Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Mar. 31, 2008	$ 113,705	$ 274	$ 75,556	$ 38,071	$ (196)
Beginning balance, Shares at Mar. 31, 2008		27,448
Exercise of stock options	12,519	7	12,512
Exercise of stock options, Shares		697
Tax benefit resulting from exercise of stock options	3,382		3,382
Stock-based compensation	1,977		1,977
Common stock issued for acquisitions	10,100	3	10,097
Common stock issued for acquisitions, Shares		302
Dividends declared	(32,431)			(32,431)
Net income	46,119			46,119
Reclassification of unrealized loss on marketable securities, net of tax	196				196
Ending balance at Mar. 31, 2009	155,567	284	103,524	51,759	0
Ending balance, Shares at Mar. 31, 2009		28,447
Exercise of stock options	5,855	3	5,852
Exercise of stock options, Shares		238
Tax benefit resulting from exercise of stock options	1,576		1,576
Stock-based compensation	2,073		2,073
Stock-based compensation related to acquisitions	433		433
Common stock issued for acquisitions	8,815	2	8,813
Common stock issued for acquisitions, Shares		194
Dividends declared	(34,409)			(34,409)
Net income	48,379			48,379
Ending balance at Mar. 31, 2010	188,289	289	122,271	65,729	0
Ending balance, Shares at Mar. 31, 2010		28,879
Exercise of stock options	5,717	1	5,716
Exercise of stock options, Shares		155
Tax benefit resulting from exercise of stock options	1,524		1,524
Stock-based compensation	3,748		3,748
Dividends declared	(36,214)			(36,214)
Net income	61,606			61,606
Ending balance at Mar. 31, 2011	$ 224,670	$ 290	$ 133,259	$ 91,121	$ 0
Ending balance, Shares at Mar. 31, 2011		29,034