Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

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

	March 31,				December 31,
In thousands	2017		2016		2016
Natural gas (in therms):
Financial	382,850		317,100		477,430
Physical	368,700		169,978		535,450
Foreign exchange	$	6,629	$	6,852	$	7,497

Income Statement Presentation of Derivative Instruments [Text Block]

	Three Months Ended March 31,
	2017						2016
In thousands	Natural gas commodity			Foreign exchange			Natural gas commodity			Foreign exchange
Benefit (expense) to cost of gas	$	(13,094	)	$	26		$	(7,215	)	$	404
Operating loss	(1,226		)	—			—			—
Amounts deferred to regulatory accounts on balance sheet	13,893			(26		)	7,215			(404		)
Total loss in pre-tax earnings	$	(427	)	$	—		$	—		$	—

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	$	—	$	—	$	—	$	(1,065	)	$	(522	)
Without Adequate Assurance Calls	—		—		—		(1,065		)	(160		)