Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Financial Instruments (Details Textual)

v2.4.0.6
Fair Value of Financial Instruments (Details Textual) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Jun. 30, 2012
Fair Value Inputs Level2 [Member]
Dec. 31, 2011
Fair Value Inputs Level2 [Member]
Dec. 31, 2011
Fair Value Inputs Level3 [Member]
Dec. 31, 2011
US Drilling Segment [Member]
Fair Value of Financial Instruments (Textual) [Abstract]        
Carrying amount of interest rate swap agreements $ 0.1 $ 0.1    
Non-cash pre-tax impairment charge       170.0
Non-cash pre-tax impairment charge after tax       109.1
Fair value       $ 169.5
Percentage of discount on expected future cash flows     10.00%