Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Weighted-average shares outstanding for basic and diluted net income per share
Net income (in dollars)	$ 15,626	$ 21,105	$ 46,814	$ 60,584
Basic net income per share:
Weighted-average shares outstanding - Basic	59,400	58,847	59,343	58,623
Basic net income per common share (in usd per share)	$ 0.26	$ 0.36	$ 0.79	$ 1.03
Diluted net income per share:
Weighted-average shares outstanding - Basic	59,400	58,847	59,343	58,623
Effect of potentially dilutive securities	5	281	68	320
Weighted-average shares outstanding - Diluted	59,405	59,128	59,411	58,943
Diluted net income per common share (in usd per share)	$ 0.26	$ 0.36	$ 0.79	$ 1.03