Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2015

Summary of Derivative Instruments [Abstract]

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

	At December 31,
In thousands	2015		2014
Natural gas (in therms):
Financial	346,875		287,475
Physical	404,645		420,980
Foreign exchange	$	9,025	$	12,230

Income Statement Presentation of Derivative Instruments [Text Block]

	December 31, 2015						December 31, 2014
In thousands	Natural gas commodity			Foreign exchange			Natural gas commodity			Foreign exchange
Expense to cost of gas	$	(22,600	)	$	(419	)	$	(32,784	)	$	(382	)
Operating revenues	226			—			—			—
Less:
Amounts deferred to regulatory accounts on balance sheet	22,434			419			32,782			382
Total gain (loss) in pre-tax earnings	$	60		$	—		$	(2	)	$	—

Table Of Estimated Collateral Calls Table [Text Block]

			Credit Rating Downgrade Scenarios
In thousands	(Current Ratings) A+/A3		BBB+/Baa1		BBB/Baa2		BBB-/Baa3		Specul-ative
With Adequate Assurance Calls	$	—	$	—	$	—	$	4,852	$	21,185
Without Adequate Assurance Calls	—		—		—		4,164		15,497