Net Income Per Share (Calculations Of Basic And Diluted Net Income Per Share And Potential Common Shares) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Net Income Per Share [Abstract]
Net income	$ 12,947	$ 10,031	$ 7,051	$ 2,399	$ 10,771	$ 11,101	$ 8,248	$ 7,145	$ 32,428	$ 37,265	$ 27,917
Weighted average common shares outstanding									42,035	42,059	40,691
Basic net income per share									$ 0.77	$ 0.89	$ 0.69
Weighted average stock options									154	320	711
Weighted average restricted stock units									561	594	513
Diluted weighted average shares									42,750	42,973	41,915
Diluted net income per share	$ 0.30	$ 0.24	$ 0.17	$ 0.06	$ 0.25	$ 0.26	$ 0.19	$ 0.17	$ 0.76	$ 0.87	$ 0.67