Quarterly report pursuant to Section 13 or 15(d)

Benefit Plans (Details Textuals)

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Benefit Plans (Details Textuals) (USD $)
6 Months Ended
Jun. 30, 2011
Dec. 31, 2010
Jun. 30, 2010
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets, Percentage 100.00% 100.00% 100.00%
Benefit Plans (Textuals) [Abstract]      
Contribution to plan $ 50,000,000    
Employees retirement age for health care and life insurance benefits under unfunded defined benefit post-retirement plan 55 years    
Employees vesting service under defined benefit post-retirement plan, minimum 10 years    
Life insurance coverage, maximum $ 50,000    
Average duration of plan assets investment in bonds, years P3.5Y    
Target allocation of plan assets in equity, percentage 69.00%    
Target allocation of plan assets in bonds, percentage 31.00%    
Base pay contributed to the plan up to first 3%    
Attributes of employees contribution to defined contribution plan Half of the employee contribution was matched on the 4th and 5th percent of base pay contributed to the plan    
Equity Securities [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets, Percentage 67.00%    
Covered Bonds [Member]
     
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets, Percentage 33.00%