Other Noncurrent Liabilities

12 Months Ended

Dec. 31, 2017

Other Liabilities Disclosure [Abstract]

Other noncurrent liabilities consisted of the following:



	December 31, 2017		December 31, 2016
	(in millions)
Accrued straight-line rent	$	13	$	10
Reserve for underground storage tank removal	41		34
Reserve for environmental remediation, long-term	23		35
Unfavorable lease liability	10		12
Aloha acquisition contingent consideration	15		15
Others	23		10
Total	$	125	$	116

We record an asset retirement obligation for the estimated future cost to remove underground storage tanks. Revisions to the liability could occur due to changes in tank removal costs, tank useful lives or if federal and/or state regulators enact new guidance on the removal of such tanks. Changes in the carrying amount of asset retirement obligations for the years ended December 31, 2017 and 2016 were as follows:



	Year Ended December 31,
	2017			2016
	(in millions)
Balance at beginning of year	$	34		$	34
Liabilities incurred	3			3
Liabilities settled	(2		)	(1		)
Accretion expense	6			4
Revision of estimated cash flows	—			(6		)
Balance at end of year	$	41		$	34