XML 62 R51.htm IDEA: XBRL DOCUMENT v3.8.0.1
Supplemental Balance Sheet Information - Other Accrued Liabilities (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]    
Accrued interest $ 4,952 $ 11,726
Asset retirement obligations 3,360 5,429
Property and other taxes payable 3,279 5,638
Accrued payroll 3,636 3,385
Other 7 162
Total other accrued liabilities $ 15,234 $ 26,340