Income Taxes (Schedule Of Income Tax Provision) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Income before provision for income taxes	$ 91.3	$ 83.8	$ 89.2	$ 78.8	$ 79.8	$ 78.7	$ 70.7	$ 67.2	$ 343.1	$ 296.4	$ 253.5
Current provision (benefit) for income taxes, Federal									94.9	87.7	66.2
Current provision (benefit) for income taxes, State									3.5	6.3	3.7
Current provision (benefit) for income taxes									98.4	94.0	69.9
Deferred provision (benefit) for income taxes, Federal									23.6	13.3	16.7
Deferred provision (benefit) for income taxes, State									1.4	2.0	(2.8)
Deferred provision (benefit) for income taxes									25.0	15.3	13.9
Interest										(0.7)	(0.2)
Penalties										(0.2)	(0.2)
Interest and penalties benefit										(0.9)	(0.4)
Provision for income taxes									$ 123.4	$ 108.4	$ 83.4