Contingencies - Narrative (Details) - USD ($)	9 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Estimate of possible loss	$ 13,000,000
Unrecognized tax benefits	93,000,000	$ 94,000,000
Minimum
Loss Contingencies [Line Items]
Estimate of possible loss	0
Maximum
Loss Contingencies [Line Items]
Estimate of possible loss	45,000,000
Shareholder Litigation
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party	4,900,000
Legal Reserve \| Invoicing Matter
Loss Contingencies [Line Items]
Estimate of possible loss	$ 360,000,000

Amount awarded to other party in judgment or settlement of litigation.

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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.

+ Details

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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