Income Taxes (Summary Of Federal Income Tax Rate And Effective Income Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 7,021	$ (492)	$ (23,517)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	(181,047)	17,334	37,996
Effective Income Tax Rate Reconciliation, Transition Impact of U.S. Tax Act 2017, Amount	126,122	0	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	69,648	0	0
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	2,401	627	(82)
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount	(3,058)	(2,182)	(5,981)
Effective Income Tax Rate Reconciliation, Resolution of Uncertain Tax Positions, Amount	(4,646)	(3,840)	0
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(38,743)	(27,932)	(27,513)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Withholding, Amount	2,736	2,737	1,987
Effective Income Tax Rate Reconciliation, Excess Tax Benefits from Restricted Stock, Amount	(11,641)	0	0
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount	2,352	0	0
Effective Income Tax Rate Reconciliation, Permanent Domestic Items, Amount	5,408	6,030	2,886
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	116	73	1,497
Benefit from income taxes	$ (23,331)	$ (7,645)	$ (12,727)
Statutory federal income tax rate	25.00%	35.00%	35.00%
Change in valuation allowance	(632.00%)	(1233.00%)	(57.00%)
Transition impact of U.S. Tax Act	440.00%	0.00%	0.00%
Federal rate change	243.00%	0.00%	0.00%
State income taxes, net of federal tax benefit	8.00%	(45.00%)	0.00%
Federal and state research and development credits	(11.00%)	155.00%	9.00%
Resolution of uncertain tax positions	(16.00%)	273.00%	0.00%
Foreign rate differences	(135.00%)	1987.00%	41.00%
Foreign withholding tax	10.00%	(195.00%)	(3.00%)
Excess tax benefits from restricted stock	(41.00%)	0.00%	0.00%
Audits and settlements	8.00%	0.00%	0.00%
U.S. permanent items	19.00%	(429.00%)	(4.00%)
Other, net	1.00%	(4.00%)	(2.00%)
Effective income tax rate	(81.00%)	544.00%	19.00%

Effective Income Tax Rate Reconciliation, Excess Tax Benefits from Restricted Stock, Amount

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