v3.10.0.1
Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Jan. 01, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Summary of Significant Accounting Policies [Line Items]        
Operating expenses   $ 649,436 $ 577,978 $ 528,672
General and administrative   194,283 165,717 147,165
Other Nonoperating Income (Expense)   (13,868) (4,139) $ 6,466
Long-term pension and benefits   122,580 111,305  
Accumulated other comprehensive loss   (120,491) $ (137,578)  
Error in Actuarial Assumptions [Member]        
Summary of Significant Accounting Policies [Line Items]        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)   19,400    
Operating expenses   7,800    
General and administrative   4,700    
Other Nonoperating Income (Expense)   6,900    
Long-term pension and benefits   22,200    
Accumulated other comprehensive loss   $ 2,800    
Assets, Total [Member] | Accounting Standards Update 2016-02 [Member] | Scenario, Forecast [Member]        
Summary of Significant Accounting Policies [Line Items]        
New Accounting Pronouncement or Change in Accounting Principle, Effect on Financial Statement [Fixed List] $ 180,000      
Liabilities, Total [Member] | Accounting Standards Update 2016-02 [Member] | Scenario, Forecast [Member]        
Summary of Significant Accounting Policies [Line Items]        
New Accounting Pronouncement or Change in Accounting Principle, Effect on Financial Statement [Fixed List] $ 180,000