Intangible Assets (Schedule of Components of Intangible Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 219,456	$ 230,908
Accumulated Amortization	76,741	68,306
Carrying Value	142,715	162,602
Intangibles associated with lease | Onshore Facilities & Transportation
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	13,260
Accumulated Amortization	0	5,407
Carrying Value	0	7,853
Contract intangibles | Marine Transportation
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	27,800	27,800
Accumulated Amortization	21,674	17,593
Carrying Value	6,126	10,207
Contract intangibles | Offshore pipeline transportation
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	158,101	158,101
Accumulated Amortization	34,671	28,431
Carrying Value	123,430	129,670
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	33,555	31,747
Accumulated Amortization	20,396	16,875
Carrying Value	$ 13,159	$ 14,872