Income Taxes, Income Tax Examination (Details) (USD $) In Millions, unless otherwise specified				6 Months Ended
	Jun. 30, 2013 Internal Revenue Service (IRS) [Member]	Jan. 31, 2013 Internal Revenue Service (IRS) [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member]	Jun. 30, 2013 Minimum [Member] Internal Revenue Service (IRS) [Member]	Jun. 30, 2013 Minimum [Member] State and Local Jurisdiction [Member]	Jun. 30, 2013 Maximum [Member] Internal Revenue Service (IRS) [Member]	Jun. 30, 2013 Maximum [Member] State and Local Jurisdiction [Member]
Income Tax Examination [Line Items]
Tax years that remain subject to examination				2007	2002	2012	2011
Summary of income tax examinations [Abstract]
Deposits with the IRS			$ 60.4
Deposits with the IRS remaining to offset tax and interest liabilities			43.5
Refund adjustment from settlement with taxing authority		42.3
Income tax years currently under examination				2010		2012
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound	$ (0.7)