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, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Numerator
Net income (loss)	$ 86,749	$ 50,840	$ 173,103	$ (408,667)
Net income (loss) used to calculate Diluted EPS	$ 86,749	$ 53,928	$ 173,103	$ (408,667)
Denominator
Basic weighted average shares outstanding (in shares)	155,488	143,400	156,013	143,766
Add: Shares underlying outstanding stock options and restricted stock units and issuable under employee stock purchase plan (in shares)	1,967	1,330	1,936	0
Dilutive weighted average shares outstanding (in shares)	157,455	159,998	157,949	143,766
EPS
Basic EPS (in dollars per share)	$ 0.56	$ 0.35	$ 1.11	$ (2.84)
Diluted EPS (in dollars per share)	$ 0.55	$ 0.34	$ 1.10	$ (2.84)
3.75% Convertible Senior Notes due 2018 (New)
Denominator
Add: Shares underlying Convertible Senior Notes (in shares)	0	3,032	0	0
EPS
Interest rate on convertible notes (as a percent)	3.75%		3.75%
3.75% Convertible Senior Notes due 2018 (Original)
Numerator
Add: Interest expense associated with Convertible Senior Notes	$ 0	$ 464	$ 0	$ 0
Denominator
Add: Shares underlying Convertible Senior Notes (in shares)	0	3,038	0	0
EPS
Interest rate on convertible notes (as a percent)	3.75%		3.75%
4.0% Convertible Senior Notes due 2020
Numerator
Add: Interest expense associated with Convertible Senior Notes	$ 0	$ 2,624	$ 0	$ 0
Denominator
Add: Shares underlying Convertible Senior Notes (in shares)	0	9,198	0	0
EPS
Interest rate on convertible notes (as a percent)	4.00%		4.00%