Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

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

	March 31,				December 31,
In thousands	2016		2015		2015
Natural gas (in therms):
Financial	317,100		229,925		346,875
Physical	169,978		250,250		404,645
Foreign exchange	$	6,852	$	8,690	$	9,025

Income Statement Presentation of Derivative Instruments [Text Block]

	Three Months Ended March 31,
	2016						2015
In thousands	Natural gas commodity			Foreign exchange			Natural gas commodity			Foreign exchange
(Expense) benefit to cost of gas	$	(16,379	)	$	241		$	(23,481	)	$	(741	)
Operating revenues	—			—			638			—
Less:
Amounts deferred to regulatory accounts on balance sheet	16,379			(241		)	23,065			741
Total gain in pre-tax earnings	$	—		$	—		$	222		$	—

Table Of Estimated Collateral Calls Table [Text Block]

			Credit Rating Downgrade Scenarios
In thousands	(Current Ratings) A+/A3		BBB+/Baa1		BBB/Baa2		BBB-/Baa3		Speculative
With Adequate Assurance Calls	$	—	$	—	$	—	$	2,341	$	15,600
Without Adequate Assurance Calls	—		—		—		2,341		13,381