Fair Value of Financial Instruments (Schedule Of Fair Values Of Selected Financial Instruments Measured On A Non-Recurring Basis) (Details) (Unsecured Debt [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Senior Notes [Member] | 4.875% Senior Notes [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Debt instrument, interest rate	4.875%
Fair Value, Measurements, Non-Recurring [Member] | 2009 Convertible Notes [Member] | Carrying Amount [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Convertible notes	$ 3.0	$ 12.6
Fair Value, Measurements, Non-Recurring [Member] | 2009 Convertible Notes [Member] | Fair Value [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Convertible notes	5.9	26.6
Fair Value, Measurements, Non-Recurring [Member] | 2011 Convertible Notes [Member] | Carrying Amount [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Convertible notes	97.0	198.3
Fair Value, Measurements, Non-Recurring [Member] | 2011 Convertible Notes [Member] | Fair Value [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Convertible notes	192.1	428.3
Fair Value, Measurements, Non-Recurring [Member] | Senior Notes [Member] | 4.875% Senior Notes [Member] | Carrying Amount [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Senior notes	400.0	400.0
Fair Value, Measurements, Non-Recurring [Member] | Senior Notes [Member] | 4.875% Senior Notes [Member] | Fair Value [Member]
Fair Value, Selected Financial Instruments Measured on A Recurring and Non-Recurring Basis [Line Items]
Senior notes	$ 377.0	$ 380.0