Lease Accounting (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) mi	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Lessor, Lease, Description [Line Items]
Operating lease costs	$ 27,200
Operating rent expense		$ 30,800	$ 36,900
Mileage Credits	$ 24,800	26,200	8,400
Number of miles of pipe leased as lessor | mi	86
Fair value of direct finance lease, current	$ 9,300
Fixed lease payments per year	$ 5,200
Fixed lease interest rate per year	10.25%
Current portion of net investments in direct finance leases		8,400
Marine Transportation
Lessor, Lease, Description [Line Items]
Lease revenue	$ 27,000
Operating Leases, Income Statement, Lease Revenue		27,000	25,100
Onshore facilities and transportation
Lessor, Lease, Description [Line Items]
Lease revenue	6,100
Operating Leases, Income Statement, Lease Revenue		$ 6,600	$ 5,200
Fair value of direct finance lease, current	$ 116,996