Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2018

Asset Retirement Obligation Disclosure [Abstract]

Reconciliation of Asset Retirement Obligations which are Included in Other Liabilities

The following table reconciles our AROs as of the dates presented, which are included in the “Other liabilities” caption on our Consolidated Balance Sheets: 

	Year Ended December 31,
	2018			2017
Balance at beginning of period	$	3,286		$	2,459
Changes in estimates	354			149
Liabilities incurred	335			118
Liabilities settled	(8		)	(139		)
Purchase of properties	385			494
Sale of properties	(310		)	—
Accretion expense	272			205
Balance at end of period	$	4,314		$	3,286