Basic and Diluted Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income (loss)	$ 18,641	$ 12,278	$ 252,096	$ (4,925)
Weighted-average shares outstanding:
Basic (in shares)	56,778	46,606	51,340	46,469
Assumed conversion of employee stock grants (in shares)	2,159	2,122	2,384	0
Assumed conversion of warrants (in shares)	0	6,568	4,707	0
Diluted (in shares)	58,937	55,296	58,431	46,469
Net income (loss) per basic share (in usd per share)	$ 0.33	$ 0.26	$ 4.91	$ (0.11)
Net income (loss) per diluted share (in usd per share)	$ 0.32	$ 0.22	$ 4.31	$ (0.11)
Common stock equivalents that could potentially dilute net income per basic share in the future, but were not included in the computation of diluted earnings per share because the impact would have been antidilutive
Common stock equivalents (in shares)	164	800	134	2,760
Assumed conversion of warrants
Common stock equivalents that could potentially dilute net income per basic share in the future, but were not included in the computation of diluted earnings per share because the impact would have been antidilutive
Common stock equivalents (in shares)	0	0	0	5,913