Note 10 - Operating Segment Information (Details) - Operating Income (Loss) by Operating Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Revenue	$ 111,348	$ 104,884	$ 208,236	$ 192,319
Direct operating expenses	53,352	48,846	106,489	97,655
Drydock expense	9,174	7,639	17,734	13,835
General and administrative expenses	16,745	11,996	27,695	24,112
Depreciation and amortization expense	15,025	14,850	30,195	29,879
Gain on sale of assets	126	(3,676)	126	(4,825)
Operating income (loss)	16,926	25,229	25,997	31,663
North Sea [Member]
Segment Reporting Information [Line Items]
Revenue	42,703	45,376	83,325	83,039
Direct operating expenses	23,676	20,659	46,873	40,679
Drydock expense	3,002	2,233	5,585	5,784
General and administrative expenses	3,490	3,388	6,794	7,055
Depreciation and amortization expense	5,015	4,749	10,109	9,510
Gain on sale of assets	(2)		(2)
Operating income (loss)	7,522	14,347	13,966	20,011
Southeast Asia [Member]
Segment Reporting Information [Line Items]
Revenue	16,636	15,041	26,374	29,266
Direct operating expenses	5,976	4,747	12,121	8,550
Drydock expense	3,144	(161)	6,250	2,129
General and administrative expenses	1,684	789	2,951	1,562
Depreciation and amortization expense	2,845	2,680	5,652	5,190
Gain on sale of assets	82		82
Operating income (loss)	2,905	6,986	(682)	11,835
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	52,009	44,467	98,537	80,014
Direct operating expenses	23,700	23,440	47,495	48,426
Drydock expense	3,028	5,567	5,899	5,922
General and administrative expenses	2,781	2,518	5,223	5,119
Depreciation and amortization expense	6,611	6,851	13,284	14,029
Gain on sale of assets	8	(3,676)	8	(4,825)
Operating income (loss)	15,881	9,767	26,628	11,343
Other [Member]
Segment Reporting Information [Line Items]
General and administrative expenses	8,790	5,301	12,727	10,376
Depreciation and amortization expense	554	570	1,150	1,150
Gain on sale of assets	38		38
Operating income (loss)	$ (9,382)	$ (5,871)	$ (13,915)	$ (11,526)