Commitments And Contingencies And Other Matters - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Commitments And Contingencies [Line Items]
Total investment	$ 2,721,339	$ 2,695,772
Q7000 [Member]
Commitments And Contingencies [Line Items]
Total investment	$ 306,700
Q7000 [Member] | Contract Signing
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 [Member] | Due 2016
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 [Member] | Due December 2017
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 [Member] | Due December 31, 2018
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 [Member] | Vessel Delivery
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Shipyard In Singapore | Q7000 [Member]
Commitments And Contingencies [Line Items]
Total investment	$ 207,600