Derivative Financial Instruments and Fair Value Measurements - Narrative (Details)	9 Months Ended
Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Minimum outstanding purchase commitment range	1 month
Maximum outstanding purchase commitment range	1 year

Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration