Earnings Per Share Calculation - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017	Oct. 31, 2017
Numerator
Net income (loss)	$ 50,840	$ 60,010	$ (408,667)	$ 101,897
Net income (loss) used to calculate Diluted EPS	$ 53,928	$ 67,151	$ (408,667)	$ 113,990
Denominator
Basic weighted average shares outstanding (in shares)	143,400	142,464	143,766	141,631
Add: Shares underlying outstanding stock options and restricted stock units and issuable under employee stock purchase plan (in shares)	1,330	1,386	0	1,401
Dilutive weighted average shares outstanding (in shares)	159,998	172,112	143,766	164,431
EPS
Basic EPS (in dollars per share)	$ 0.35	$ 0.42	$ (2.84)	$ 0.72
Diluted EPS (in dollars per share)	$ 0.34	$ 0.39	$ (2.84)	$ 0.69
0.875% Convertible Senior Notes due June 15, 2017
Numerator
Add: Interest expense associated with convertible senior notes	$ 0	$ 246	$ 0	$ 1,343
Denominator
Add: Shares underlying convertible senior notes (in shares)	0	1,708	0	4,043
EPS
Interest rate on convertible notes (as a percent)		0.875%		0.875%	0.875%
3.75% Convertible Senior Notes due October 15, 2018 (New)
Denominator
Add: Shares underlying convertible senior notes (in shares)	3,032	0	0	0
EPS
Interest rate on convertible notes (as a percent)	3.75%		3.75%
3.75% Convertible Senior Notes due October 15, 2018 (Original)
Numerator
Add: Interest expense associated with convertible senior notes	$ 464	$ 3,572	$ 0	$ 10,750
Denominator
Add: Shares underlying convertible senior notes (in shares)	3,038	17,356	0	17,356
EPS
Interest rate on convertible notes (as a percent)	3.75%		3.75%
4.0% Convertible Senior Notes due December 15, 2020
Numerator
Add: Interest expense associated with convertible senior notes	$ 2,624	$ 3,323	$ 0	$ 0
Denominator
Add: Shares underlying convertible senior notes (in shares)	9,198	9,198	0	0
EPS
Interest rate on convertible notes (as a percent)	4.00%		4.00%