Commitments and Contingencies - Future Minimum Operating Lease Payments and Committed Subleases Under Non-cancelable Leases (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Operating lease obligations - Total Amounts	$ 81
Operating lease obligations - 2018	27
Operating lease obligations - 2019	20
Operating lease obligations - 2020	16
Operating lease obligations - 2021	8
Operating lease obligations - 2022	10
Sublease rentals - Total Amounts	(14)
Sublease rentals - 2018	(6)
Sublease rentals - 2019	(5)
Sublease rentals - 2020	(3)
Sublease rentals - 2021	0
Sublease rentals - 2022	0
Total committed operating leases less sublease rentals - Total Amounts	67
Total committed operating leases less sublease rentals - 2018	21
Total committed operating leases less sublease rentals - 2019	15
Total committed operating leases less sublease rentals - 2020	13
Total committed operating leases less sublease rentals - 2021	8
Total committed operating leases less sublease rentals - 2022	10
Rental expense	24	$ 24	$ 26
Sublease rental income	$ 5	$ 3	$ 3

Operating leases future minimum payments net.

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Operating leases future minimum payments net current.

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Operating leases future minimum payments net in five years.

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Operating leases future minimum payments net in four years.

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Operating leases future minimum payments net in three years.

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Operating leases future minimum payments net in two years.

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Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

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-Section 50
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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
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-Paragraph 2
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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
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Future rental payments receivable within one year of the balance sheet date under an operating lease.

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Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the fourth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the third year from the balance sheet date under an operating lease.

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Future rental payments receivable within the second year from the balance sheet date under an operating lease.

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The amount of revenue recognized for the period under subleasing arrangements.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 55
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=77891322&loc=d3e41620-112719

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This element represents the payments that the lessee is obligated to make or can be required to make in connection with a property under the terms of an agreement classified as an operating lease, excluding contingent rentals and a guarantee by the lessee of the lessor's debt and the lessee's obligation to pay (apart from the rental payments) executory costs such as insurance, maintenance, and taxes.

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