Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligations [Abstract]

Schedule of Change in the Liability for the Asset Retirement Obligations

The following table summarizes the change in the liability for the AROs (in thousands):

	Amount
Balance, December 31, 2015	$	2,446
Additional asset retirement obligations incurred		447
Liabilities settled		(53)
Accretion expense		236
Balance, December 31, 2016		3,076
Additional asset retirement obligations incurred		468
Liabilities settled		(206)
Accretion expense		238
Balance, December 31, 2017	$	3,576