Fair Value Measurements (Details) - USD ($) $ in Millions | 12 Months Ended | |
Jul. 31, 2017 | Oct. 31, 2017 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | $ 0 | $ 255.1 |
Short-term investments | 630.7 | 660.6 |
Prepaid expenses and other current assets | 0 | 0.2 |
Long-term investments | 789.3 | 777.4 |
Total assets measured at fair value | 1,420 | 1,693.3 |
Accrued and other liabilities | 0 | 1.8 |
Total liabilities measured at fair value | 0 | 1.8 |
Impairment of property and equipment | 20.9 | |
Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 250.1 |
Short-term investments | 0 | 0 |
Prepaid expenses and other current assets | 0 | 0 |
Long-term investments | 0 | 0 |
Total assets measured at fair value | 0 | 250.1 |
Accrued and other liabilities | 0 | 0 |
Total liabilities measured at fair value | 0 | 0 |
Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 5 |
Short-term investments | 630.7 | 660.6 |
Prepaid expenses and other current assets | 0 | 0.2 |
Long-term investments | 789.3 | 777.4 |
Total assets measured at fair value | 1,420 | 1,443.2 |
Accrued and other liabilities | 0 | 1.8 |
Total liabilities measured at fair value | 0 | 1.8 |
Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 0 |
Short-term investments | 0 | 0 |
Prepaid expenses and other current assets | 0 | 0 |
Long-term investments | 0 | 0 |
Total assets measured at fair value | 0 | 0 |
Accrued and other liabilities | 0 | 0 |
Total liabilities measured at fair value | 0 | 0 |
Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 250.1 |
Money market funds | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 250.1 |
Money market funds | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 0 |
Money market funds | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 0 |
U.S. government and agency securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 5 |
Short-term investments | 471.3 | 490.3 |
Long-term investments | 597.4 | 587.9 |
U.S. government and agency securities | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 0 |
Short-term investments | 0 | 0 |
Long-term investments | 0 | 0 |
U.S. government and agency securities | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 5 |
Short-term investments | 471.3 | 490.3 |
Long-term investments | 597.4 | 587.9 |
U.S. government and agency securities | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Cash equivalents | 0 | 0 |
Short-term investments | 0 | 0 |
Long-term investments | 0 | 0 |
Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Short-term investments | 159.4 | 170.3 |
Long-term investments | 186.5 | 184.1 |
Corporate debt securities | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Short-term investments | 0 | 0 |
Long-term investments | 0 | 0 |
Corporate debt securities | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Short-term investments | 159.4 | 170.3 |
Long-term investments | 186.5 | 184.1 |
Corporate debt securities | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Short-term investments | 0 | 0 |
Long-term investments | 0 | 0 |
Foreign currency forward contracts | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Prepaid expenses and other current assets | 0 | 0.2 |
Accrued and other liabilities | 0 | 1.8 |
Foreign currency forward contracts | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Prepaid expenses and other current assets | 0 | 0 |
Accrued and other liabilities | 0 | 0 |
Foreign currency forward contracts | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Prepaid expenses and other current assets | 0 | 0.2 |
Accrued and other liabilities | 0 | 1.8 |
Foreign currency forward contracts | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Prepaid expenses and other current assets | 0 | 0 |
Accrued and other liabilities | 0 | 0 |
Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Long-term investments | 5.4 | 5.4 |
Certificates of deposit | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Long-term investments | 0 | 0 |
Certificates of deposit | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Long-term investments | 5.4 | 5.4 |
Certificates of deposit | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Long-term investments | 0 | $ 0 |
Fair Value, Measurements, Nonrecurring | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis | | |
Leasehold improvements and other long-lived assets related to previous corporate headquarters | $ 4.2 | |