Segment Information (Details) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended	29 Months Ended
	Mar. 31, 2018 USD ($) Segment	Dec. 30, 2017 Segment	Apr. 01, 2017 USD ($)	Mar. 31, 2018 USD ($)	Apr. 01, 2017 USD ($)	Sep. 30, 2017 Segment	Mar. 31, 2018 USD ($)
Number of operating segments | Segment	2	2				3
Number of reportable segments | Segment	2					3
Revenue	$ 307,883		$ 280,040	$ 614,527	$ 566,367
Operating Costs	83,631		81,830	166,589	163,945
Gross margin	224,252		198,210	447,938	402,422
Sales and marketing	98,330		87,777	197,645	178,467
General and administrative	33,353		36,800	68,357	73,495
Restructuring and other charges, net	114		464	219	6,749		$ 84,700
Amortization of acquired intangible assets	7,895		7,946	15,716	16,013
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)
Operating Segments
Revenue	307,883		280,040	614,527	566,367
Operating Costs	133,215		126,101	267,684	253,964
Gross margin	174,668		153,939	346,843	312,403
Operating Segments | Software Products
Revenue	262,453		234,870	527,643	475,089
Operating Costs	97,306		88,832	196,995	178,871
Gross margin	165,147		146,038	330,648	296,218
Operating Segments | Professional Services
Revenue	45,430		45,170	86,884	91,278
Operating Costs	35,909		37,269	70,689	75,093
Gross margin	9,521		7,901	16,195	16,185
Unallocated
Sales and marketing	93,292		83,647	187,728	170,716
General and administrative	27,382		25,957	54,814	54,007
Restructuring and other charges, net	114		464	219	6,749
Amortization of acquired intangible assets	14,451		14,335	28,947	28,790
Stock-based compensation	17,026		21,577	35,357	39,565
Other unallocated operating expenses	$ 37		$ 446	$ (60)	$ 502