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Employee Retirement Plans (Narrative) (Details) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 USD ($) agreement employee | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligation | $ 1,070 | $ 1,377 | $ 1,685
Pre-tax accumulated other comprehensive loss - retirement benefit liability adjustment | (171) | (197) |
Net liability | $ 1,241 | $ 1,573 |
Number of employees | employee | 2,022 |  |
Employees represented by unions through CBAs, percentage | 11.00% |  |
Number of CBA's to be negotiated | agreement | 3 |  |
Number of CBA's | agreement | 6 |  |
Company's maximum contribution percentage | 5.00% |  |
National Integrated Group Pension Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
CBAs expiration date | Apr. 30, 2018 |  |

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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580 + Details
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- Definition Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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