Net Loss Per Shares (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended					1 Months Ended	6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013	Sep. 30, 2013 Warrants	Jul. 14, 2011 Warrants	Jul. 31, 2011 0.75% Convertible Senior Notes Due 2016	Sep. 30, 2013 0.75% Convertible Senior Notes Due 2016	Jul. 14, 2011 0.75% Convertible Senior Notes Due 2016
Antidilutive Securities Excluded from Computation of Net Loss Per Share
Antidilutive securities excluded from computation of net loss per share	8	2	8	2
Contractual interest rate of 0.75% Convertible Senior Notes due 2016	0.75%		0.75%		0.75%				0.75%	0.75%
Convertible Senior Notes due description								2016	2016
Conversion price per share									$ 31.74	$ 31.74
Warrants, Conversion price per share						41.14	41.14