BASIS OF PRESENTATION, CONSOLIDATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Foreign Currency Exposure (Details)	Dec. 31, 2017	Dec. 31, 2016
One British pound sterling into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.35	1.24
One British pound sterling into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.35	1.24
One euro into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.20	1.05
One euro into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.20	1.05
One Australian dollar into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.78	0.72
One Australian dollar into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.78	0.72
One Norwegian kroner into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1223	0.1162
One Norwegian kroner into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1223	0.1162
One Nigerian naira into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0028	0.0032
One Nigerian naira into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0028	0.0032
High | One British pound sterling into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.35	1.30
High | One British pound sterling into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.36	1.48
High | One euro into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.20	1.12
High | One euro into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.20	1.15
High | One Australian dollar into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.79	0.77
High | One Australian dollar into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.81	0.78
High | One Norwegian kroner into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1269	0.1253
High | One Norwegian kroner into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1294	0.1253
High | One Nigerian naira into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0028	0.0032
High | One Nigerian naira into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0033	0.0050
Average | One British pound sterling into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.33	1.24
Average | One British pound sterling into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.31	1.33
Average | One euro into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.18	1.08
Average | One euro into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.15	1.11
Average | One Australian dollar into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.77	0.75
Average | One Australian dollar into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.77	0.75
Average | One Norwegian kroner into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1225	0.1193
Average | One Norwegian kroner into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1219	0.1202
Average | One Nigerian naira into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0028	0.0032
Average | One Nigerian naira into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0030	0.0037
Low | One British pound sterling into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.31	1.21
Low | One British pound sterling into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.24	1.21
Low | One euro into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.16	1.04
Low | One euro into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	1.06	1.04
Low | One Australian dollar into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.75	0.72
Low | One Australian dollar into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.74	0.72
Low | One Norwegian kroner into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1193	0.1145
Low | One Norwegian kroner into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.1152	0.1145
Low | One Nigerian naira into U.S. dollars | Quarter To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0028	0.0031
Low | One Nigerian naira into U.S. dollars | Year To Date
Schedule of Foreign Currency [Line Items]
Foreign currency exchange rates	0.0027	0.0029