Net Loss Per Share (Schedule of Antidilutive Securities Excluded from Computation) (Details) - shares shares in Millions	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	37.4	27.1
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	13.1	6.4
Warrants related to the issuance of convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	13.1	9.6
RSUs and PSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	8.3	7.7
Options to purchase common stock, including PSOs
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	2.8	3.2
Restricted stock awards and performance-based stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	0.0	0.1
ESPP shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities (in shares)	0.1	0.1