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Retirement Benefit Plans (Details) (USD $)
12 Months Ended
Dec. 29, 2012
Dec. 31, 2011
Jan. 01, 2011
Defined Benefit Plan Disclosure [Line Items]      
Contributions made by Company   $ 5,000,000  
Change in fair value of plan assets [Roll Forward]      
Employer contributions   5,000,000  
Funded status [Abstract]      
Net amount recognized in the balance sheet (20,181,361) (15,811,622)  
Assumptions used to determine the projected benefit obligations [Abstract]      
Discount rate (in hundredths) 3.90% 4.55%  
Expected return on plan assets (in hundredths) 8.00% 8.00%  
Rate of compensation increase (in hundredths) 3.25% 3.25%  
Accumulated benefit obligation for all qualified and nonqualified defined benefit pension plans 65,809,208 56,588,593  
Pension plans with projected benefit obligation and accumulated benefit obligation in excess of plan assets [Abstract]      
Number of plans 6 6  
Projected benefit obligation 74,825,969 64,709,379  
Accumulated benefit obligation 66,735,124 56,588,593  
Fair value of plan assets 54,644,608 48,897,760  
Net amount recognized in accrued benefit liability (20,181,361) (15,811,622)  
Estimated future benefit payments to participants [Abstract]      
Period of horizon for various asset classes used in calculating expected long-term rates of return 10 years    
Number of shares of employer common stock included plan assets (in shares) 193,624 193,624  
Value of employer common stock included plan assets 3,063,132 3,891,842  
Dividends received from employer common stock 96,812 69,705  
Health care cost trend rate for participants after January 1, 1991 (in hundredths)       
Ultimate health care cost trend rate (in hundredths) 4.50%    
Effect of one-percentage-point change in assumed health care cost trend rates on postretirement benefit plan [Abstract]      
Percentage of voluntary contributions allowed to participants, maximum (in hundredths) 100.00%    
Employer contributions made 187,531 179,400 171,326
The Eastern Company Common Stock [Member]
     
Estimated future benefit payments to participants [Abstract]      
Long-term target allocations for plan assets (in hundredths) 50.00%    
Long Duration Fixed Income [Member]
     
Estimated future benefit payments to participants [Abstract]      
Long-term target plan asset allocations relating to fixed income (in hundredths) 20.00%    
Fixed income [Member]
     
Estimated future benefit payments to participants [Abstract]      
Long-term target allocations for plan assets (in hundredths) 50.00%    
Pension Benefits [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Contributions made by Company 3,778,692 7,456,298  
Components of the net periodic benefit cost [Abstract]      
Service cost 2,642,373 2,141,306 2,223,762
Interest cost 2,868,528 2,949,672 2,908,962
Expected return on plan assets (3,930,988) (3,650,282) (3,345,102)
Amortization of prior service cost 221,049 194,148 204,569
Amortization of the net loss 1,111,900 897,052 843,154
Net periodic benefit cost 2,912,862 2,531,896 2,835,345
Assumptions used to determine net periodic benefit cost [Abstract]      
Discount rate (in hundredths) 3.90% 5.35% 5.85%
Expected return on plan assets (in hundredths) 8.00% 8.50% 8.50%
Rate of compensation increase (in hundredths) 3.25% 4.25% 4.25%
Change in benefit obligation [Roll Forward]      
Benefit obligation at beginning of year 64,709,379 56,979,912  
Change due to availability of final actual assets and census data 0 0  
Plan amendment 831,201 0  
Service cost 2,642,373 2,141,306 2,223,762
Interest cost 2,868,528 2,949,672 2,908,962
Actuarial loss 6,117,680 4,864,293  
Benefits paid (2,343,192) (2,225,804)  
Benefit obligation at end of year 74,825,969 64,709,379 56,979,912
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at beginning of year 48,897,760 42,966,643  
Change due to availability of final actual assets and census data 0 0  
Actual return on plan assets 4,311,348 700,623  
Employer contributions 3,778,692 7,456,298  
Benefits paid (2,343,192) (2,225,804)  
Fair value of plan assets at end of year 54,644,608 48,897,760 42,966,643
Funded status [Abstract]      
Net amount recognized in the balance sheet (20,181,361) (15,811,622)  
Amounts recognized in accumulated other comprehensive income [Abstract]      
Net loss (28,346,776) (23,721,356)  
Prior service (cost) credit (937,936) (327,784)  
Total (29,284,712) (24,049,140) (17,326,388)
Defined Benefit Plan, Change in components of accumulated other comprehensive income [Abstract]      
Balance at beginning of period (24,049,140) (17,326,388)  
Change due to availability of final actual assets and census data 0 0  
Charged to net periodic benefit cost [Abstract]      
Prior service cost 221,049 194,148 204,569
Net loss (gain) 1,111,900 897,052 843,154
Other changes [Abstract]      
Liability gains (6,568,521) (7,813,952)  
Balance at end of period (29,284,712) (24,049,140) (17,326,388)
Amounts that will be amortized from accumulated other comprehensive income in next fiscal year [Abstract]      
Net (loss) gain 1,423,431    
Prior service cost (credit) 245,427    
Pension plans with projected benefit obligation and accumulated benefit obligation in excess of plan assets [Abstract]      
Net amount recognized in accrued benefit liability (20,181,361) (15,811,622)  
Estimated future benefit payments to participants [Abstract]      
2013 2,800,000    
2014 2,800,000    
2015 2,900,000    
2016 3,100,000    
2017 3,200,000    
2018 through 2022 19,000,000    
Contributions expected to be made by Company in next fiscal year 1,900,000    
Fair value of plan assets 54,644,608 48,897,760 42,966,643
Pension Benefits [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,063,132 3,891,842  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,063,132 3,891,842  
Pension Benefits [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 51,581,476 45,005,918  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 51,581,476 45,005,918  
Pension Benefits [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Pension Benefits [Member] | Common/Collective Trust Funds [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 193,497 5,202,216  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 193,497 5,202,216  
Pension Benefits [Member] | Common/Collective Trust Funds [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Pension Benefits [Member] | Common/Collective Trust Funds [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 193,497 5,202,216  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 193,497 5,202,216  
Pension Benefits [Member] | Common/Collective Trust Funds [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Pension Benefits [Member] | The Eastern Company Common Stock [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,063,132 3,891,842  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,063,132 3,891,842  
Pension Benefits [Member] | The Eastern Company Common Stock [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,063,132 3,891,842  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,063,132 3,891,842  
Pension Benefits [Member] | The Eastern Company Common Stock [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Pension Benefits [Member] | The Eastern Company Common Stock [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Pension Benefits [Member] | U.S. Large Cap [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 5,826,726 [1] 5,339,876  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 5,826,726 [1] 5,339,876  
Pension Benefits [Member] | U.S. Large Cap [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [1] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [1] 0  
Pension Benefits [Member] | U.S. Large Cap [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 5,826,726 [1] 5,339,876  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 5,826,726 [1] 5,339,876  
Pension Benefits [Member] | U.S. Large Cap [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [1] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [1] 0  
Pension Benefits [Member] | U.S. Small Cap [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,964,072 [2] 3,090,711  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,964,072 [2] 3,090,711  
Pension Benefits [Member] | U.S. Small Cap [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [2] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [2] 0  
Pension Benefits [Member] | U.S. Small Cap [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,964,072 [2] 3,090,711  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,964,072 [2] 3,090,711  
Pension Benefits [Member] | U.S. Small Cap [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [2] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [2] 0  
Pension Benefits [Member] | Concentrated Equity [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 4,899,023 [3] 3,803,417  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 4,899,023 [3] 3,803,417  
Pension Benefits [Member] | Concentrated Equity [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [3] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [3] 0  
Pension Benefits [Member] | Concentrated Equity [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 4,899,023 [3] 3,803,417  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 4,899,023 [3] 3,803,417  
Pension Benefits [Member] | Concentrated Equity [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [3] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [3] 0  
Pension Benefits [Member] | International Large Cap with Active Currency [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 6,999,997 [4] 6,292,803  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 6,999,997 [4] 6,292,803  
Pension Benefits [Member] | International Large Cap with Active Currency [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [4] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [4] 0  
Pension Benefits [Member] | International Large Cap with Active Currency [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 6,999,997 [4] 6,292,803  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 6,999,997 [4] 6,292,803  
Pension Benefits [Member] | International Large Cap with Active Currency [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [4] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [4] 0  
Pension Benefits [Member] | Emerging Market [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,017,350 [5] 2,175,968  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,017,350 [5] 2,175,968  
Pension Benefits [Member] | Emerging Market [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [5] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [5] 0  
Pension Benefits [Member] | Emerging Market [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 3,017,350 [5] 2,175,968  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 3,017,350 [5] 2,175,968  
Pension Benefits [Member] | Emerging Market [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [5] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [5] 0  
Pension Benefits [Member] | Intermediate Bond [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 14,368,745 [6] 13,103,043  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 14,368,745 [6] 13,103,043  
Pension Benefits [Member] | Intermediate Bond [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [6] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [6] 0  
Pension Benefits [Member] | Intermediate Bond [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 14,368,745 [6] 13,103,043  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 14,368,745 [6] 13,103,043  
Pension Benefits [Member] | Intermediate Bond [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [6] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [6] 0  
Pension Benefits [Member] | 6 Year Target Duration LDI Fixed Income Fund [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 215,604 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 215,604 [7]    
Pension Benefits [Member] | 6 Year Target Duration LDI Fixed Income Fund [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 6 Year Target Duration LDI Fixed Income Fund [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 215,604 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 215,604 [7]    
Pension Benefits [Member] | 6 Year Target Duration LDI Fixed Income Fund [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 8 Year Target Duration LDI Fixed Income Fund [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 214,968 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 214,968 [7]    
Pension Benefits [Member] | 8 Year Target Duration LDI Fixed Income Fund [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 8 Year Target Duration LDI Fixed Income Fund [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 214,968 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 214,968 [7]    
Pension Benefits [Member] | 8 Year Target Duration LDI Fixed Income Fund [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 10 Year Target Duration LDI Fixed Income Fund [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 306,535 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 306,535 [7]    
Pension Benefits [Member] | 10 Year Target Duration LDI Fixed Income Fund [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 10 Year Target Duration LDI Fixed Income Fund [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 306,535 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 306,535 [7]    
Pension Benefits [Member] | 10 Year Target Duration LDI Fixed Income Fund [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 12 Year Target Duration LDI Fixed Income Fund [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 824,342 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 824,342 [7]    
Pension Benefits [Member] | 12 Year Target Duration LDI Fixed Income Fund [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 12 Year Target Duration LDI Fixed Income Fund [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 824,342 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 824,342 [7]    
Pension Benefits [Member] | 12 Year Target Duration LDI Fixed Income Fund [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 14 Year Target Duration LDI Fixed Income Fund [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 1,087,074 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 1,087,074 [7]    
Pension Benefits [Member] | 14 Year Target Duration LDI Fixed Income Fund [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 14 Year Target Duration LDI Fixed Income Fund [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 1,087,074 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 1,087,074 [7]    
Pension Benefits [Member] | 14 Year Target Duration LDI Fixed Income Fund [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 16 Year Target Duration LDI Fixed Income Fund [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 426,544 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 426,544 [7]    
Pension Benefits [Member] | 16 Year Target Duration LDI Fixed Income Fund [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | 16 Year Target Duration LDI Fixed Income Fund [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 426,544 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 426,544 [7]    
Pension Benefits [Member] | 16 Year Target Duration LDI Fixed Income Fund [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [7]    
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [7]    
Pension Benefits [Member] | Long Duration Fixed Income [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year   2,658,161 [8]  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets   2,658,161 [8]  
Pension Benefits [Member] | Long Duration Fixed Income [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year   0 [8]  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets   0 [8]  
Pension Benefits [Member] | Long Duration Fixed Income [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year   2,658,161 [8]  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets   2,658,161 [8]  
Pension Benefits [Member] | Long Duration Fixed Income [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year   0 [8]  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets   0 [8]  
Pension Benefits [Member] | Long Duration Fixed Credit [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 6,684,999 [9] 1,120,643  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 6,684,999 [9] 1,120,643  
Pension Benefits [Member] | Long Duration Fixed Credit [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [9] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [9] 0  
Pension Benefits [Member] | Long Duration Fixed Credit [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 6,684,999 [9] 1,120,643  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 6,684,999 [9] 1,120,643  
Pension Benefits [Member] | Long Duration Fixed Credit [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 [9] 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 [9] 0  
Pension Benefits [Member] | Insurance Contracts [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 2,552,000 2,219,080  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 2,552,000 2,219,080  
Pension Benefits [Member] | Insurance Contracts [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Pension Benefits [Member] | Insurance Contracts [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 2,552,000 2,219,080  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 2,552,000 2,219,080  
Pension Benefits [Member] | Insurance Contracts [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Postretirement Benefits [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Contributions made by Company 71,655 139,705  
Components of the net periodic benefit cost [Abstract]      
Service cost 173,613 126,464 110,786
Interest cost 143,388 136,752 134,977
Expected return on plan assets (46,255) (52,920) (59,327)
Amortization of prior service cost (23,889) (23,888) (23,888)
Amortization of the net loss (50,784) (46,380) (52,650)
Net periodic benefit cost 196,073 140,028 109,898
Assumptions used to determine net periodic benefit cost [Abstract]      
Discount rate (in hundredths) 3.90% 5.35% 5.85%
Expected return on plan assets (in hundredths) 8.00% 8.50% 8.50%
Change in benefit obligation [Roll Forward]      
Benefit obligation at beginning of year 3,069,155 2,629,606  
Change due to availability of final actual assets and census data 151,397 0  
Plan amendment 0 0  
Service cost 173,613 126,464 110,786
Interest cost 143,388 136,752 134,977
Actuarial loss 301,076 316,038  
Benefits paid (126,124) (139,705)  
Benefit obligation at end of year 3,712,505 3,069,155 2,629,606
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at beginning of year 1,215,998 1,168,235  
Change due to availability of final actual assets and census data (3,005) (5,157)  
Actual return on plan assets 46,255 52,920  
Employer contributions 71,655 139,705  
Benefits paid (126,124) (139,705)  
Fair value of plan assets at end of year 1,204,779 1,215,998 1,168,235
Funded status [Abstract]      
Net amount recognized in the balance sheet (2,507,726) (1,853,157)  
Amounts recognized in accumulated other comprehensive income [Abstract]      
Net loss (621,467) (115,205)  
Prior service (cost) credit 135,396 159,285  
Total (486,071) 44,080 435,543
Defined Benefit Plan, Change in components of accumulated other comprehensive income [Abstract]      
Balance at beginning of period 44,080 435,543  
Change due to availability of final actual assets and census data (154,402) (5,157)  
Charged to net periodic benefit cost [Abstract]      
Prior service cost (23,889) (23,888) (23,888)
Net loss (gain) (50,784) (46,380) (52,650)
Other changes [Abstract]      
Liability gains (301,076) (316,038)  
Balance at end of period (486,071) 44,080 435,543
Amounts that will be amortized from accumulated other comprehensive income in next fiscal year [Abstract]      
Net (loss) gain 19,858    
Prior service cost (credit) 23,888    
Pension plans with projected benefit obligation and accumulated benefit obligation in excess of plan assets [Abstract]      
Net amount recognized in accrued benefit liability (2,507,726) (1,853,157)  
Estimated future benefit payments to participants [Abstract]      
2013 155,000    
2014 170,000    
2015 177,000    
2016 189,000    
2017 197,000    
2018 through 2022 1,140,000    
Contributions expected to be made by Company in next fiscal year 155,000    
Fair value of plan assets 1,204,779 1,215,998 1,168,235
Life insurance cost trend rate (in hundredths) 1.00%    
Effect of one-percentage-point change in assumed health care cost trend rates on postretirement benefit plan [Abstract]      
Effect of 1-percentage point increase on total of service and interest cost components 56,711    
Effect of 1-percentage point decrease on total of service and interest cost components (45,651)    
Effect of 1-percentage point increase on postretirement benefit obligation 598,791    
Effect of 1-percentage point decrease on postretirement benefit obligation (487,508)    
Postretirement Benefits [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Postretirement Benefits [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Postretirement Benefits [Member] | Level 3 [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Contributions made by Company 71,655 139,705  
Change in benefit obligation [Roll Forward]      
Benefits paid (126,124) (139,705)  
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at beginning of year 1,215,998 1,168,235  
Change due to availability of final actual assets and census data (3,005) (5,157)  
Actual return on plan assets 46,255 52,920  
Employer contributions 71,655 139,705  
Benefits paid (126,124) (139,705)  
Fair value of plan assets at end of year 1,204,779 1,215,998  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 1,204,779 1,215,998  
Postretirement Benefits [Member] | Insurance Contracts [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 1,204,779 1,215,998  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 1,204,779 1,215,998  
Postretirement Benefits [Member] | Insurance Contracts [Member] | Level 1 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Postretirement Benefits [Member] | Insurance Contracts [Member] | Level 2 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 0 0  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets 0 0  
Postretirement Benefits [Member] | Insurance Contracts [Member] | Level 3 [Member]
     
Change in fair value of plan assets [Roll Forward]      
Fair value of plan assets at end of year 1,204,779 1,215,998  
Estimated future benefit payments to participants [Abstract]      
Fair value of plan assets $ 1,204,779 $ 1,215,998  
[1] The investment objective of the large cap fund is to outperform the Russell 1000® Index. The fund is designed to provide for long-term growth of capital by utilizing a diversified group of quantitative investment strategies that seek to identify securities that have exposure to factors that the underlying advisors' research has found to be predictive of future excess returns. The advisors' portfolios are quantitatively structured to gain exposure to these predictive characteristics while minimizing unintended risk exposures.
[2] The small cap fund has an objective to outperform the Russell 2500® Index The fund is designed to achieve consistency by combining advisors whose complementary disciplined processes employ distinct methods for identifying small capitalization U.S. stocks with strong return potential. Advisors in the fund use a wide range of criteria and disciplines in their stock selection, focusing on factors such as: undervalued or under-researched companies, special situations, emerging growth, asset plays or turnarounds.
[3] The investment objective of the concentrated equity fund is to outperform the Russell 1000® Index. The fund is designed to achieve this by combining strategies with different payoffs over different phases of an economic and stock market cycle. To help achieve this objective, multiple advisors and strategies are employed to reduce "scenario risk." These multiple strategies are in the form of multiple investment styles (e.g., growth, market oriented, and value), multiple sub-styles, and different ways of identifying undervalued securities.
[4] The international fund with active currency has an investment objective of outperforming the Russell Development ex-U.S. Large Cap Index Net. The fund is designed to provide the potential for long-term growth of capital by utilizing a diversified group of investment advisors that the Trustee's manager research indicates will outperform over a full market cycle. The investment advisors' portfolios are combined to form a fund that emphasizes their strengths while minimizing unintended risk exposures
[5] The emerging market fund seeks to outperform the Russell Emerging Markets Index Net. The fund is designed to provide the potential for long-term growth of capital by utilizing a diversified market group of investment advisors that the Trustee's manager research indicates will outperform over a full market cycle. The investment advisors' portfolios are combined to form a fund that emphasizes their strengths while minimizing unintended risk exposures.
[6] Fixed income common fund investments have an investment objective of outperforming the Barclays Capital U.S. Aggregate Bond Index over a full market cycle. The fund is designed to provide current income, and as a secondary objective, capital appreciation through a variety of diversified strategies including sector rotation, modest interest rate timing, security selection and tactical use of high yield and emerging market bonds. The portfolio diversification provides protection against a single security or class of securities having a disproportionate impact on aggregate performance. To help achieve the objective, the fund is actively managed by multiple advisors who use a variety of investment strategies to create a broad market exposure. The fund's advisors have distinct but complementary investment styles. These advisors generally have similar universes of investable securities but have different areas of specialization and expertise within intermediate duration securities.
[7] The Target Duration LDI Fixed Income Funds seek to outperform their respective Barclays-Russell LDI Indexes over a full market cycle. These Funds seek to provide current income, and as a secondary objective, capital appreciation through diversified strategies including sector rotation, modest interest rate timing, security selection and tactical use of high yield and emerging market bonds. The Funds will generally be used in combination with other bond funds to enable the plans to gain additional credit exposure within their asset portfolio, with the goal of reducing the mismatch between a plan's assets and liabilities.
[8] The long duration fixed income fund seeks to outperform the Barclays Capital U.S. Long Government/Credit Index over a full market cycle. This fund is designed to provide current income, and as a secondary objective, capital appreciation through diversified strategies including sector rotation, modest interest rate timing, security selection and tactical use of high yield and emerging market bonds. The fund will generally be used in combination with other bond funds, with the goal of reducing the mismatch between a plan's assets and liabilities. In 2012, this fund was replaced by the Target Duration LDI Fixed Income Funds. See (g) above.
[9] The long duration fixed credit fund seeks to outperform the Barclays Capital Long Credit Index over a full market cycle. The fund seeks to provide current income, and as a secondary objective, capital appreciation through diversified strategies including sector rotation, modest interest rate timing, security selection and tactical use of high yield and emerging market bonds. The fund will generally be used in combination with other bond funds, with the goal of reducing the mismatch between a plan's assets and liabilities.