Summary of Significant Accounting Policies Cash and Cash Equivalents (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Abstract]
Cash paid for interest, net of capitalized interest	$ 105.1	$ 90.5	$ 80.2
Cash paid (received) for income taxes	30.0	(28.5)	14.0
Change in capital expenditure accrual balance	$ 88.5	$ 14.7	$ 16.9