v2.4.0.6
Contingencies (Details) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2009
Mar. 31, 2011
Dec. 31, 2006
Mar. 31, 2010
Sep. 30, 2009
Loss Contingencies [Line Items]          
Number of shareholder class action lawsuits   6      
Distance from original drilling location in miles 95        
Property insurance self-insured retention per occurrence   $ 50.0      
Property coverage limit for sue and labor costs - ENSCO 74   25.0      
Property coverage limit for wreckage and debris removal costs - ENSCO 74   50.0      
Annual liability coverage limit for wreckage and debris removal costs - ENSCO 74   500.0      
Minimum estimate leg and debris removal costs   21.0      
Maximum estimate leg and debris removal costs   35.0      
Liability and insurance receivable for ENSCO 74 leg removal costs   21.0      
Civil litigation claim damages for cost of repair and business interruption due to pipeline rupture         26.0
Civil litigation damages 10.0        
Liability insurance self-insured retention per occurrence   10.0      
Annual liability coverage limit for wreckage and debris removal costs   500.0      
Liability insurance self-insured retention for two occurrences   15.0      
Liability insurance self-insured retention for each occurrence thereafter   1.0      
ENSCO 69 insured value, package policy   65.0   65.0  
Packaged policy ENSCO 69 deductible   10.0   10.0  
Lawsuit for ENSCO 69 actual damages       55.0  
Minimum estimate of ENSCO 29 wreckage removal costs   5.0      
Maximum estimate of ENSCO 29 wreckage removal costs   15.0      
Property coverage limit ENSCO 29 wreckage and debris removal costs   3.8      
ENSCO 29 insurance provision     1.2    
Minimum estimate of removal costs     $ 5.0    
Initial multi-party asbestos claims   600      
Number of plaintiffs   65      
Delaware [Member]
          
Loss Contingencies [Line Items]          
Number of shareholder class action lawsuits   3      
Texas [Member]
          
Loss Contingencies [Line Items]          
Number of shareholder class action lawsuits   3      
Number Of Plaintiffs State Courts [Member]
          
Loss Contingencies [Line Items]          
Number of plaintiffs   62      
Number Of Plaintiffs U.S. District Court [Member]
          
Loss Contingencies [Line Items]          
Number of plaintiffs   3