Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Mar. 31, 2017
Schedule Of Equity Method Investments [Line Items]
Prepaid expenses and other current assets	$ 75,819	$ 79,838
Accumulated deficit in joint ventures	17,016	$ 17,016
TerraSea Environmental Solutions [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%
Prepaid expenses and other current assets	24,696	$ 24,703
Accumulated deficit in joint ventures	17,016	$ 17,016
Provision for losses to be assumed from joint venture	$ 2,634