Asset Retirement Obligations

9 Months Ended

Sep. 30, 2016

Asset Retirement Obligation [Abstract]

Questar Gas records an ARO along with an increase to the carrying value of the related property, plant and equipment when there is a legal obligation associated with the retirement of a tangible long-lived asset. The fair value of retirement costs is estimated by the Company based on abandonment costs of similar properties and depreciated over the life of the related assets. Revisions to estimates result from material changes in the expected timing or amount of cash flows associated with AROs. As a result of a change in the estimated timing of cash flows for the interim retirement of natural gas pipeline components, Questar Gas recorded an increase of $75.1 million to AROs in the third quarter of 2016. Income or expense resulting from the settlement of ARO liabilities sold is included in other operations and maintenance on the Condensed Statements of Income. The current portion of the ARO balance is $1.5 million and is included in other current liabilities on the Condensed Balance Sheets. The ARO liability is adjusted to present value each period through an accretion calculation using a credit-adjusted risk-free interest rate. Changes in Questar Gas' AROs from the Condensed Balance Sheets were as follows:



	9 Months Ended
	September 30,
	2016			2015
	(in millions)
AROs at beginning of year	$	0.6		$	0.6
Accretion	0.7			—
Revisions in estimated cash flows	75.1			—
Liabilities settled	(0.3		)	—
AROs at end of period	$	76.1		$	0.6