Lease Accounting (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) mi	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) mi	Sep. 30, 2018 USD ($)
Lessor, Lease, Description [Line Items]
Operating lease costs	$ 13,000		$ 39,200
Number of miles of pipe leased as lessor | mi	86		86
Fixed quarterly payments to be received under finance lease arrangement	$ 5,200		$ 5,200
Interest rate under finance lessor arrangement			10.25%
Fair value of direct finance lease, current	9,100		$ 9,100
Marine Transportation
Lessor, Lease, Description [Line Items]
Lease revenue	6,800	$ 6,800	20,200	$ 20,200
Onshore Facilities & Transportation
Lessor, Lease, Description [Line Items]
Lease revenue	1,300	$ 1,600	4,200	$ 4,700
Fair value of direct finance lease, current	$ 119,161		$ 119,161