Note 10 - Operating Segment Information (Details) - Operating Income (Loss) by Operating Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenue	$ 121,802	$ 101,867	$ 330,038	$ 294,186
Direct operating expenses	55,201	48,778	161,690	146,433
Drydock expense	2,444	9,515	20,178	23,350
General and administrative expenses	13,522	14,389	41,217	38,501
Depreciation and amortization expense	16,252	14,697	46,447	44,576
Gain on sale of assets	(6,001)	(3,919)	(5,875)	(8,744)
Operating income (loss)	40,384	17,548	66,381	49,211
Quarter Ended September 30, 2012
Impairment Charge		859		859
North Sea [Member]
Segment Reporting Information [Line Items]
Revenue	51,098	41,757	134,423	124,796
Direct operating expenses	24,225	20,938	71,098	61,617
Drydock expense	2,078	2,095	7,663	7,879
General and administrative expenses	3,623	3,743	10,417	10,798
Depreciation and amortization expense	6,206	4,742	16,315	14,252
Gain on sale of assets	(6,105)		(6,107)
Operating income (loss)	21,071	9,380	35,037	29,391
Quarter Ended September 30, 2012
Impairment Charge		859		859
Southeast Asia [Member]
Segment Reporting Information [Line Items]
Revenue	18,782	17,633	45,156	46,899
Direct operating expenses	6,104	4,147	18,225	12,697
Drydock expense	(947)	2,200	5,303	4,329
General and administrative expenses	1,505	677	4,456	2,239
Depreciation and amortization expense	2,885	2,684	8,537	7,874
Gain on sale of assets	0		82
Operating income (loss)	9,235	7,925	8,553	19,760
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	51,922	42,477	150,459	122,491
Direct operating expenses	24,872	23,693	72,367	72,119
Drydock expense	1,313	5,220	7,212	11,142
General and administrative expenses	2,845	2,581	8,068	7,700
Depreciation and amortization expense	6,605	6,704	19,889	20,733
Gain on sale of assets	102	(3,919)	110	(8,744)
Operating income (loss)	16,185	8,198	42,813	19,541
Other [Member]
Segment Reporting Information [Line Items]
Revenue	0		0
Direct operating expenses	0		0
Drydock expense	0		0
General and administrative expenses	5,549	7,388	18,276	17,764
Depreciation and amortization expense	556	567	1,706	1,717
Gain on sale of assets	2		40
Operating income (loss)	$ (6,107)	$ (7,955)	$ (20,022)	$ (19,481)