Intangible Assets (Schedule of Components of Intangible Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 395,870	$ 395,692
Accumulated Amortization	208,429	190,805
Carrying Value	187,441	204,887
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	94,654	94,654
Accumulated Amortization	91,809	89,756
Carrying Value	2,845	4,898
Licensing agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	38,678	38,678
Accumulated Amortization	35,947	34,204
Carrying Value	2,731	4,474
Segment total
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	133,332	133,332
Accumulated Amortization	127,756	123,960
Carrying Value	5,576	9,372
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	35,430	35,430
Accumulated Amortization	34,731	33,676
Carrying Value	699	1,754
Intangibles associated with lease
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	13,260	13,260
Accumulated Amortization	4,815	4,459
Carrying Value	8,445	8,801
Segment total
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	48,690	48,690
Accumulated Amortization	39,546	38,135
Carrying Value	9,144	10,555
Marine contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	27,000	27,000
Accumulated Amortization	10,350	6,300
Carrying Value	16,650	20,700
Offshore pipeline contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	158,101	158,101
Accumulated Amortization	18,029	11,788
Carrying Value	140,072	146,313
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	28,747	28,569
Accumulated Amortization	12,748	10,622
Carrying Value	$ 15,999	$ 17,947