PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Details 2) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Pension Benefits
     
Components of net pension cost      
Interest cost $ 3,571 $ 3,700 $ 3,816
Expected return on assets (6,100) (4,287) (4,195)
Recognized net actuarial loss 2,142 1,893 945
Net periodic pension (benefit) cost (387) 1,306 566
Amounts that will be amortized from accumulated other comprehensive income (loss) in next fiscal year      
Estimated net loss 1,400    
Estimated future benefit payments for all pension and postretirement plans      
2014 4,036    
2015 4,194    
2016 4,162    
2017 4,404    
2018 4,485    
2019-2023 24,737    
Pension Benefits | Consolidated plans
     
Significant assumptions used to calculate the net periodic pension cost and obligation      
Discount rate for periodic pension cost (as a percent) 3.95% 4.55% 5.55%
Discount rate for benefit obligation (as a percent) 4.80% 3.95% 4.55%
Expected long-term rate of return on plan assets (as a percent) 7.45% 8.00% 8.00%
Other Postretirement Benefits
     
Components of net pension cost      
Service cost 211 250 204
Interest cost 907 1,054 1,301
Amortization of transition obligation 164 164 164
Amortization of prior service cost (527) (452) 146
Recognized net actuarial loss 472 390 173
Net periodic pension (benefit) cost 1,227 1,406 1,988
Initial health care costs trend rate for participants under the age of 65 (as a percent)   6.00% 6.00%
Initial health care costs trend rate for participants over the age of 65 (as a percent) 7.50% 6.00% 7.00%
Projected ultimate health care costs trend rate in 2018 (as a percent) 5.00%    
Effect of one-percentage point change in assumed health-care cost trend rates      
Effect of one-percentage point increase on accumulated postretirement benefit obligation 604    
Effect of one-percentage point decrease on accumulated postretirement benefit obligation (705)    
Effect of one-percentage point increase on service and interest cost 25    
Effect of one-percentage point decrease on service and interest cost (25)    
Amounts that will be amortized from accumulated other comprehensive income (loss) in next fiscal year      
Estimated transition 164    
Estimated net loss 167    
Prior service cost (527)    
Estimated future benefit payments for all pension and postretirement plans      
2014 1,514    
2015 1,495    
2016 1,476    
2017 1,503    
2018 1,469    
2019-2023 $ 6,859    
Other Postretirement Benefits | Beneficial Bank Plans
     
Significant assumptions used to calculate the net periodic pension cost and obligation      
Discount rate for periodic pension cost (as a percent) 3.85% 4.50% 5.55%
Discount rate for benefit obligation (as a percent) 4.80% 3.85% 4.50%
Other Postretirement Benefits | FMS plans
     
Significant assumptions used to calculate the net periodic pension cost and obligation      
Discount rate for periodic pension cost (as a percent) 3.85% 4.50% 5.55%
Discount rate for benefit obligation (as a percent) 4.80% 3.85% 4.50%
Components of net pension cost      
Initial health care costs trend rate for participants over the age of 65 (as a percent) 7.50%   8.50%
Projected ultimate health care costs trend rate in 2018 (as a percent) 5.00%