Goodwill - Summary of Goodwill Identified by Segment (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Beginning balance	$ 311	$ 205
Additions	2	117
Currency translation adjustments and other	15	(11)
Goodwill, Ending balance	328	311
United States [Member]
Goodwill [Line Items]
Goodwill, Beginning balance	117
Additions	2	117
Goodwill, Ending balance	119	117
Canada (Member)
Goodwill [Line Items]
Goodwill, Beginning balance	91	88
Currency translation adjustments and other	7	3
Goodwill, Ending balance	98	91
International [Member]
Goodwill [Line Items]
Goodwill, Beginning balance	103	117
Currency translation adjustments and other	8	(14)
Goodwill, Ending balance	$ 111	$ 103

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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