Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 253.1	$ 219.7	$ 188.0
Other comprehensive income (loss):
Unrealized gain on cash flow hedge, net of tax $(0.1) for 2011			0.1
Unrealized loss on securities, net of tax of $0.1 for 2012	(0.1)	(0.1)
Other comprehensive income (loss)	(0.1)	(0.1)	0.1
Comprehensive income	$ 253.0	$ 219.6	$ 188.1