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Income Taxes - Schedule of Expiration Periods of Deferred Tax Assets (Detail) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | --- | --- | ---
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | $ 3,305 |  |  |
Tax credit carryforwards | 638 |  |  |
Other | 1,144 |  |  |
Valuation allowance | (2,584) | $ (1,940) | $ (1,291) | $ (1,151)
Deferred tax assets, net | 2,503 | $ 2,014 |  |
Expires within 10 years |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 81 |  |  |
Tax credit carryforwards | 531 |  |  |
Other | 0 |  |  |
Valuation allowance | (467) |  |  |
Deferred tax assets, net | 145 |  |  |
Expires within 11-20 years |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 781 |  |  |
Tax credit carryforwards | 97 |  |  |
Other | 0 |  |  |
Valuation allowance | (646) |  |  |
Deferred tax assets, net | 232 |  |  |
No expiration |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 2,443 |  |  |
Tax credit carryforwards | 10 |  |  |
Other | 84 |  |  |
Valuation allowance | (1,376) |  |  |
Deferred tax assets, net | 1,161 |  |  |
Other |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 0 |  |  |
Tax credit carryforwards | 0 |  |  |
Other | 1,060 |  |  |
Valuation allowance | (95) |  |  |
Deferred tax assets, net | $ 965 |  |  |

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- Definition Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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- Definition Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible tax credit carryforwards, classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -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://www.xbrl.org/2003/role/presentationRef -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 + Details
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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- Definition The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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