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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

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Debt (Details) - Repayment - USD ($)		9 Months Ended
Debt (Details) - Repayment - USD ($)	May 15, 2018	Sep. 30, 2018	Sep. 30, 2017
Debt Instrument
Debt, principal amount repaid		$ 600,000,000	$ 207,000,000
Senior Notes [Member] \| 5.80% Senior Notes due May 15, 2018 [Member]
Debt Instrument
Debt, principal amount repaid	$ 500,000,000
Interest rate (percent)	5.80%