Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2012 Federal	Dec. 31, 2012 Federal
Income Tax Disclosure
Effective income tax rate	37.40%	28.90%
Federal income tax refund received			$ 59.9	$ 71.4