Income Taxes (Components of Income Tax Expense) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income tax expense	$ 6.0	$ 7.7
Deferred income taxes	23.3	(9.2)
Parent Company [Member]
Income tax expense	$ 6.0	$ 7.7