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Pension and Postretirement Plans (Narrative) (Details)
3 Months Ended 12 Months Ended
Dec. 31, 2017
USD ($)
Investment
companies
Sep. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Sep. 30, 2015
USD ($)
Dec. 31, 2017
USD ($)
multiemployer_plan
Investment
companies
Dec. 31, 2016
USD ($)
multiemployer_plan
Dec. 31, 2015
USD ($)
multiemployer_plan
Retirement Benefits Disclosure [Line Items]                
Early retirement and special separation benefit program expense           $ 1,825,000 $ 0 $ 4,606,000
Expense associated with the retirement benefits provided under incentive savings plans           $ 7,500,000 $ 7,500,000 $ 7,600,000
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           1,825,000 0 4,606,000
Settlement     $ 18,000,000     0 17,993,000 0
Accumulated benefit obligation $ 1,261,800,000   $ 1,137,900,000     1,261,800,000 1,137,900,000  
Company contributions           0 0  
Estimated employer contributions in next fiscal year $ 0         0    
Net Periodic Cost (Benefit) for the Year           (59,039,000) (49,104,000) (63,269,000)
Curtailment           $ 0 $ 0 3,267,000
Percent of Plan Assets Managed Internally by Company           45.00%    
Percent Of Plan Assets Managed By Investment Companies           55.00%    
Number of investment companies actively managing plan assets | companies 2         2    
Percentage of total plan assets 100.00%   100.00%     100.00% 100.00%  
Pension Plans [Member] | Discontinued Operations [Member]                
Retirement Benefits Disclosure [Line Items]                
Net Periodic Cost (Benefit) for the Year               1,900,000
Supplemental Executive Retirement Plan (SERP) [Member]                
Retirement Benefits Disclosure [Line Items]                
Accumulated benefit obligation $ 108,000,000   $ 103,000,000     $ 108,000,000 $ 103,000,000  
Company contributions           5,576,000 4,967,000  
Supplemental Executive Retirement Plan (SERP) [Member] | Discontinued Operations [Member]                
Retirement Benefits Disclosure [Line Items]                
Net Periodic Cost (Benefit) for the Year               $ 200,000
Other Postretirement Plans [Member]                
Retirement Benefits Disclosure [Line Items]                
Company contributions           $ 879,000 $ 852,000  
Discount rate to determine benefit obligation 3.11%   3.31%     3.11% 3.31%  
Discount rate to determine periodic cost           3.31% 3.45% 3.25%
Other Postretirement Plans [Member] | Pre-Age 65 [Member]                
Retirement Benefits Disclosure [Line Items]                
Assumed health care cost trend rate 7.81%         7.81%    
Direction of change for assumed health care cost trend rate           decreasing    
Ultimate health care cost trend rate 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 8.42%         8.42%    
Direction of change for assumed health care cost trend rate           decreasing    
Ultimate health care cost trend rate 4.50%         4.50%    
Year that rate reaches ultimate trend rate           2026    
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 $ 1,079,300,000   $ 978,800,000     $ 1,079,300,000 $ 978,800,000  
Percentage of total plan assets 46.00%   48.00%     46.00% 48.00%  
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    
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    
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%    
Special Incentive Program [Member] | Pension Plans [Member] | Corporate office [Member]                
Retirement Benefits Disclosure [Line Items]                
Early retirement and special separation benefit program expense       $ 900,000        
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] | Special Incentive Program [Member] | Pension Plans [Member]                
Retirement Benefits Disclosure [Line Items]                
Early retirement and special separation benefit program expense         $ 3,700,000      
Education [Member] | Separation Incentive Program [Member] | Pension Plans [Member]                
Retirement Benefits Disclosure [Line Items]                
Early retirement and special separation benefit program expense $ 900,000              
Cable Spin-Off [Member] | Pension Plans [Member] | Discontinued Operations [Member]                
Retirement Benefits Disclosure [Line Items]                
Curtailment               $ 2,200,000
Sale Of KHE Campuses Business [Member] | Pension Plans [Member]                
Retirement Benefits Disclosure [Line Items]                
Curtailment               $ 1,100,000
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%    
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%