Debt - Schedule of Debt and Capital Lease Obligations (Parenthetical) (Details)	12 Months Ended
Dec. 31, 2017
Debt Instrument [Line Items]
Debt instrument, interest rate	4.70%
4.7% senior notes due 2025
Debt Instrument [Line Items]
Debt instrument, interest rate	4.70%
Debt instrument, maturity year	2025
3.95% senior notes due 2027
Debt Instrument [Line Items]
Debt instrument, interest rate	3.95%
Debt instrument, maturity year	2027
Senior unsecured credit facility - due 2021
Debt Instrument [Line Items]
Debt instrument, maturity year	2021

Contractual interest rate for funds borrowed, under the debt agreement.

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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant