Disposition of Business (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Feb. 01, 2019	Nov. 07, 2018	Sep. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Document Period End Date			Mar. 31, 2019
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net							$ 30,959
Provision for Income Taxes, Discontinued Operations	$ (4,363)	$ 551	$ (2,688)	$ 999
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	98,081	3,088	99,472	8,851
Depreciation, Discontinued Operations	97	333	391	750
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	1,643	5,995	6,569	12,060
Stock Compensation Expense, Discontinued Operations	5,001	2,007	7,103	3,768
Disposal Group, Including Discontinued Operation, Prepaid and Other Assets							3,443
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment							2,442
Disposal Group, Including Discontinued Operation, Goodwill							257,352
Disposal Group, Including Discontinued Operation, Intangible Assets							99,507
Disposal Group, Including Discontinued Operation, Other Assets							196
Disposal Group, Including Discontinued Operation, Assets							393,899
Disposal Group, Including Discontinued Operation, Accounts Payable							3,604
Disposal Group, Including Discontinued Operation, Accrued Liabilities							12,304
Disposal Group, Including Discontinued Operation, Deferred Revenue							107,965
Disposal Group, Including Discontinued Operation, Revenue	15,435	48,031	67,430	102,452
Disposal Group, Including Discontinued Operation, Consideration					$ 404,000	$ 400,000
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	4,942	11,968	16,946	24,924
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	(8,653)	3,639	(5,587)	9,850
Disposal Group, Including Discontinued Operation, Other Liabilities							2,658
Disposal Group, Including Discontinued Operation, Liabilities							$ 126,531
Gain (Loss) on Disposition of Business	102,371	0	102,371	0
Restructuring Charges [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Expense	4,791	67	13,251	1,299
Other Expenses	0	162	0	162
Acquisition-related Costs [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Expense	0	0	(386)	0
Other Expense [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Expense	1,305	4,273	5,219	8,496
General and Administrative Expense
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Expense	766	1,105	1,997	2,224
Sales and marketing
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Expense	10,243	19,330	28,433	40,730
Research and Development
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Operating Expense	$ 2,041	$ 7,487	$ 7,557	$ 14,767