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Employee Benefit Plans (Details) (USD $)
In Thousands, unless otherwise specified |
3 Months Ended | |||||
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Mar. 31, 2014
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Mar. 31, 2013
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| Defined Benefit Plan Disclosure [Line Items] | ||||||
| Number of Union Pension Plans | 2 | |||||
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Pension Benefits
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| Components of net periodic benefit costs: | ||||||
| Service cost | $ 3,352 | $ 3,576 | ||||
| Interest cost | 1,659 | 1,350 | ||||
| Expected return on plan assets | (1,697) | (1,470) | ||||
| Amortization of prior service cost (credit)(1) | 33 | [1] | 77 | [1] | ||
| Amortization of actuarial loss(1) | 629 | [1] | 1,022 | [1] | ||
| Net periodic benefit cost (credit) | 3,976 | 4,555 | ||||
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Other Post-Retirement Benefits
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| Components of net periodic benefit costs: | ||||||
| Service cost | 67 | 77 | ||||
| Interest cost | 114 | 115 | ||||
| Expected return on plan assets | 0 | 0 | ||||
| Amortization of prior service cost (credit)(1) | (928) | [1] | (928) | [1] | ||
| Amortization of actuarial loss(1) | 195 | [1] | 308 | [1] | ||
| Net periodic benefit cost (credit) | $ (552) | $ (428) | ||||
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