Annual report pursuant to Section 13 and 15(d)

Property and Equipment - Schedule of Asset Retirement Obligation (Details)

v3.6.0.2
Property and Equipment - Schedule of Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset retirement obligation, beginning of period $ 26,437 $ 17,938  
Liabilities incurred 10,971 8,800 $ 9,295
Liabilities settled (4,189) (1,121)  
Accretion expense 1,057 820 761
Asset retirement obligation as of end of period 34,276 26,437 $ 17,938
Less current portion 195 75  
Asset retirement obligation, long-term $ 34,081 $ 26,362