Asset Retirement Obligations

12 Months Ended

Dec. 31, 2016

Asset Retirement Obligation [Abstract]

Asset retirement obligations

Asset Retirement Obligations

The Company records obligations related to retirement costs of natural gas distribution mains and lines, natural gas transmission lines, storage facilities, decommissioning of certain electric generating facilities, reclamation of certain aggregate properties, special handling and disposal of hazardous materials at certain electric generating facilities, natural gas distribution facilities and buildings, and certain other obligations as asset retirement obligations.

A reconciliation of the Company's liability, which is included in other accrued liabilities and deferred credits and other liabilities - other on the Consolidated Balance Sheets, for the years ended December 31 was as follows:

	2016			2015
	(In thousands)
Balance at beginning of year	$	242,224		$	27,211
Liabilities incurred	15,114			2,751
Liabilities settled	(4,338		)	(1,708		)
Accretion expense	13,918			2,134
Revisions in estimates	48,052			211,836
Balance at end of year	$	314,970		$	242,224

The 2016 revisions in estimates consist principally of updated asset retirement obligation costs associated with natural gas transmission lines and storage facilities at the pipeline and midstream segment. The 2015 revisions in estimates consist principally of updated asset retirement obligation costs associated with natural gas distribution mains and lines at the natural gas distribution segment.

The Company believes that largely all expenses related to asset retirement obligations at the Company's regulated operations will be recovered in rates over time and, accordingly, defers such expenses as regulatory assets. For more information on the Company's regulatory assets and liabilities, see Note 4.