Fair Value Measurements - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Jan. 31, 2019	Oct. 31, 2018
Liabilities:
Debt conversion liability	$ 0	$ 164,212
Fair value, Measurements, Recurring
Assets:
Total assets measured at fair value	669,303	859,472
Liabilities:
Debt conversion liability		164,212
Total liabilities measured at fair value	20,571	178,343
Fair value, Measurements, Recurring | Cash equivalents
Assets:
Cash equivalents	550,108	650,609
Fair value, Measurements, Recurring | Short-term investments
Assets:
Short-term investments	119,143	148,981
Fair value, Measurements, Recurring | Prepaid expenses and other
Assets:
Prepaid expenses and other	52	133
Fair value, Measurements, Recurring | Long-term investments
Assets:
Long-term investments		58,970
Fair value, Measurements, Recurring | Other long-term assets
Assets:
Other long-term assets		779
Fair value, Measurements, Recurring | Accrued liabilities
Liabilities:
Accrued liabilities	9,078	3,231
Fair value, Measurements, Recurring | Debt conversion liability
Liabilities:
Debt conversion liability		164,212
Fair value, Measurements, Recurring | Other long-term obligations
Liabilities:
Other long-term obligations	11,493	10,900
Fair value, Measurements, Recurring | Level 1
Assets:
Total assets measured at fair value	530,110	590,684
Liabilities:
Debt conversion liability		0
Total liabilities measured at fair value	0	0
Fair value, Measurements, Recurring | Level 1 | Cash equivalents
Assets:
Cash equivalents	530,110	590,684
Fair value, Measurements, Recurring | Level 1 | Short-term investments
Assets:
Short-term investments	0	0
Fair value, Measurements, Recurring | Level 1 | Prepaid expenses and other
Assets:
Prepaid expenses and other	0	0
Fair value, Measurements, Recurring | Level 1 | Long-term investments
Assets:
Long-term investments		0
Fair value, Measurements, Recurring | Level 1 | Other long-term assets
Assets:
Other long-term assets		0
Fair value, Measurements, Recurring | Level 1 | Accrued liabilities
Liabilities:
Accrued liabilities	0	0
Fair value, Measurements, Recurring | Level 1 | Debt conversion liability
Liabilities:
Debt conversion liability		0
Fair value, Measurements, Recurring | Level 1 | Other long-term obligations
Liabilities:
Other long-term obligations	0	0
Fair value, Measurements, Recurring | Level 2
Assets:
Total assets measured at fair value	139,193	268,788
Liabilities:
Debt conversion liability		164,212
Total liabilities measured at fair value	9,671	167,443
Fair value, Measurements, Recurring | Level 2 | Cash equivalents
Assets:
Cash equivalents	19,998	59,925
Fair value, Measurements, Recurring | Level 2 | Short-term investments
Assets:
Short-term investments	119,143	148,981
Fair value, Measurements, Recurring | Level 2 | Prepaid expenses and other
Assets:
Prepaid expenses and other	52	133
Fair value, Measurements, Recurring | Level 2 | Long-term investments
Assets:
Long-term investments		58,970
Fair value, Measurements, Recurring | Level 2 | Other long-term assets
Assets:
Other long-term assets		779
Fair value, Measurements, Recurring | Level 2 | Accrued liabilities
Liabilities:
Accrued liabilities	1,587	3,231
Fair value, Measurements, Recurring | Level 2 | Debt conversion liability
Liabilities:
Debt conversion liability		164,212
Fair value, Measurements, Recurring | Level 2 | Other long-term obligations
Liabilities:
Other long-term obligations	8,084	0
Fair value, Measurements, Recurring | Level 3
Assets:
Total assets measured at fair value	0	0
Liabilities:
Debt conversion liability		0
Total liabilities measured at fair value	10,900	10,900
Fair value, Measurements, Recurring | Level 3 | Cash equivalents
Assets:
Cash equivalents	0	0
Fair value, Measurements, Recurring | Level 3 | Short-term investments
Assets:
Short-term investments	0	0
Fair value, Measurements, Recurring | Level 3 | Prepaid expenses and other
Assets:
Prepaid expenses and other	0	0
Fair value, Measurements, Recurring | Level 3 | Long-term investments
Assets:
Long-term investments		0
Fair value, Measurements, Recurring | Level 3 | Other long-term assets
Assets:
Other long-term assets		0
Fair value, Measurements, Recurring | Level 3 | Accrued liabilities
Liabilities:
Accrued liabilities	7,491	0
Fair value, Measurements, Recurring | Level 3 | Debt conversion liability
Liabilities:
Debt conversion liability		0
Fair value, Measurements, Recurring | Level 3 | Other long-term obligations
Liabilities:
Other long-term obligations	$ 3,409	$ 10,900