Fair Value (Available-For-Sale Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value Disclosure [Line Items]
Amortized Cost	$ 135.3	$ 121.8
Gross Unrealized Gains	1.1	1.4
Gross Unrealized Losses	(1.2)	(1.8)
Fair Value	135.2	121.4
Government [Member]
Fair Value Disclosure [Line Items]
Amortized Cost	34.3	30.3
Gross Unrealized Gains	0.2	0.3
Gross Unrealized Losses	(0.3)	(0.5)
Fair Value	34.2	30.1
Corporate/Other Bonds [Member]
Fair Value Disclosure [Line Items]
Amortized Cost	101.0	91.5
Gross Unrealized Gains	0.9	1.1
Gross Unrealized Losses	(0.9)	(1.3)
Fair Value	$ 101.0	$ 91.3