Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2013
Quarterly Financial Data (Unaudited)
Total revenue	$ 114,186	$ 111,299	$ 107,790	$ 107,126	$ 101,532	$ 103,587	$ 98,769	$ 87,565	$ 440,401	$ 391,453	$ 311,387
Gross profit	101,565	98,990	95,525	94,745	88,653	88,299	86,326	75,487	390,825	338,765	261,039
Income from operations	46,906	41,731	46,521	44,634	37,361	31,402	36,112	24,849	179,792	129,724	55,600
Net income	$ 30,806	$ 28,170	$ 30,464	$ 28,967	$ 26,678	$ 20,843	$ 23,263	$ 14,999	$ 118,407	$ 85,783	$ 45,262
Net income per common share:
Basic (in dollars per share)	$ 0.36	$ 0.32	$ 0.34	$ 0.32	$ 0.29	$ 0.23	$ 0.25	$ 0.16	$ 1.34	$ 0.93	$ 0.48
Diluted (in dollars per share)	$ 0.36	$ 0.32	$ 0.34	$ 0.32	$ 0.29	$ 0.22	$ 0.25	$ 0.16	$ 1.33	$ 0.92	$ 0.47
Weighted average shares outstanding:
Basic (in shares)	85,056	87,355	89,942	91,183	91,916	92,414	92,839	93,410	88,398	92,648	93,586
Diluted (in shares)	85,585	87,853	90,471	91,891	92,710	93,365	93,816	94,522	89,016	93,665	95,410