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DERIVATIVES AND RISK MANAGEMENT ACTIVITIES Table 3 - Impact of Derivatives on Earnings (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Derivative Instruments, Gain (Loss)    
Gain (loss) to be reclassified during next 12 months, forward-starting interest rate swaps $ (4,800)  
Designated as Hedging Instruments | Fair Value Hedges | Commodity contracts | Cost of product sales    
Derivative Instruments, Gain (Loss)    
Gain (loss) recognized in income on derivative (296) $ 2,097
Gain (loss) recognized in income on hedged item 237 (1,834)
Gain (loss) recognized in income for ineffective portion (59) 263
Designated as Hedging Instruments | Cash Flow Hedges | Interest rate swaps | Other comprehensive income    
Derivative Instruments, Gain (Loss)    
Gain (loss) recognized in other comprehensive income on derivative (effective portion) 17,421 39
Designated as Hedging Instruments | Cash Flow Hedges | Interest rate swaps | Interest expense, net    
Derivative Instruments, Gain (Loss)    
Gain (loss) reclassified from AOCI into interest expense, net (effective portion) (1,390) (1,799)
Not Designated as Hedging Instruments | Commodity contracts | Cost of product sales    
Derivative Instruments, Gain (Loss)    
Gain (loss) recognized in income on derivative $ (141) $ (138)