Reconciliation of Basic and Diluted Net Income (Loss) Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
Net income (loss)	$ (24,921)	$ 14,318	$ (42,674)	$ 46,167
Weighted-average shares outstanding:
Basic (in shares)	44,911	44,370	44,860	41,924
Assumed conversion of employee stock options (in shares)		299		335
Assumed conversion of warrants (in shares)		7,561		10,048
Diluted (in shares)	44,911	52,230	44,860	52,307
Net income (loss) per share:
Basic (in dollars per share)	$ (0.55)	$ 0.32	$ (0.95)	$ 1.10
Diluted (in dollars per share)	$ (0.55)	$ 0.27	$ (0.95)	$ 0.88