Supplemental Cash Flow Information - Schedule of Supplemental Non-Cash Transaction and Nonmonetary Exchange Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Supplemental Non-cash Transactions:
Capital expenditures incurred but not paid at June 30	$ 1,506	$ 2,536
Property acquired under capital leases	1,078
Additions to ARO asset	$ 186	$ 141