Environmental Matters (Tables)

9 Months Ended

Sep. 30, 2016

Environmental Remediation Obligations [Abstract]

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

	Current Liabilities						Non-Current Liabilities
	September 30,				December 31,		September 30,				December 31,
In thousands	2016		2015		2015		2016		2015		2015
Portland Harbor site:
Gasco/Siltronic Sediments	$	1,726	$	1,236	$	2,229	$	42,880	$	38,533	$	42,641
Other Portland Harbor	1,461		1,243		1,972		4,362		4,563		5,073
Gasco Upland site	8,191		4,510		10,599		49,928		36,795		52,117
Siltronic Upland site	—		538		951		—		489		337
Central Service Center site	112		177		25		—		—		—
Front Street site	841		420		1,155		7,818		215		7,748
Oregon Steel Mills	—		—		—		179		179		179
Total	$	12,331	$	8,124	$	16,931	$	105,167	$	80,774	$	108,095

Environmental Regulatory Table [Table Text Block]

	September 30,						December 31,
In thousands	2016			2015			2015
Deferred costs and interest(1)	$	54,704		$	82,323		$	79,505
Accrued site liabilities(2)	117,202			88,898			125,026
Insurance proceeds and interest	(97,893		)	(121,414		)	(118,677		)
Total regulatory asset deferral(1)	74,013			49,807			85,854
Current regulatory assets(3)	9,734			12,364			9,270
Long-term regulatory assets(3)	64,279			37,443			76,584