Condensed Consolidating Financial Data (Condensed Consolidating Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Condensed Financial Statements, Captions [Line Items]
Current assets	$ 3,493.5	$ 3,370.8
Non-current assets	3,623.2	3,722.2
Total assets	7,116.7	7,093.0
Current liabilities	1,463.7	1,677.2
Non-current liabilities	3,741.0	3,595.3
Stockholders' equity	1,912.0	1,820.5	1,766.8	1,384.2
Total liabilities and stockholders' equity	7,116.7	7,093.0
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	359.0	314.6
Investment in subsidiaries	5,688.8	5,340.3
Non-current assets	114.5	153.7
Total assets	6,162.3	5,808.6
Current liabilities	260.8	217.4
Non-current liabilities	3,989.5	3,770.7
Stockholders' equity	1,912.0	1,820.5
Total liabilities and stockholders' equity	6,162.3	5,808.6
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	995.9	998.6
Investment in subsidiaries	1,748.1	1,739.8
Non-current assets	4,003.9	3,768.8
Total assets	6,747.9	6,507.2
Current liabilities	589.0	588.5
Non-current liabilities	507.0	504.3
Stockholders' equity	5,651.9	5,414.4
Total liabilities and stockholders' equity	6,747.9	6,507.2
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	2,140.0	2,067.6
Investment in subsidiaries		93.4
Non-current assets	914.0	1,015.1
Total assets	3,054.0	3,176.1
Current liabilities	614.1	878.0
Non-current liabilities	654.9	539.0
Stockholders' equity	1,785.0	1,759.1
Total liabilities and stockholders' equity	3,054.0	3,176.1
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	(1.4)	(10.0)
Investment in subsidiaries	(7,436.9)	(7,173.5)
Non-current assets	(1,409.2)	(1,215.4)
Total assets	(8,847.5)	(8,398.9)
Current liabilities	(0.2)	(6.7)
Non-current liabilities	(1,410.4)	(1,218.7)
Stockholders' equity	(7,436.9)	(7,173.5)
Total liabilities and stockholders' equity	$ (8,847.5)	$ (8,398.9)