Note 9 - Operating Segment Information (Details) - Operating Income (Loss) by Operating Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Revenue	$ 131,365	$ 111,348	$ 250,965	$ 208,236
Direct operating expenses	59,724	53,352	116,023	106,489
Drydock expense	4,685	9,174	11,896	17,734
General and administrative expenses	17,403	16,745	31,892	27,695
Depreciation and amortization expense	19,204	15,025	37,561	30,195
Impairment charge	7,459		7,459
Operating income (loss)	22,890	16,926	46,134	25,997
Quarter Ended June 30, 2013
(Gain) loss on sale of assets		126		126
North Sea [Member]
Segment Reporting Information [Line Items]
Revenue	58,254	42,703	110,877	83,325
Direct operating expenses	29,214	23,676	55,943	46,873
Drydock expense	1,381	3,002	4,049	5,585
General and administrative expenses	5,762	3,490	9,254	6,794
Depreciation and amortization expense	8,434	5,015	16,257	10,109
Impairment charge	7,015		7,015
Operating income (loss)	6,448	7,522	18,359	13,966
Quarter Ended June 30, 2013
(Gain) loss on sale of assets		(2)		(2)
Southeast Asia [Member]
Segment Reporting Information [Line Items]
Revenue	17,431	16,636	35,735	26,374
Direct operating expenses	5,395	5,976	10,879	12,121
Drydock expense	1,940	3,144	3,493	6,250
General and administrative expenses	1,404	1,684	2,766	2,951
Depreciation and amortization expense	2,899	2,845	5,795	5,652
Impairment charge	444		444
Operating income (loss)	5,349	2,905	12,358	(682)
Quarter Ended June 30, 2013
(Gain) loss on sale of assets		82		82
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	55,680	52,009	104,353	98,537
Direct operating expenses	25,115	23,700	49,201	47,495
Drydock expense	1,364	3,028	4,354	5,899
General and administrative expenses	3,223	2,781	6,340	5,223
Depreciation and amortization expense	7,206	6,611	14,012	13,284
Operating income (loss)	18,772	15,881	30,446	26,628
Quarter Ended June 30, 2013
(Gain) loss on sale of assets		8		8
Other [Member]
Segment Reporting Information [Line Items]
General and administrative expenses	7,014	8,790	13,532	12,727
Depreciation and amortization expense	665	554	1,497	1,150
Operating income (loss)	(7,679)	(9,382)	(15,029)	(13,915)
Quarter Ended June 30, 2013
(Gain) loss on sale of assets		$ 38		$ 38