Note 12 - Operating Segment Information (Details Textual) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Marine Services Revenue		$ 26,617	$ 27,821	$ 30,487	$ 38,794	$ 50,585	$ 60,668	$ 74,461	$ 89,092	$ 123,719	$ 274,806	$ 495,769
Long-Lived Assets	[1]	995,220				1,266,486				995,220	1,266,486	1,500,418	[2]
UNITED STATES
Marine Services Revenue										28,500	73,400	152,000
Long-Lived Assets		$ 371,600				$ 431,700				$ 371,600	$ 431,700	$ 519,800

[1] Vessels under construction are included in other assets until delivered. Revenue, long-lived assets and capital expenditures presented in the table above are allocated to segments based on the location where the vessel is employed, which in some instances differs from the segment where the vessel is legally owned. In 2016, we had $28.5 million in revenue and $371.6 million in long-lived assets attributed to the United States, our country of domicile. In 2015, we had $73.4 million in revenue and $431.7 million in long-lived assets attributed to the United States. In 2014, we had $152.0 million in revenue and $519.8 million in long-lived assets attributed to the United States.

[2] Goodwill is included in the North Sea segment.