The amount of employer securities or securities of parties related to the employer that are included in plan assets.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

+ References

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

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- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

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- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

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- Definition

Defined Benefit Plan Employee Vesting Period

+ References

No definition available.

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Employee Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Qualified employees maximum contribution to defined contribution savings plan allowed in percentage of annual compensation	75.00%
Company contribution to defined savings plan	4.00%
Company contribution, percentage company contribution matches of the employee's percentage contribution matched	100.00%
Employee retirement savings plan matching expenses	$ 156,000,000	$ 142,000,000	$ 131,000,000
Vesting service period for defined benefit pension plan	3 years
Plan assets of the qualified pension plans that have asset management arrangements with related parties	$ 798,000,000	48,000,000
Global Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	43.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	30.00%
Domestic Mid-Small Cap Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	7.00%
Emerging Markets Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Real Estate Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to qualified pension and postretirement welfare plan	$ 1,238,000,000	383,000,000
Pension Plans [Member] \| Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to qualified pension and postretirement welfare plan	1,200,000,000	358,000,000
Company contributions to pension and postretirement welfare plan in next fiscal year	0
Pension Plans [Member] \| Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to pension and postretirement welfare plan in next fiscal year	23,000,000
Postretirement Welfare Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to qualified pension and postretirement welfare plan	5,000,000	$ 7,000,000
Company contributions to pension and postretirement welfare plan in next fiscal year	$ 5,000,000