Net Income Per Share (Diluted) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:
Net income	$ 20,781	$ 505	$ 64,042	$ 14,122
Interest on convertible notes, net of tax	691	0	3,292	0
Numerator for Diluted Net Income Per Common Share	$ 21,472	$ 505	$ 67,334	$ 14,122
Denominator:
Weighted average common shares outstanding	137,380	137,147	137,942	136,671
Conversion of notes	6,020	0	10,816	0
Share purchase options	2,818	2,854	2,592	2,530
Restricted share units	449	680	438	669
Adjusted weighted average common shares outstanding	146,667	140,681	151,788	139,870
Diluted net income per common share	$ 0.15	$ 0.00	$ 0.44	$ 0.10