Derivative Instruments (tables)

3 Months Ended

Mar. 31, 2013

Summary of Derivative Instruments [Abstract]

Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]

	March 31,				December 31,
Dollars in thousands	2013		2012		2012
Open position absolute notional amount:
Natural gas (millions of therms)	30.2		32.8		39.5
Foreign exchange	$	16,322	$	12,954	$	13,231

Income Statement Presentation of Derivative Instruments [Text Block]

	Three Months Ended
	March 31, 2013						March 31, 2012
In thousands	Natural gas commodity			Foreign currency			Natural gas commodity			Foreign currency
Cost of sales	$	7,183		$	—		$	(55,894	)	$	—
Other comprehensive income (loss)	—			(239		)	—			126
Less:
Amounts deferred to regulatory accounts	(7,037		)	239			55,894			(126		)
Total gain in pre-tax earnings	$	146		$	—		$	—		$	—

Credit Rating Downgrade Scenarios [Text Block]

			Credit Rating Downgrade Scenarios
In thousands	(Current Ratings) A+/A3		BBB+/Baa1		BBB/Baa2		BBB-/Baa3		Speculative
With Adequate Assurance Calls	$	—	$	—	$	—	$	—	$	8,290
Without Adequate Assurance Calls	—		—		—		—		5,516