Maximum annual compensation per employee subject to pension contribution.

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Percentage of pension benefits vested due after five years.

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Percentage of pension benefits vested due after four years.

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Percentage of pension benefits vested due after three years.

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Percentage of pension benefits vested due after two years.

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Shares issued under Omnibus Plan in connection with other than stock options, count.

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Shares issued under stock options plan counted in long-term incentive plan.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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

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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 cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cash outflow to satisfy grantee's tax withholding obligation for award under share-based payment arrangement.

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Amount of cost (reversal of cost) for pension benefits. Excludes other postretirement benefits.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

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Aggregate value of stock related to Restricted Stock Awards issued during the period.

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Benefit Plans (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
Benefit Plans (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pension and 401k expense	$ 4	$ 3	$ 6
Defined contribution pension [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contribution percentage of eligible employees compensation	10.00%
Vested after two years	20.00%
Vested after three years	60.00%
Vested after four years	80.00%
Vested after five years	100.00%
Qualified profit-sharing/401(k) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contribution percentage of eligible employees compensation	25.00%
Vested after two years	20.00%
Vested after three years	60.00%
Vested after four years	80.00%
Vested after five years	100.00%
Contributions percentage of employer match	5.00%
Maximum [Member] \| Defined contribution pension [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum annual compensation subject to pension	$ 2	2
Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shareholder approved increase in common stock reserved and available for issuance	14,000,000
Shares issued under Omnibus Plan in connection with stock options, count	1
Shares/units available for future grants	1,807,058
Omnibus Plan [Member] \| After May 1, 2012 Amendment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under Omnibus Plan in connection with other than stock options, count	1.28
Omnibus Plan [Member] \| Prior To May 1, 2012 Amendment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under Omnibus Plan in connection with other than stock options, count	2
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, value, restricted stock award, gross	$ 8	37
Share-based compensation expense (benefit)	12	6	$ 10
Tax charge related to share-based compensation	0	$ 0
Unrecognized compensation cost	$ 30
Expected to be recognized as expense over a weighted average period, years	2 years 10 months 24 days
Restricted Stock [Member] \| Stock Price Targets [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	221,213	247,286	65,287
Restricted Stock [Member] \| Internal Performance Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted			127,001
Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-term incentive awards vesting period, years	3 years
Restricted Stock [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-term incentive awards vesting period, years	7 years