Derivative Instruments and Hedging Activities (Details Textual) - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Derivative [Line Items]
Losses in AOCI to be reclassified in 12 months	$ (1,400,000)
Margin Deposit Assets	500,000		$ 600,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount outstanding			6,500,000
Losses recognized on de-designated derivative contracts	(1,000,000)	$ 200,000
Gains included in other comprehensive income for de-designated derivative contracts	0	$ 100,000
Commodity Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liability	1,000,000		500,000
Derivative Asset	0		0
Commodity Contract [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount outstanding	29,100,000		23,600,000
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount outstanding	$ 6,800,000		$ 8,300,000