Business Acquisitions Pro Forma (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2010
Business Acquisition [Line Items]
Revenue	$ 266,609	$ 256,304	$ 255,858	$ 248,338	$ 249,255	$ 240,185	$ 242,635	$ 234,822	$ 1,027,109	$ 966,897	$ 836,586
Revenue Pro Forma											910,218
Gross Profit	108,512	103,383	107,409	104,426	104,192	95,290	102,819	97,033	423,730	399,334	345,120
Gross Profit Pro Forma											381,160
Net Income	43,327	36,657	38,525	36,475	36,574	33,081	36,045	31,771	154,984	137,471	117,870
Net income Pro Forma											$ 122,435
Diluted earnings per share	$ 0.50	$ 0.42	$ 0.44	$ 0.42	$ 0.42	$ 0.38	$ 0.42	$ 0.37	$ 1.78	$ 1.59	$ 1.38
Diluted earnings per share Pro Forma											$ 1.43
Diluted weighted average shares outstanding	87,051	87,592	87,371	87,134	87,090	86,972	86,523	86,147	87,287	86,687	85,381
Diluted weighted average shares outstanding Pro Forma											85,381
Basic earnings per share	$ 0.50	$ 0.42	$ 0.45	$ 0.42	$ 0.42	$ 0.38	$ 0.42	$ 0.37	$ 1.79	$ 1.60	$ 1.39
Basic earnings per share Pro Forma											$ 1.45
Basic weighted average shares outstanding	86,595	86,824	86,572	86,403	86,335	86,218	85,770	85,469	86,599	85,948	84,558
Basic weighted average shares outstanding Pro Forma											84,558