Environmental Matters (Tables)

3 Months Ended

Mar. 31, 2017

Environmental Remediation Obligations [Abstract]

Schedule of Environmental Loss Contingencies by Site [Table Text Block]

	Current Liabilities						Non-Current Liabilities
	March 31,				December 31,		March 31,				December 31,
In thousands	2017		2016		2016		2017		2016		2016
Portland Harbor site:
Gasco/Siltronic Sediments	$	1,573	$	2,747	$	869	$	43,200	$	42,079	$	43,972
Other Portland Harbor	1,804		1,655		1,970		3,940		4,775		4,148
Gasco/Siltronic Upland site	10,335		10,626		10,657		50,189		51,403		49,183
Central Service Center site	68		25		73		—		—		—
Front Street site	858		1,071		906		7,777		7,746		7,786
Oregon Steel Mills	—		—		—		179		179		179
Total	$	14,638	$	16,124	$	14,475	$	105,285	$	106,182	$	105,268

Environmental Regulatory Table [Table Text Block]

	March 31,						December 31,
In thousands	2017			2016			2016
Deferred costs and interest (1)	$	49,373		$	57,359		$	53,039
Accrued site liabilities (2)	119,623			122,306			119,443
Insurance proceeds and interest	(99,195		)	(102,570		)	(98,523		)
Total regulatory asset deferral(1)	$	69,801		$	77,095		$	73,959
Current regulatory assets(3)	7,574			9,096			9,989
Long-term regulatory assets(3)	62,227			67,999			63,970