The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References+ Details

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Litigation (Details) (USD $)						0 Months Ended
Litigation (Details) (USD $)	Mar. 31, 2014	Mar. 31, 2014 Colstrip Units 1 and 2 [Member]	Mar. 31, 2014 Colstrip Units 3 and 4 [Member]	Mar. 31, 2014 Pending Litigation [Member]	Dec. 31, 2013 Pending Litigation [Member]	Mar. 06, 2013 Pending Litigation [Member] Sierra Club and Montana Environmental Information Center [Member]	Mar. 06, 2013 Pending Litigation [Member] Failure to Update Title V Permit [Member] Sierra Club and Montana Environmental Information Center [Member] claim	Mar. 06, 2013 Pending Litigation [Member] Major Modifications to Title V Permit [Member] Sierra Club and Montana Environmental Information Center [Member] claim
Loss Contingencies [Line Items]
Residential Exchange Program Repayment	$ 62,900,000
Ownership interest (percent)		50.00%	25.00%
Numbe of claims							1	36
Damages sought, civil penalties to be used for beneficial mitigation projects						100,000
Litigation claims accrual				$ 1,360,000	$ 1,380,000