Debt (Commercial Paper) (Details) - Commercial paper € in Millions, $ in Millions	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)
U.S. dollar
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity \| $	$ 1,500.0
Weighted average interest rate	1.78%	1.78%
Euro
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity \| €		€ 1,000.0
Weighted average interest rate	(0.27%)	(0.27%)

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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