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Pension and Postretirement Plans (Narrative) (Details)
2 Months Ended 3 Months Ended 10 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Investment
companies
Dec. 31, 2018
USD ($)
Investment
companies
Dec. 31, 2017
USD ($)
Investment
Sep. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Oct. 31, 2018
Dec. 31, 2018
USD ($)
multiemployer_plan
Investment
companies
Dec. 31, 2017
USD ($)
multiemployer_plan
Investment
Dec. 31, 2016
USD ($)
multiemployer_plan
Retirement Benefits Disclosure [Line Items]                  
Early retirement and special separation benefit program expense             $ 0 $ 1,825,000 $ 0
Expense associated with the retirement benefits provided under incentive savings plans             $ 8,600,000 $ 7,500,000 $ 7,500,000
Multiemployer Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Number of multiemployer plans contributed to | multiemployer_plan             1 1 1
Contributions to multiemployer pension plans             $ 100,000 $ 100,000 $ 100,000
Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Early retirement and special separation benefit program expense             0 1,825,000 0
Settlement   $ 26,900,000     $ 18,000,000   26,917,000 0 17,993,000
Accumulated benefit obligation $ 1,097,300,000 1,097,300,000 $ 1,261,800,000       1,097,300,000 1,261,800,000  
Company contributions             0 0  
Estimated employer contributions in next fiscal year $ 0 $ 0         0    
Net Periodic Cost (Benefit) for the Year             (74,031,000) (59,039,000) (49,104,000)
Curtailment             $ 806,000 $ 0 0
Percent of Plan Assets Managed Internally by Company             46.00%    
Percent Of Plan Assets Managed By Investment Companies             54.00%    
Number of investment companies actively managing plan assets | companies 2 2         2    
Percentage of total plan assets 100.00% 100.00% 100.00%       100.00% 100.00%  
Supplemental Executive Retirement Plan (SERP) [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Accumulated benefit obligation $ 102,200,000 $ 102,200,000 $ 108,000,000       $ 102,200,000 $ 108,000,000  
Company contributions             5,694,000 5,576,000  
Other Postretirement Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Company contributions             782,000 879,000  
Net Periodic Cost (Benefit) for the Year             (3,679,000) (2,232,000) 779,000
Curtailment             $ 3,380,000 $ 0 $ 0
Discount rate to determine benefit obligation 3.69% 3.69% 3.11%       3.69% 3.11%  
Discount rate to determine periodic cost 4.04%         3.11%   3.31% 3.45%
Other Postretirement Plans [Member] | Pre-Age 65 [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Assumed health care cost trend rate 7.41% 7.41%         7.41%    
Direction of change for assumed health care cost trend rate             decreasing    
Ultimate health care cost trend rate 4.50% 4.50%         4.50%    
Year that rate reaches ultimate trend rate             2026    
Other Postretirement Plans [Member] | Post-Age 65 [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Assumed health care cost trend rate 7.96% 7.96%         7.96%    
Direction of change for assumed health care cost trend rate             decreasing    
Ultimate health care cost trend rate 4.50% 4.50%         4.50%    
Year that rate reaches ultimate trend rate             2026    
Other Postretirement Plans [Member] | Medicare Advantage [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Assumed health care cost trend rate 12.74% 12.74%         12.74%    
Direction of change for assumed health care cost trend rate             decreasing    
Ultimate health care cost trend rate 4.50% 4.50%         4.50%    
Year that rate reaches ultimate trend rate             2028    
Berkshire Hathaway Common Stock [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Defined benefit plan, target allocation maximum percentage of assets, singular equity security, without prior approval by plan administrator             20.00%    
Single Equity Concentration [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Defined benefit plan, target allocation maximum percentage of assets, singular equity security, without prior approval by plan administrator             10.00%    
Value of investments $ 945,600,000 $ 945,600,000 $ 1,079,300,000       $ 945,600,000 $ 1,079,300,000  
Percentage of total plan assets 45.00% 45.00% 46.00%       45.00% 46.00%  
Single Equity Concentration [Member] | Equity securities [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Number of investments the company's pension plan held which individually exceed 10% of total plan assets | Investment 1 1 1       1 1  
Single Equity Concentration [Member] | Equity funds [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Number of investments the company's pension plan held which individually exceed 10% of total plan assets | Investment 1 1 1       1 1  
Defined Benefit Plan Assets Total [Member] | Concentration In Single Entity, Type Of Industry, Foreign Country Or Individual Fund [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Minimum percentage of plan assets considered as significant concentrations in pension plans             10.00%    
Separation Incentive Program [Member] | Pension Plans [Member] | Forney [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Early retirement and special separation benefit program expense       $ 900,000          
Education [Member] | Separation Incentive Program [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Early retirement and special separation benefit program expense     $ 900,000            
Maximum [Member] | Foreign Investments [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Defined benefit plan, target allocation percentage of assets 23.00% 23.00%         23.00%    
Minimum [Member] | Fixed income securities [Member] | Pension Plans [Member]                  
Retirement Benefits Disclosure [Line Items]                  
Defined benefit plan, target allocation percentage of assets 10.00% 10.00%         10.00%