Environmental Matters (details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Environmental Regulatory Table [Abstract]
Environmental Regulatory Assets Noncurrent	$ 126,482,000	$ 105,670,000
Cash Paid for Environmental Sites	71,124,000	55,553,000
Environmental Remediation Obligations [Abstract]
Loss Contingency Range Of Possible Loss Portland Harbor	$169 million to $1.8 billion
Gasco Siltronic Sediments Project Liability	34,000,000
Gasco Siltronic Sediments Other Liability	4,300,000
Portland Harbor Number Of Potentially Responsible Parties	more than 100
Loss Contingency Range Of Possible Loss Gasco Groundwater Source Control	$14 million and $30 million
Loss Contingency Range Of Possible Loss Gasco Siltronic	$38.3 million to $350 million
Damages Sought On Environmental Claims	50,000,000
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	24,466,000	20,183,000
Environmental Noncurrent Liabilities	45,235,000	52,506,000
Gasco Siltronic Sediments [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	2,207,000	1,614,000
Environmental Noncurrent Liabilities	36,087,000	35,797,000
Portland Harbor Other [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	1,767,000	1,893,000
Environmental Noncurrent Liabilities	3,160,000	7,066,000
Gasco Upland [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	18,722,000	14,092,000
Environmental Noncurrent Liabilities	5,028,000	8,900,000
Siltronic Upland [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	637,000	887,000
Environmental Noncurrent Liabilities	379,000	128,000
Central Service Center [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	140,000	0
Environmental Noncurrent Liabilities	396,000	495,000
Front Street [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	993,000	1,697,000
Environmental Noncurrent Liabilities	0	0
Other Environmental [Member]
Accrual for Environmental Loss Contingencies [Abstract]
Environmental Current Liabilities	0	0
Environmental Noncurrent Liabilities	$ 185,000	$ 120,000