Consolidating Financial Statements Text (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	October 2007
Debt Instrument, Face Amount	$ 300.0
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Debt Instrument, Maturity Date, Description	2012
Senior Exchangeable Notes due 2015 at a fixed interest rate of 4.50% [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	August 2009
Debt Instrument, Face Amount	172.5
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Debt Instrument, Maturity Date, Description	2015
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	March 2012
Debt Instrument, Face Amount	$ 325.0
Debt Instrument, Interest Rate, Stated Percentage	3.75%
Debt Instrument, Maturity Date, Description	2022