Investments (Unrealized Loss Position For Current & Noncurrent Investments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 925.6	$ 303.0
Less than 12 Months, Unrealized Losses	(40.4)	(2.7)
12 Months or More, Fair Value	108.9	0.3
12 Months or More, Unrealized Losses	(8.0)	0
Total, Fair Value	1,034.5	303.3
Total, Unrealized Losses	(48.4)	(2.7)
Current [Member] | Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	225.3	54.9
Less than 12 Months, Unrealized Losses	(7.9)	(0.2)
12 Months or More, Fair Value	22.5	0.1
12 Months or More, Unrealized Losses	(0.8)	0
Total, Fair Value	247.8	55.0
Total, Unrealized Losses	(8.7)	(0.2)
Current [Member] | U.S. government and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	4.0	10.1
Less than 12 Months, Unrealized Losses	0	0
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Total, Fair Value	4.0	10.1
Total, Unrealized Losses	0	0
Current [Member] | Obligations of states and other political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	453.5	192.1
Less than 12 Months, Unrealized Losses	(23.5)	(2.0)
12 Months or More, Fair Value	79.7	0.2
12 Months or More, Unrealized Losses	(6.8)	0
Total, Fair Value	533.2	192.3
Total, Unrealized Losses	(30.3)	(2.0)
Current [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	242.8	45.9
Less than 12 Months, Unrealized Losses	(9.0)	(0.5)
12 Months or More, Fair Value	6.7	0
12 Months or More, Unrealized Losses	(0.4)	0
Total, Fair Value	249.5	45.9
Total, Unrealized Losses	(9.4)	(0.5)
Noncurrent [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	25.4
Less than 12 Months, Unrealized Losses	(3.2)
12 Months or More, Fair Value	34.4
12 Months or More, Unrealized Losses	(4.9)
Total, Fair Value	59.8
Total, Unrealized Losses	(8.1)
Noncurrent [Member] | Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0.5
Less than 12 Months, Unrealized Losses	(0.1)
12 Months or More, Fair Value	0.7
12 Months or More, Unrealized Losses	(0.1)
Total, Fair Value	1.2
Total, Unrealized Losses	(0.2)
Noncurrent [Member] | Obligations of states and other political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	17.4
Less than 12 Months, Unrealized Losses	(2.2)
12 Months or More, Fair Value	29.6
12 Months or More, Unrealized Losses	(4.1)
Total, Fair Value	47.0
Total, Unrealized Losses	(6.3)
Noncurrent [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	7.5
Less than 12 Months, Unrealized Losses	(0.9)
12 Months or More, Fair Value	4.1
12 Months or More, Unrealized Losses	(0.7)
Total, Fair Value	11.6
Total, Unrealized Losses	$ (1.6)