Quarterly report pursuant to Section 13 or 15(d)

Asset Impairment (Details Textual)

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Asset Impairment (Details Textual) (US Drilling Segment [Member], USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
US Drilling Segment [Member]
 
Segment Reporting Information [Line Items]  
Non-cash pre-tax impairment charge $ 170.0
Asset Impairment charge after tax $ 109.1