Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation expense related to property and equipment			$ 218,107	$ 202,519	$ 183,808
Accrued capital expenditures			10,000	2,700
Asset impairment charges	$ 13,900	$ 49,400	13,892	49,375	$ 58,057
Marine Operation Assets | Held-for-Sale
Property, Plant and Equipment [Line Items]
Estimated fair value of assets in the process of being sold	$ 6,300	$ 14,000	$ 6,300	$ 14,000