Capital Actions (Capital Actions - Additional Information)(Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016
Capital Actions
Shares acquired for treasury	$ 342	$ 265
April 27, 2017 ASR \| March 2016 Repurchase Program
Capital Actions
Redemption Date	May 01, 2017
Shares acquired for treasury	$ 342
Shares repurchased on repurchase date	11,641,971
Shares received from forward contract settlement	2,248,250
Total shares repurchased	13,890,221
Settlement date	Jul. 31, 2017
December 16, 2016 ASR \| March 2016 Repurchase Program
Capital Actions
Redemption Date	Dec. 20, 2016
Shares acquired for treasury	$ 155
Shares repurchased on repurchase date	4,843,750
Shares received from forward contract settlement	1,044,362
Total shares repurchased	5,888,112
Settlement date	Feb. 06, 2017

Common stock repurchased in an ASR transaction

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- Definition

Initial redemption date for share repurchase transaction

+ References

No definition available.

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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

Settlement date of the forward contract indexed to issuer's equity, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=6445032&loc=d3e90205-114008

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- Definition

Additional shared included in the calculation of diluted EPS as a result of the potentially dilutive effect of equity forward arrangements using the reverse treasury stock method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2366-109256

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- Definition

Number of stock bought back by the entity at the exercise price or redemption price.

+ References

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- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

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-Name Accounting Standards Codification
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