Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Net Income Per Share Details
Net income available to common stockholders	$ 8,617	$ 1,947
Common shares	70,717	62,264
Denominator for basic calculation	70,717	62,264
Employee stock options	2,759	3,168
Stock purchase rights	309	352
Employee stock purchase plan	325	24
Denominator for diluted calculation	74,110	65,808
Net income per share
Basic	$ 0.12	$ 0.03
Diluted	$ 0.12	$ 0.03