Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Weighted-average shares outstanding for basic and diluted net income per share
Net income (in dollars)	$ 10,121	$ 15,691	$ 23,066	$ 31,188
Basic net income per share:
Weighted-average shares outstanding - Basic	59,734	59,347	59,647	59,314
Basic net income per common share (in usd per share)	$ 0.17	$ 0.26	$ 0.39	$ 0.53
Diluted net income per share:
Weighted-average shares outstanding - Basic	59,734	59,347	59,647	59,314
Effect of potentially dilutive securities	17	39	16	72
Weighted-average shares outstanding - Diluted	59,751	59,386	59,663	59,386
Diluted net income per common share (in usd per share)	$ 0.17	$ 0.26	$ 0.39	$ 0.53