Pension and Other Postretirement Benefits - Schedule of Benefit Payments Expected to be Paid and Expected Medicare Part D Subsidy Receipts (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2015	$ 890
2016	890
2017	900
2018	910
2019	920
2020 through 2024	4,670
Total benefit payments	9,180
Gross Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2015	230
2016	220
2017	220
2018	220
2019	220
2020 through 2024	1,000
Total benefit payments	2,110
Medicare Part D Subsidy Receipts [Member]
Defined Benefit Plan Disclosure [Line Items]
2015	15
2016	15
2017	15
2018	15
2019	15
2020 through 2024	85
Total benefit payments	160
Net Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2015	215
2016	205
2017	205
2018	205
2019	205
2020 through 2024	915
Total benefit payments	$ 1,950

Defined benefit plan expected future benefit payments.

No definition available.

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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- Definition

Amount of benefits from a defined benefit plan expected to be paid 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.

+ References

+ Details

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- Definition

Amount of benefits from a defined benefit plan expected to be paid 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.

+ References

+ Details

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- Definition

Amount of benefits from a defined benefit plan expected to be paid 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.

+ References

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- Definition

Amount of benefits from a defined benefit plan expected to be paid 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.

+ References

+ Details

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- Definition

Amount of benefits from a defined benefit plan expected to be paid 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.

+ References

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