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Income Tax Provision Differed from Amounts Computed at Statutory Federal Income Tax Rate and Significant Components (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Income Taxes [Line Items] |  |  |
Income tax provision at statutory rate | $ 1,050 | $ 1,337 | $ 1,477
State income taxes, net of federal income tax | 29 | 38 | 38
Foreign tax rate differential | (43) |  |
Foreign income taxes | 3 | 3 | 4
Nondeductible employee meals | 17 | 16 | 15
Impact of Tax Act | (192) |  |
Income tax adjustment from AOCI |  | 180 |
State rate change | 12 | (12) |
Valuation allowance | (16) | 20 | (4,662)
Other, net | 8 | (26) | 7
Income tax expense (benefit) | 868 | 1,556 | (3,121)
Current | (77) | (92) | 56
Deferred | 945 | 1,648 | (3,177)
Income tax expense (benefit) | 868 | 1,556 | (3,121)
United Airlines, Inc. |  |  |
Income Taxes [Line Items] |  |  |
Income tax provision at statutory rate | 1,051 | 1,338 | 1,477
State income taxes, net of federal income tax | 29 | 38 | 38
Foreign tax rate differential | (43) |  |
Foreign income taxes | 3 | 3 | 4
Nondeductible employee meals | 17 | 16 | 15
Impact of Tax Act | (209) |  |
Income tax adjustment from AOCI |  | 180 |
State rate change | 12 | (12) |
Valuation allowance | (16) | 20 | (4,621)
Other, net | 8 | (25) | 7
Income tax expense (benefit) | 852 | 1,558 | (3,080)
Current | (77) | (92) | 56
Deferred | 929 | 1,650 | (3,136)
Income tax expense (benefit) | $ 852 | $ 1,558 | $ (3,080)

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- Definition Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 + Details
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- Definition Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 + Details
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