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Subsequent Events (Details) - $ / shares shares in Millions	2 Months Ended	12 Months Ended
	Feb. 21, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2018
Common Stock
Subsequent Event [Line Items]
Shares repurchased (in shares)		2.4	0.2	1.7
Average price (in usd per share)		$ 173.19	$ 161.16	$ 209.39
Subsequent Event | January 2018 Plan
Subsequent Event [Line Items]
Shares repurchased (in shares)	0.7
Average price (in usd per share)	$ 193.18
Subsequent Event | Common Stock
Subsequent Event [Line Items]
Stock repurchase plan, number of remaining shares to be repurchased (in shares)					5.0
Subsequent Event | Common Stock | January 2018 Plan
Subsequent Event [Line Items]
Stock repurchase program, number of shares authorized (in shares)					3.4

X

- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

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X

- Definition

The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

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X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

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X

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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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X

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

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