Actuarial Assumptions Used to Determine Net Periodic Benefit Cost (Detail) |
12 Months Ended | ||
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Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
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| Qualified defined benefit pension plans | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.125% | 4.375% | 4.00% |
| Expected long-term rate of return on assets | 7.50% | 8.00% | 8.00% |
| Rate of increase in future compensation levels | 4.50% | 4.50% | 4.30% |
| Retiree medical and life insurance plans | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.00% | 4.25% | 3.75% |
| Expected long-term rate of return on assets | 7.50% | 8.00% | 8.00% |
| Health care trend rate assumed for next year | 8.75% | 9.00% | 8.50% |
| Ultimate health care trend rate | 5.00% | 5.00% | 5.00% |
| Year that the ultimate health care trend rate is reached | 2032 | 2032 | 2029 |
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- Definition The interest rate used to adjust for the time value of money for the plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Expected rate of compensation increases (for pay-related plans). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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. No definition available.
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- Definition The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The ultimate trend rate for health care costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Year the ultimate health care cost trend rate is expected to be reached, in CCYY format. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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