Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance, shares at Sep. 30, 2015		113,745
Beginning Balance, value at Sep. 30, 2015	$ 860,171	$ 1,137	$ 1,553,390	$ (602,614)	$ (91,742)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for employee stock-based awards, shares		1,820
Common stock issued for employee stock-based awards, value	21	$ 18	3
Shares surrendered by employees to pay taxes related to stock-based awards, shares		(597)
Shares surrendered by employees to pay taxes related to stock-based awards, value	(20,939)	$ (5)	(20,934)
Compensation expense from stock-based awards	65,996		65,996
Excess tax benefits from stock-based awards	93		93
Net income (loss)	(54,465)			(54,465)
Unrealized loss on hedging instruments, net of tax	(1,244)				(1,244)
Foreign currency translation adjustment	408				408
Unrealized loss on available-for-sale securities, net of tax	(122)				(122)
Change in pension benefits, net of tax	(7,253)				(7,253)
Ending Balance, shares at Sep. 30, 2016		114,968
Ending Balance, value at Sep. 30, 2016	842,666	$ 1,150	1,598,548	(657,079)	(99,953)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for employee stock-based awards, shares		1,586
Common stock issued for employee stock-based awards, value	0	$ 15	(15)
Shares surrendered by employees to pay taxes related to stock-based awards, shares		(544)
Shares surrendered by employees to pay taxes related to stock-based awards, value	(26,654)	$ (5)	(26,649)
Common stock issued for employee stock purchase plan, shares		269
Common stock issued for employee stock purchase plan, value	10,778	$ 3	10,775
Compensation expense from stock-based awards	76,708		76,708
Excess tax benefits from stock-based awards	644		644
Net income (loss)	6,239			6,239
Repurchases of common stock, shares		(946)
Repurchases of common stock, value	(50,991)	$ (10)	(50,981)
Unrealized loss on hedging instruments, net of tax	(299)				(299)
Foreign currency translation adjustment	16,593				16,593
Unrealized loss on available-for-sale securities, net of tax	(22)				(22)
Change in pension benefits, net of tax	$ 9,774				9,774
Ending Balance, shares at Sep. 30, 2017	115,333	115,333
Ending Balance, value at Sep. 30, 2017	$ 885,436	$ 1,153	1,609,030	(650,840)	(73,907)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-09 [Member]	125		681	(556)
Common stock issued for employee stock-based awards, shares		1,830
Common stock issued for employee stock-based awards, value	0	$ 18	(18)
Shares surrendered by employees to pay taxes related to stock-based awards, shares		(664)
Shares surrendered by employees to pay taxes related to stock-based awards, value	(45,374)	$ (6)	(45,368)
Stock Issued During Period, Shares, New Issues		10,582
Stock Issued During Period, Value, New Issues	995,500	$ 106	995,394
Common stock issued for employee stock purchase plan, shares		292
Common stock issued for employee stock purchase plan, value	15,654	$ 2	15,652
Compensation expense from stock-based awards	82,939		82,939
Net income (loss)	51,987			51,987
Repurchases of common stock, shares		(9,392)
Repurchases of common stock, value	(1,100,000)	$ (93)	(1,099,907)
Unrealized loss on hedging instruments, net of tax	1,928				1,928
Foreign currency translation adjustment	(11,767)				(11,767)
Unrealized loss on available-for-sale securities, net of tax	(269)				(269)
Change in pension benefits, net of tax	$ (1,570)				(1,570)
Ending Balance, shares at Sep. 30, 2018	117,981	117,981
Ending Balance, value at Sep. 30, 2018	$ 874,589	$ 1,180	$ 1,558,403	$ (599,409)	$ (85,585)