Consolidated Income Statements (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended
	Aug. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Net revenues
Products		$ 212,291	$ 196,746	$ 185,107	$ 204,712	$ 209,718	$ 207,118	$ 205,165	$ 196,554	$ 798,856	$ 818,555	$ 721,975
Services		183,038	173,556	165,125	160,739	152,841	145,516	134,457	125,878	682,458	558,692	429,859
Total		395,329	370,302	350,232	365,451	362,559	352,634	339,622	322,432	1,481,314	1,377,247	1,151,834
Cost of net revenues
Products		35,151	32,350	29,773	31,792	35,752	34,482	33,668	33,200	129,066	137,102	129,325
Services		31,792	32,567	30,529	29,093	26,929	25,805	23,926	22,406	123,981	99,066	78,679
Total		66,943	64,917	60,302	60,885	62,681	60,287	57,594	55,606	253,047	236,168	208,004
Gross profit		328,386	305,385	289,930	304,566	299,878	292,347	282,028	266,826	1,228,267	1,141,079	943,830
Operating expenses
Sales and marketing		119,836	121,906	119,031	122,268	116,298	112,064	110,995	106,238	483,041	445,595	370,735
Research and development		54,464	54,075	52,534	48,541	47,731	46,985	43,568	39,122	209,614	177,406	138,910
General and administrative		26,512	25,327	25,889	24,673	24,015	23,298	22,785	21,677	102,401	91,775	83,523
Loss on facility sublease	2,393	2,393	0	0	0	0	0	0	0	2,393	0	0
Total		203,205	201,308	197,454	195,482	188,044	182,347	177,348	167,037	797,449	714,776	593,168
Income from operations		125,181	104,077	92,476	109,084	111,834	110,000	104,680	99,789	430,818	426,303	350,662
Other income, net		732	2,874	2,118	1,550	909	1,713	1,428	1,861	7,274	5,911	10,089
Income before income taxes		125,913	106,951	94,594	110,634	112,743	111,713	106,108	101,650	438,092	432,214	360,751
Provision for income taxes		49,682	38,773	31,182	41,141	45,026	39,377	37,467	35,158	160,778	157,028	119,354
Net income		$ 76,231	$ 68,178	$ 63,412	$ 69,493	$ 67,717	$ 72,336	$ 68,641	$ 66,492	$ 277,314	$ 275,186	$ 241,397
Net income per share - basic (USD per share)		$ 0.97	$ 0.87	$ 0.81	$ 0.88	$ 0.86	$ 0.91	$ 0.87	$ 0.84	$ 3.53	$ 3.48	$ 2.99
Weighted average shares - basic (shares)		78,353	78,516	78,601	78,789	78,980	79,135	79,156	79,272	78,565	79,135	80,658
Net income per share - diluted (USD per share)		$ 0.97	$ 0.86	$ 0.80	$ 0.88	$ 0.85	$ 0.91	$ 0.86	$ 0.83	$ 3.50	$ 3.45	$ 2.96
Weighted average shares - diluted (shares)		78,674	78,864	79,114	79,278	79,425	79,655	79,775	79,822	79,136	79,780	81,482