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, 2014		115,025
Beginning Balance, value at Sep. 30, 2014	$ 853,889	$ 1,150	$ 1,597,277	$ (650,171)	$ (94,367)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for employee stock-based awards, shares		2,212
Common stock issued for employee stock-based awards, value	41	$ 22	19
Shares surrendered by employees to pay taxes related to stock-based awards, shares		(764)
Shares surrendered by employees to pay taxes related to stock-based awards, value	(29,207)	$ (8)	(29,199)
Compensation expense from stock-based awards	50,182		50,182
Excess tax benefits from stock-based awards	24		24
Net income (loss)	47,557			47,557
Repurchases of common stock, shares		(2,728)
Repurchases of common stock, value	(64,940)	$ (27)	(64,913)
Unrealized loss on hedging instruments, net of tax	0
Foreign currency translation adjustment	(47,177)				(47,177)
Unrealized loss on available-for-sale securities, net of tax	0
Change in pension benefits, net of tax	49,802				49,802
Ending Balance, shares at Sep. 30, 2015		113,745
Ending 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	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)