Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Weighted-average shares outstanding for basic and diluted net income per share
Net income (in dollars)	$ 15,497	$ 18,983
Basic net income per share:
Weighted-average shares outstanding - Basic	59,281	58,362
Basic net income per common share (in usd per share)	$ 0.26	$ 0.33
Diluted net income per share:
Weighted-average shares outstanding - Basic	59,281	58,362
Effect of potentially dilutive securities	107	438
Weighted-average shares outstanding - Diluted	59,388	58,800
Diluted net income per common share (in usd per share)	$ 0.26	$ 0.32