Fair Value Measurements - Narrative (Details) $ / shares in Units, $ in Thousands	Oct. 31, 2020 USD ($) $ / shares
Debt Instrument [Line Items]
Closing price of common stock (in dollars per share) \| $ / shares	$ 209.83
Convertible Senior Notes Due 2023 \| Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 40,246
Convertible Senior Notes Due 2025 \| Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	1,060,000
Convertible Senior Notes Due 2026 \| Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 1,150,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant