Stock-Based Compensation - Overview (Details) - shares		3 Months Ended
	Dec. 05, 2017	Oct. 31, 2017	Jul. 31, 2017
Stock options
Stock-Based Awards Outstanding By Award Type
Number of stock-based option awards outstanding at period end (in shares)		1,814,835	1,855,875
2000 Stock Incentive Plan
2000 Stock Incentive Plan
Aggregate maximum number of shares of common stock which may be issued under stock option plan (in shares)		9,462,500
Aggregate net number of stock-based awards granted (in shares)		8,100,581
Aggregate number of stock based awards expired and canceled (in shares)		3,826,857
Aggregate number of stock-based awards exercised or settled (in shares)		5,310,196
Stock-Based Awards Outstanding By Award Type
Number of total stock-based awards outstanding (in shares)		2,790,385
2000 Stock Incentive Plan | Stock options
2000 Stock Incentive Plan
Maximum term for grants of incentive and non-qualified stock-based awards, excluding incentive stock-based awards granted to stockholders who own more than 10% of the voting power		10 years
Percentage of a stockholder's voting power that limits the contractual term of an incentive stock-based award		10.00%
Maximum term for incentive stock-based awards granted to stockholders who own more than 10% of the voting power		5 years
Stock-Based Awards Outstanding By Award Type
Number of stock-based option awards outstanding at period end (in shares)		1,814,835
2000 Stock Incentive Plan | Performance shares
Stock-Based Awards Outstanding By Award Type
Number of stock-based non-option awards outstanding at period end (in shares)		277,881
2000 Stock Incentive Plan | RSUs and restricted stock
Stock-Based Awards Outstanding By Award Type
Number of stock-based non-option awards outstanding at period end (in shares)		430,063
2000 Stock Incentive Plan | Share units
Stock-Based Awards Outstanding By Award Type
Number of stock-based non-option awards outstanding at period end (in shares)		267,606
2001 Employee Stock Purchase Plan | Employee Stock Purchase Plan - ESPP
2000 Stock Incentive Plan
Aggregate maximum number of shares of common stock which may be issued under stock option plan (in shares)		800,000
2001 Employee Stock Purchase Plan
Discount rate from market value, on purchase date, offered to employees participating in the Employee Stock Purchase Plan (ESPP)		85.00%
Total number of shares of common stock issued to employees under employee stock purchase plan and through the end of the reporting period (in shares)		710,413
Subsequent Event | 2000 Stock Incentive Plan
2000 Stock Incentive Plan
Aggregate maximum number of shares of common stock which may be issued under stock option plan (in shares)	10,362,500
Number of additional shares authorized (in shares)	900,000