Operating Segment Information (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Operating Income (Loss) by Operating Segment
Revenue	$ 96,911	$ 92,782	$ 178,200	$ 177,433
Direct operating expenses	46,908	42,658	91,225	85,727
Drydock expense	3,683	6,159	10,207	13,123
General and administrative expenses	10,910	11,456	22,333	23,187
Depreciation and amortization	14,982	13,977	29,658	27,952
(Gain) loss on sale of assets		106	10	106
Impairment Charge		97,665		97,665
Operating income (loss)	20,428	(79,239)	24,767	(70,327)
North Sea [Member]
Operating Income (Loss) by Operating Segment
Revenue	43,836	37,217	79,235	72,492
Direct operating expenses	20,727	19,299	41,441	39,465
Drydock expense	2,371	1,489	5,441	3,519
General and administrative expenses	2,689	2,700	5,923	5,521
Depreciation and amortization	4,970	4,624	9,757	9,284
Operating income (loss)	13,079	9,105	16,673	14,703
Southeast Asia [Member]
Operating Income (Loss) by Operating Segment
Revenue	15,678	16,841	31,213	32,668
Direct operating expenses	2,887	2,385	5,749	4,710
Drydock expense	1,755	1,637	1,940	3,583
General and administrative expenses	761	763	1,435	1,362
Depreciation and amortization	2,431	2,036	4,882	4,001
Operating income (loss)	7,844	10,020	17,207	19,012
Americas [Member]
Operating Income (Loss) by Operating Segment
Revenue	37,397	38,724	67,752	72,273
Direct operating expenses	23,294	20,974	44,035	41,552
Drydock expense	(443)	3,033	2,826	6,021
General and administrative expenses	1,930	2,361	4,199	4,547
Depreciation and amortization	7,132	7,084	14,238	14,212
(Gain) loss on sale of assets		109	10	109
Impairment Charge		97,665		97,665
Operating income (loss)	5,484	(92,502)	2,444	(91,833)
Other [Member]
Operating Income (Loss) by Operating Segment
General and administrative expenses	5,530	5,632	10,776	11,757
Depreciation and amortization	449	233	781	455
(Gain) loss on sale of assets		(3)		(3)
Operating income (loss)	$ (5,979)	$ (5,862)	$ (11,557)	$ (12,209)