Description of Business (Equity Facility) (Details) (Equity Facility, 2011, USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended
	Aug. 31, 2011	Mar. 31, 2013 transactions
Equity Facility, 2011
Equity Facility:
Maximum draw-down amount	$ 50
Term	2 years
Draw-down transaction restriction, minimum common stock price (per share)	$ 4
Number of completed draw-down transactions		0