Income Taxes - Summary of Changes in Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance, beginning of year	$ 221	$ 202
Increase based on tax positions related to current year	21	17
(Decrease) increase based on tax positions of prior years	(52)	53
Increase related to acquisitions	44
Settlements	(2)	(15)
Statute expirations	(8)	(20)
Foreign currency translation	(4)	(16)
Balance, ending of year	$ 220	$ 221

Unrecognized tax benefits increase decrease resulting from foreign currency translation.

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- Definition

Unrecognized tax benefits increase decreases resulting from prior period tax positions.

+ References

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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=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from acquisitions.

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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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