Commitments And Contingencies And Other Matters - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Commitments And Contingencies [Line Items]
Total investment	$ 2,805,043	$ 2,785,778
Siem Helix 1 and Siem Helix 2
Commitments And Contingencies [Line Items]
Term of charter agreement	7 years
Q7000
Commitments And Contingencies [Line Items]
Total investment	$ 427,400
Q7000 | Contract Signing
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 | Due 2016
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 | Due 2017
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 | Due 2018
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 | Vessel Delivery
Commitments And Contingencies [Line Items]
Percentage of contract price	20.00%
Q7000 | Shipyard
Commitments And Contingencies [Line Items]
Total investment	$ 276,800