v2.4.0.6
Debt (Details 4) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Reduction to interest expense due to periodic settlements of active swap agreements      
Interest expense $ 440.2 $ 507.4 $ 595.9
Reduction to interest expense due to periodic settlements of active swap agreements [Member]
     
Reduction to interest expense due to periodic settlements of active swap agreements      
Interest expense $ 5.4 $ 8.5 $ 8.7