Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Mar. 31, 2018	Apr. 01, 2017
Revenues [Abstract]
Subscription	$ 112,931	$ 65,780	$ 212,939	$ 120,142
Support	126,683	141,718	257,880	293,196
Total recurring revenue	239,614	207,498	470,819	413,338
Perpetual license	22,839	27,372	56,824	61,751
Total subscription, support and license revenue	262,453	234,870	527,643	475,089
Professional services	45,430	45,170	86,884	91,278
Total revenue	307,883	280,040	614,527	566,367
Cost of revenue:
Cost of license and subscription revenue	23,119	20,555	47,495	40,685
Cost of support revenue	23,030	22,576	45,230	45,393
Total cost of software revenue	46,149	43,131	92,725	86,078
Cost of professional services revenue	37,482	38,699	73,864	77,867
Total cost of revenue	83,631	81,830	166,589	163,945
Gross margin	224,252	198,210	447,938	402,422
Operating expenses:
Sales and marketing	98,330	87,777	197,645	178,467
Research and development	62,194	57,710	126,163	115,624
General and administrative	33,353	36,800	68,357	73,495
Amortization of acquired intangible assets	7,895	7,946	15,716	16,013
Restructuring and other charges, net	114	464	219	6,749
Total operating expenses	201,886	190,697	408,100	390,348
Operating income	22,366	7,513	39,838	12,074
Interest expense	(10,379)	(11,725)	(20,426)	(22,040)
Interest income and other expense, net	(441)	3,156	(1,395)	2,407
Income (loss) before income taxes	11,546	(1,056)	18,017	(7,559)
Provision (benefit) for income taxes	3,624	48	(3,782)	2,686
Net income (loss)	$ 7,922	$ (1,104)	$ 21,799	$ (10,245)
Earnings(loss) per share—Basic (in USD per share)	$ 0.07	$ (0.01)	$ 0.19	$ (0.09)
Earnings(loss) per share—Diluted (in USD per share)	$ 0.07	$ (0.01)	$ 0.19	$ (0.09)
Weighted average shares outstanding—Basic (in shares)	116,241	115,709	115,986	115,498
Weighted average shares outstanding—Diluted (in shares)	117,905	115,709	117,780	115,498