Intangible Assets (Schedule Of Components Of Intangible Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 395,939	$ 395,692
Accumulated Amortization	202,550	190,805
Carrying Value	193,389	204,887
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	94,654	94,654
Accumulated Amortization	91,125	89,756
Carrying Value	3,529	4,898
Licensing agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	38,678	38,678
Accumulated Amortization	35,366	34,204
Carrying Value	3,312	4,474
Segment total
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	133,332	133,332
Accumulated Amortization	126,491	123,960
Carrying Value	6,841	9,372
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	35,430	35,430
Accumulated Amortization	34,379	33,676
Carrying Value	1,051	1,754
Intangibles associated with lease
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	13,260	13,260
Accumulated Amortization	4,696	4,459
Carrying Value	8,564	8,801
Segment total
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	48,690	48,690
Accumulated Amortization	39,075	38,135
Carrying Value	9,615	10,555
Marine contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	27,000	27,000
Accumulated Amortization	9,000	6,300
Carrying Value	18,000	20,700
Offshore pipeline contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	158,101	158,101
Accumulated Amortization	15,949	11,788
Carrying Value	142,152	146,313
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	28,816	28,569
Accumulated Amortization	12,035	10,622
Carrying Value	$ 16,781	$ 17,947