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Pension Plans and Other Postretirement Benefits - Schedule of Weighted-average Assumptions on Pension Plan Obligations, Other Postretirement Benefit ("OPEB") and Net Periodic Benefit Costs (Detail)
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12 Months Ended |
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Defined Benefit Pension Plans [Member] |
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| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
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| Discount rate |
2.01% |
3.30% |
3.05% |
| Pension Plan Obligations, Rate of increase in future compensation levels |
2.71% |
2.86% |
2.69% |
| Pension Plan Obligations, Expected long-term rate of return on plan assets |
0.00% |
0.00% |
0.00% |
| Net Periodic Benefit Costs, Discount rate |
3.30% |
3.05% |
4.49% |
| Net Periodic Benefit Costs, Rate of increase in future compensation levels |
2.86% |
2.69% |
2.64% |
| Net Periodic Benefit Costs, Expected long-term rate of return on plan assets |
2.83% |
2.44% |
4.09% |
| Other Postretirement Benefit Plans [Member] |
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| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
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| Discount rate |
6.40% |
4.72% |
3.93% |
| Other Postretirement Benefit Obligations, Initial health care cost trend rate |
8.05% |
6.67% |
7.00% |
| Other Postretirement Benefit Obligations, Ultimate health care cost trend rate |
5.43% |
5.00% |
5.00% |
| Other Postretirement Benefit Obligations, Year ultimate trend rate to be reached |
2021 |
2019 |
2019 |
| Net Periodic Benefit Costs, Discount rate |
6.69% |
3.93% |
5.08% |
| Net Periodic Benefit Costs, Initial health care cost trend rate |
6.67% |
7.00% |
7.33% |
| Net Periodic Benefit Costs, Ultimate health care cost trend rate |
5.00% |
5.00% |
5.00% |
| Net Periodic Benefit Costs, Year ultimate trend rate to be reached |
2019 |
2019 |
2019 |