Earnings Per Share - Narratives (Details) - Convertible Notes, due 2024 - Convertible Debt	Oct. 31, 2017 $ / shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Debt instrument, conversion price (usd per share)	$ 58.725
Maximum
Antidilutive Securities Excluded from Computation of Earnings Per Share
Debt instrument, conversion price (usd per share)	$ 71.775

The price per share of the conversion feature embedded in the debt instrument.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466204&loc=SL6031898-161870

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant