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Earnings Per Share (Narrative) (Details) - January 2016 Share Repurchase Program - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, shares acquired (in shares)	0	1,994,632
Stock repurchase program, average price per share (in dollars per share)		$ 72.39

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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

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- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

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Number of shares that have been repurchased during the period and are being held in treasury.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

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-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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