to be sold under the equity distribution agreement				20,000,000