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Benefit Plans - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]      
Minimum percentages of gain loss consider for amortization (in hundredths) 10.00%    
Minimum value of outstanding noncallable bonds used in hypothetical cash flow bond matching exercise $ 50,000,000    
Future earnings period used in determining the expected average rate of earnings 20 years    
Minimum percentage return should exceed growth in consumer price index annually (in hundredths) 5.75%    
Maximum investment in international mutual funds (in hundredths) 30.00%    
Percent of international mutual funds equity allocation in emerging markets (in hundredths) 3.00%    
Percent of international mutual funds equity allocation in companies primarily based in Europe and the Pacific Basin (in hundredths) 20.00%    
Discretionary profit sharing contribution as a percentage of participant's eligible compensation (in hundredths) 5.00%    
Matching contribution rate on employees' before-tax contributions, first contribution level (in hundredths) 80.00%    
Employee contributions subject to employer match, first contribution level $ 1,000    
Matching contribution rate on employees' before-tax contributions, second contribution level (in hundredths) 40.00%    
Employee contributions subject to employer match, second contribution level $ 2,000    
Matching contribution rate on employees' before-tax contributions, hired after 01/01/2014 (in hundredths) 100.00%    
Employee contributions subject to employer match for employees hired after 01/01/2014 (in hundredths) 4.00%    
Profit sharing and 401(k) savings plan expenses $ 5,900,000 $ 5,100,000 $ 5,000,000
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Lump sum pension plan benefit payments $ 11,200,000 $ 22,400,000  
Pension Plan | Equity securities      
Defined Benefit Plan Disclosure [Line Items]      
Target asset allocations, maximum (in hundredths) 40.00%    
Other Postretirement Benefit Plan      
Defined Benefit Plan Disclosure [Line Items]      
Health care trend rate used for pre-65 benefits (in hundredths) 7.00%    
Age of retirees at which retirement benefits under the plan are terminated 65 years    
Health care trend rate used for pre-65 benefits in 2016 (in hundredths) 6.50%    
Health care trend rate used for pre-65 benefits in 2020 (in hundredths) 5.00%    
Other Postretirement Benefit Plan | Equity securities      
Defined Benefit Plan Disclosure [Line Items]      
Target asset allocations, maximum (in hundredths) 100.00%