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Weighted-Average Assumptions used to Determine Net Periodic Benefit Cost (Detail)
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12 Months Ended | ||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Pension Benefits [Member]
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| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.60% | 5.24% | 5.77% |
| Expected return on plan assets | 7.67% | 7.73% | 7.73% |
| Rate of compensation increase | 4.41% | 4.37% | 4.37% |
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Other Benefits [Member]
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| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.29% | 4.90% | 5.45% |
| Expected return on plan assets | 7.75% | 7.75% | 7.75% |
| Rate of compensation increase | |||
| X | ||||||||||
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- Definition
The interest rate used to adjust for the time value of money. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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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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| X | ||||||||||
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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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| X | ||||||||||
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- Details
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