Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Employee waiting period after hire to participate in the defined contribution plans	90 years
Employee maximum contribution towards defined contribution plans as percentage of annual compensation	50.00%
Employee maximum contribution towards defined contribution plans as percentage of annual incentive plan bonus	80.00%
Employer's match in cash of non-union employee contributions on first specified percentage of eligible compensation	100.00%
First percentage of eligible compensation on which specified percentage of non-union employee contribution is matched by the employer in cash	3.00%
Employer's match in cash of non-union employee contributions on next specified percentage of eligible compensation	50.00%
Next percentage of eligible compensation on which specified percentage of non-union employee contribution is matched by the employer in cash	3.00%
Employer maximum match of non-union employee contribution on eligible compensation	4.50%
Defined contribution plans expense	$ 70	$ 64	$ 61
Accrued benefit liabilities	29	37
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Combined accumulated benefit obligation of pension plans	126	114
Plan assets of pension plans	120	103
Unfunded benefit obligation	6	11
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Unfunded benefit obligation	$ 23	$ 26

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

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Amount of benefit obligation for defined benefit plan with benefit obligation in excess of plan assets.

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Amount of cost for defined contribution plan.

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

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

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans.

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Employee maximum contribution towards defined contribution plans as percentage of annual incentive plan

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Employees Minimum Employment Period For Employer Contribution Eligibility

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Employer's match in cash of non-union employee contributions on first specified percentage of eligible compensation.

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