Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Topic 835
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-Section 45
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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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-Topic 825
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-Section 50
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- Definition

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

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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))
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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.

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Debt - Fair Value of Outstanding Debt (Details)	Jun. 30, 2018 EUR (€)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($)
7.456% Senior Notes Due 2018
Debt Instrument [Line Items]
Fair value of senior notes		$ 502,000,000		$ 516,000,000
Debt, interest rate (percentage)	7.456%	7.456%
Senior unsecured notes principal amount		$ 500,000,000
5.95% Senior Notes Due 2020
Debt Instrument [Line Items]
Fair value of senior notes		$ 790,000,000		810,000,000
Debt, interest rate (percentage)	5.95%	5.95%
Senior unsecured notes principal amount		$ 750,000,000
2.5% Senior Notes Due 2022
Debt Instrument [Line Items]
Fair value of senior notes	€ 688,000,000	$ 804,000,000	€ 690,000,000	828,000,000
Debt, interest rate (percentage)	2.50%	2.50%
Senior unsecured notes principal amount \| €	€ 650,000,000
4.5% Senior Notes Due 2024
Debt Instrument [Line Items]
Fair value of senior notes		$ 500,000,000		528,000,000
Debt, interest rate (percentage)	4.50%	4.50%
Senior unsecured notes principal amount		$ 500,000,000
5.0% Senior Notes Due 2026
Debt Instrument [Line Items]
Fair value of senior notes		$ 767,000,000		807,000,000
Debt, interest rate (percentage)	5.00%	5.00%
Senior unsecured notes principal amount		$ 750,000,000
3.8% senior notes due 2028
Debt Instrument [Line Items]
Fair value of senior notes		$ 920,000,000		$ 969,000,000
Debt, interest rate (percentage)	3.80%	3.80%
Senior unsecured notes principal amount		$ 1,000,000,000