Asset Retirement Obligations

The Company's asset retirement obligations consist of legal requirements to remove certain of its network infrastructure at the expiration of the underlying right-of-way ("ROW") term and restoration requirements for leased facilities. The Company recognizes its estimate of the fair value of its asset retirement obligations in the period incurred in other long-term liabilities. The fair value of the asset retirement obligation is also capitalized as property, plant and equipment and then amortized over the estimated remaining useful life of the associated asset.

As a result of a strategic review of the Company's real estate portfolio in the fourth quarter of 2012, the Company completed an updated analysis and revised its estimated future cash flows of its asset retirement obligations. The analysis required estimating the probability or likelihood that the Company will be required to remove certain of its network infrastructure and restore leased properties, and the timing and amount of eventual costs. The analysis resulted in the downward revision of the Company's asset retirement obligation liability. This change in the estimated cash flows resulted in a non-cash gain of $49 million recorded within network related expenses, and depreciation expense, or $0.23 basic and diluted net loss per share.

In conjunction with its review of the ROW asset retirement obligation, the Company identified an error in its assumptions used to estimate its ROW asset retirement obligation related to the extension of the useful lives of its conduit assets effective October 1, 2011 (See Note 1 - Organization and Summary of Significant Accounting Policies). The Company recorded a non-cash benefit of approximately $21 million within network related expenses, or $0.10 basic and diluted net loss per share during the fourth quarter of 2012 for the change in the ROW term used to estimate its ROW asset retirement obligation. The reduction in the asset retirement obligations liability includes the change in estimate of the ROW term that arose in prior periods, which did not materially affect any of the Company's previously reported results of operations or financial condition, or the current period results of operations or financial condition.

In 2012, as a result of the revisions in estimated amount and timing of cash flows for asset retirement obligations, the Company reduced its asset retirement obligations liability by $73 million with an offsetting reduction to property, plant and equipment of $24 million, network related expenses of $47 million and depreciation and amortization of $2 million. The Company first reduced property, plant and equipment to the extent of the carrying amount of the related asset initially recorded when the asset retirement obligations were established. The amount of the remaining reduction to the asset retirement obligations were recorded as a reduction to depreciation expense to the extent of historical deprecation of the related asset and then to selling, general and administrative expenses.

The following table provides asset retirement obligation activity for the years ended December 31, 2014 and 2013 (dollars in millions):



	2014			2013
Asset retirement obligation at January 1	$	56		$	55
Accretion expense	8			7
Liabilities assumed in tw telecom acquisition	22			—
Liabilities settled	(7		)	(6		)
Revision in estimated cash flows	7			—
Effect of foreign currency rate change	(1		)	—
Asset retirement obligation at December 31	$	85		$	56