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Benefit Plans (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Pension and 401k expense | $ 4 | $ 4 | $ 3
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 |  |
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 | 16,500,000 |  |
Shares issued under Omnibus Plan in connection with stock options, count | 1 |  |
Shares/units available for future grants | 3,338,822 |  |
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 | $ 7 | 8 |
Share-based compensation expense (benefit) | 11 | 12 | 6
Tax charge related to share-based compensation | 0 | $ 0 | $ 0
Unrecognized compensation cost | $ 26 |  |
Expected to be recognized as expense over a weighted average period, years | 2 years 5 months 12 days |  |
Restricted Stock [Member] | Stock Price Targets [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Restricted shares granted | 502,738 | 221,213 | 247,286
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 |  |

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