Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Debt
Debt payable within one year	$ 59.1	$ 57.9
Debt payable after one year	3.0	3.3
Debt Subject to Compromise
Bank borrowings	500.0	500.0
Accrued interest on bank borrowings	414.6	407.3
Drawn letters of credit	26.3	26.3
Accrued interest on drawn letters of credit	8.6	8.2
Debt Subject to Compromise	$ 949.5	$ 941.8
Weighted average interest rates on total debt (as a percent)	3.50%	3.50%