Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies, Environmental Liabilities (Details)

v3.6.0.2
Commitments and Contingencies, Environmental Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Accrued Environmental Obligations [Abstract]    
Discounted environmental liabilities $ 43,681 $ 43,526
Undiscounted environmental liabilities 1,955 2,836
Total accrued environmental liabilities $ 45,636 $ 46,362