Employee Retirement Plans - Pension expense (Details) $ in Thousands |
12 Months Ended | ||
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Dec. 31, 2017
USD ($)
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Dec. 31, 2016
USD ($)
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Dec. 31, 2015
USD ($)
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| Employee Retirement Plans | |||
| Number of regional multi-employer pension plans in which the entity participates | item | 34 | ||
| Pension Expense | $ 12,766 | $ 10,543 | $ 9,280 |
| Defined-contribution plans | |||
| Employee Retirement Plans | |||
| Pension Expense | 4,089 | 3,950 | 3,451 |
| Multi-employer plans | |||
| Employee Retirement Plans | |||
| Pension Expense | $ 8,677 | $ 6,593 | $ 5,829 |
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- Definition Represents the number of regional multi-employer pension plans in which the entity participates. No definition available.
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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 amount of pension benefit costs recognized during the period for (1) defined benefit plans and (2) defined contribution plans. For defined benefit plans, pension expense includes the following components: service cost, interest cost, expected return on plan assets, gain (loss) on plan assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. For defined contribution plans, the pension expense generally equals the firm's contribution to employees' accounts (if the firm contributes) during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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