Asset Retirement Obligation (Tables)

12 Months Ended

Dec. 31, 2015

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligation

Activity related to the Company's asset retirement obligations is as follows:

(In thousands)	Year Ended   December 31, 2015
Balance at beginning of period	$	126,655
Liabilities incurred	12,235
Liabilities settled	(175		)
Accretion expense	6,891
Balance at end of period	$	145,606