Operating Segment Information (Details) (USD $) In Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Jun. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Operating Income (Loss) by Operating Segment
Revenue	$ 103,778	$ 94,479		$ 281,978	$ 271,912
Direct operating expenses	48,103	41,729		139,328	127,456
Drydock expense	5,726	7,242		15,933	20,365
General and administrative expenses	11,859	10,236		34,192	33,423
Depreciation and amortization expense	14,896	14,492		44,554	42,444
(Gain) loss on sale of assets		(5,201)		10	(5,095)
Impairment charge			97,700		97,665
Operating income (loss)	23,194	25,981		47,961	(44,346)
North Sea [Member]
Operating Income (Loss) by Operating Segment
Revenue	49,176	38,340		128,411	110,832
Direct operating expenses	20,999	19,105		62,440	58,570
Drydock expense	2,999	3,614		8,440	7,133
General and administrative expenses	3,195	2,485		9,118	8,006
Depreciation and amortization expense	4,924	4,704		14,681	13,988
(Gain) loss on sale of assets		(5,246)			(5,246)
Operating income (loss)	17,059	13,678		33,732	28,381
Southeast Asia [Member]
Operating Income (Loss) by Operating Segment
Revenue	16,660	17,867		47,873	50,535
Direct operating expenses	3,409	3,204		9,158	7,914
Drydock expense	2,023	488		3,963	4,071
General and administrative expenses	762	633		2,197	1,995
Depreciation and amortization expense	2,427	2,463		7,309	6,464
Operating income (loss)	8,039	11,079		25,246	30,091
Americas [Member]
Operating Income (Loss) by Operating Segment
Revenue	37,942	38,272		105,694	110,545
Direct operating expenses	23,695	19,420		67,730	60,972
Drydock expense	704	3,140		3,530	9,161
General and administrative expenses	2,005	1,533		6,204	6,080
Depreciation and amortization expense	7,078	7,016		21,316	21,228
(Gain) loss on sale of assets		45		10	154
Impairment charge					97,665
Operating income (loss)	4,460	7,118		6,904	(84,715)
Other [Member]
Operating Income (Loss) by Operating Segment
General and administrative expenses	5,897	5,585		16,673	17,342
Depreciation and amortization expense	467	309		1,248	764
(Gain) loss on sale of assets					(3)
Operating income (loss)	$ (6,364)	$ (5,894)		$ (17,921)	$ (18,103)