Quarterly report pursuant to Section 13 or 15(d)

Benefit Plans (Details Textuals)

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Benefit Plans (Details Textuals) (USD $)
3 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets, Percentage 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 3.3Y  
Target allocation of plan assets in equity, percentage range minimum 50.00%  
Target allocation of plan assets in equity, percentage range maximum 70.00%  
Target allocation of plan assets in bonds, percentage range minimum 30.00%  
Target allocation of plan assets in bonds, percentage range maximum 50.00%  
Base pay contributed to the plan up to the first 3%  
Attributes of employees contribution to defined contribution plan Half of the employee contribution is 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 63.00%  
Covered Bonds [Member]
   
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets, Percentage 37.00%