Segment and Geographic Information (Revenue And Operating Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Revenue	$ 1,255,631	$ 1,241,824	$ 1,164,039
Cost of revenue	325,378	326,502	328,502
Gross margin	930,253	915,322	835,537
Sales and marketing	417,449	414,764	372,702
General and administrative	127,919	143,045	144,991
Amortization of acquired intangible assets	23,841	31,350	32,108
Restructuring and other charges, net	51,100	(1,003)	7,942
Operating income	63,042	72,613	41,766
Interest expense	(43,047)	(41,673)	(42,400)
Other income (expense), net	305	(2,284)	(772)
Income before income taxes	20,300	28,656	(1,406)
Depreciation and amortization	77,824	87,408	86,742
Operating Segments [Member]
Revenue	1,255,631	1,241,824	1,164,039
Cost of revenue	511,310	524,953	511,767
Gross margin	744,321	716,871	652,272
Operating Segments [Member] | Software Products [Member]
Revenue	1,088,100	1,088,487	987,316
Cost of revenue	377,464	387,989	366,716
Gross margin	710,636	700,498	620,600
Depreciation and amortization	4,600	5,100	5,000
Operating Segments [Member] | Professional Services [Member]
Revenue	167,531	153,337	176,723
Cost of revenue	133,846	136,964	145,051
Gross margin	33,685	16,373	31,672
Depreciation and amortization	1,400	1,600	1,800
Unallocated [Member]
Sales and marketing	385,423	389,871	357,329
General and administrative	104,393	108,159	108,363
Amortization of acquired intangible assets	51,147	58,056	58,729
Restructuring and other charges, net	51,114	3,764	7,942
Stock-based compensation	86,400	82,939	76,708
Other unallocated operating expenses (3)	2,802	1,469	1,435
Operating income	63,042	72,613	41,766
Depreciation and amortization	20,600	22,700	21,200
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue	1,311,494	$ 1,241,824	$ 1,164,039
Cost of revenue	318,154
Gross margin	993,340
Sales and marketing	441,958
General and administrative	127,919
Amortization of acquired intangible assets	23,841
Operating income	101,620
Interest expense	(43,047)
Other income (expense), net	131
Income before income taxes	58,704
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments [Member]
Revenue	1,311,494
Cost of revenue	504,086
Gross margin	807,408
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments [Member] | Software Products [Member]
Revenue	1,150,818
Cost of revenue	375,268
Gross margin	775,550
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments [Member] | Professional Services [Member]
Revenue	160,676
Cost of revenue	128,818
Gross margin	31,858
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Unallocated [Member]
Sales and marketing	409,932
General and administrative	104,393
Amortization of acquired intangible assets	51,147
Restructuring and other charges, net	51,114
Stock-based compensation	86,400
Other unallocated operating expenses (3)	2,802
Operating income	$ 101,620