Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2014

Asset Retirement Obligation Disclosure [Abstract]

Schedule Of Changes In Asset Retirement Obligation

	2014			2013			2012
Asset retirement obligation at beginning of year	$	2,859		$	3,168		$	3,513
Liability settled	(41		)	(263		)	(559		)
Accretion expense (income)	210			(46		)	214
Asset retirement obligation at end of year	$	3,028		$	2,859		$	3,168

In addition to the AROs described above, on December 19, 2014, the EPA issued its pre-publication version of a final rule regarding the disposal of coal ash. This rule is expected to be published in the Federal Register in early 2015 and the rule is not effective until six months after it is published in the Federal Register; therefore, the Company does not have a revised legal obligation until the third quarter of 2015 when the rule is effective. The Company will continue to review the potential costs of complying with the new coal ash rule and its impacts on the valuation of the Company's ARO at Colstrip to restore ponds to their original states. The Company cannot currently estimate the cost impact of future regulation. If the Company incurs incremental costs as a result of these regulations, it would seek recovery in customer rates.