SEGMENT INFORMATION Revenue and Long Lived Assets by Country (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2018 USD ($) Country	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2018 USD ($) Customer Country	Mar. 31, 2017 USD ($) Customer	Mar. 31, 2016 USD ($) Customer
Segment Reporting Information [Line Items]
Revenues	$ 358,442	$ 360,735	$ 373,676	$ 352,109	$ 336,194	$ 337,443	$ 357,467	$ 369,398	$ 1,444,962	$ 1,400,502	$ 1,715,513
Long-Lived Assets	2,068,020				2,254,364				2,068,020	2,254,364
Construction in Progress, Gross	$ 67,710				199,275				$ 67,710	$ 199,275
Number of Countries in which Entity Operates | Country	10								10
Customer Concentration Risk | Sales Revenue, Net
Segment Reporting Information [Line Items]
Concentration Risk, Percentage									61.00%
Number Of Other Clients Over 10% In Any Of The Three Comparative Years | Customer									1	1	2
External customer
Segment Reporting Information [Line Items]
Revenues									$ 1,444,962	$ 1,400,502	$ 1,715,513
U.K.
Segment Reporting Information [Line Items]
Revenues									530,948	510,796	587,493
Long-Lived Assets	$ 630,555				600,948				630,555	600,948
Australia
Segment Reporting Information [Line Items]
Revenues									199,264	216,562	272,407
Long-Lived Assets	226,085				317,944				226,085	317,944
Nigeria
Segment Reporting Information [Line Items]
Revenues									195,681	204,521	246,449
Long-Lived Assets	293,781				228,863				293,781	228,863
United States
Segment Reporting Information [Line Items]
Revenues									103,047	87,234	158,901
Long-Lived Assets	410,651				298,804				410,651	298,804
Canada
Segment Reporting Information [Line Items]
Revenues									61,701	61,877	61,257
Long-Lived Assets	193,092				204,842				193,092	204,842
Norway
Segment Reporting Information [Line Items]
Revenues									258,878	218,848	225,807
Long-Lived Assets	156,593				268,892				156,593	268,892
Falkland Islands
Segment Reporting Information [Line Items]
Revenues									0	1,935	44,724
Trinidad
Segment Reporting Information [Line Items]
Revenues									53,144	57,531	55,423
Long-Lived Assets	80,497				118,058				80,497	118,058
Other countries
Segment Reporting Information [Line Items]
Revenues									42,299	41,198	$ 63,052
Long-Lived Assets	$ 9,056				$ 16,738				$ 9,056	$ 16,738