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Pension and Savings Plans (Details Textuals) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 USD ($) years plan | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Settlement Charge |  | $ 21,700,000 | $ 29,600,000 | $ 28,300,000
Defined Contribution Plans [Abstract] |  |  |  |
Number of 401(k) plans | plan |  | 2 |  |
Paid discretionary contributions to defined contribution pension plans, company match |  | $ 19,200,000 | 22,000,000 | 44,700,000
Additional discretionary contributions to defined contribution pension plans, performance feature |  |  | $ 19,500,000 | 18,300,000
Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement |  |  |  | $ 41,700,000
Actuarial gains and losses amortization corridor, percentage |  | 5.00% |  |
Period of amortization (in years) | years |  | 5 |  |
Estimated net actuarial loss that will be amortized from accumulated other comprehensive loss |  | $ 25,400,000 |  |
Estimated prior service cost that will be amortized from accumulated other comprehensive loss |  | $ 300,000 |  |
Expected rate of return on plan assets | 5.90% | 6.00% | 6.25% | 6.85%
Accumulated benefit obligation for pension plans |  | $ 959,300,000 | $ 939,300,000 |
Minimum funded percentage defined by the Pension Protection Act of 2006 |  | 80.00% |  |
Payment for Pension and Other Postretirement Benefits |  | $ 500,000 |  |
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year |  | 5,900,000 |  |
Settlement Charge |  | 0 | $ 0 | $ 8,700,000
Other Pension Plan, Postretirement or Supplemental Plans, Defined Benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Payment for Pension and Other Postretirement Benefits |  | $ 600,000 |  |
Equity Securities [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Target allocations for assets of Master Trust |  |  | 31.00% |
Fixed Income Investments [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Target allocations for assets of Master Trust |  |  | 69.00% |
Real Estate [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Target allocations for assets of Master Trust |  | 2.00% | 3.00% |

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- Definition Defined Benefit Plan Amortization Period. + References No definition available. + Details
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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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