Note 9 - Operating Segment Information (Details) - Operating Income (Loss) by Operating Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Revenue	$ 128,686	$ 121,802	$ 379,651	$ 330,038
Direct operating expenses	62,230	55,201	178,253	161,690
Drydock expense	4,353	2,444	16,249	20,178
General and administrative expenses	15,021	13,522	46,913	41,217
Depreciation and amortization expense	19,168	16,252	56,729	46,447
Impairment charge			7,459
Gain on sale of assets and other	(6,877)	(6,001)	(6,877)	(5,875)
Operating income (loss)	34,791	40,384	80,925	66,381
North Sea [Member]
Segment Reporting Information [Line Items]
Revenue	61,781	51,098	172,658	134,423
Direct operating expenses	29,557	24,225	85,500	71,098
Drydock expense	1,357	2,078	5,406	7,663
General and administrative expenses	3,743	3,623	12,997	10,417
Depreciation and amortization expense	8,371	6,206	24,628	16,315
Impairment charge			7,015
Gain on sale of assets and other		(6,105)		(6,107)
Operating income (loss)	18,753	21,071	37,112	35,037
Southeast Asia [Member]
Segment Reporting Information [Line Items]
Revenue	13,930	18,782	49,665	45,156
Direct operating expenses	6,224	6,104	17,103	18,225
Drydock expense	554	(947)	4,047	5,303
General and administrative expenses	1,434	1,505	4,200	4,456
Depreciation and amortization expense	2,708	2,885	8,503	8,537
Impairment charge			444
Gain on sale of assets and other	(5,520)		(5,520)	82
Operating income (loss)	8,530	9,235	20,888	8,553
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	52,975	51,922	157,328	150,459
Direct operating expenses	26,449	24,872	75,650	72,367
Drydock expense	2,442	1,313	6,796	7,212
General and administrative expenses	3,076	2,845	9,416	8,068
Depreciation and amortization expense	7,403	6,605	21,415	19,889
Gain on sale of assets and other	(1,357)	102	(1,357)	110
Operating income (loss)	14,962	16,185	45,408	42,813
Other [Member]
Segment Reporting Information [Line Items]
General and administrative expenses	6,768	5,549	20,300	18,276
Depreciation and amortization expense	686	556	2,183	1,706
Gain on sale of assets and other		2		40
Operating income (loss)	$ (7,454)	$ (6,107)	$ (22,483)	$ (20,022)