Income Tax - Gross Deferred Tax Assets on Tax Loss Carryforwards and Investment Credits Expiration (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
2019	$ 15
2020	15
2021	3
2022	6
2023	7
Thereafter	557
Total	$ 603	$ 740

Deferred tax assets on tax loss carryforwards and investment credits expiration Thereafter.

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- Definition

Deferred Tax Assets On Tax Loss Carryforwards And Investment Credits Expiration Year Five

+ References

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- Definition

Deferred tax assets on tax loss carryforwards and investment credits expiration Year Four.

+ References

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- Definition

Deferred tax assets on tax loss carryforwards and investment credits expiration.

+ References

No definition available.

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- Definition

Deferred tax assets on tax loss carryforwards and investment credits expiration Year Three.

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- Definition

Deferred tax assets on tax loss carryforwards and investment credits expiration Year Two.

+ References

No definition available.

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- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115928272&loc=d3e28680-109314

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