Stock Compensation Plans (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Options Vested or Expected to Vest
Number of Options (in shares)	1,697,248
Weighted-Average Remaining Contractual Life	5 years 1 month 6 days
Weighted-Average Exercise Price (in dollars per share)	$ 24.72
Aggregate Intrinsic Value	$ 10.0
Options Exercisable
Number of Options (in shares)	1,359,681
Weighted-Average Exercise Price (in dollars per share)	$ 25.50
Aggregate Intrinsic Value	7.7
Closing market price for common stock (in dollars per share)	$ 28.47
Aggregate pre-tax intrinsic value of stock options exercised	5.1	2.9	0.9
$7.41 - $21.13 | Stock options
Exercise Price
Exercise price, low end of range (in dollars per share)	$ 7.41
Exercise price, high end of range (in dollars per share)	$ 21.13
Options Vested or Expected to Vest
Number of Options (in shares)	566,151
Weighted-Average Remaining Contractual Life	6 years 9 months 18 days
Weighted-Average Exercise Price (in dollars per share)	$ 13.12
Aggregate Intrinsic Value	8.7
Options Exercisable
Number of Options (in shares)	450,335
Weighted-Average Exercise Price (in dollars per share)	$ 12.15
Aggregate Intrinsic Value	7.3
$22.44 - $29.43 | Stock options
Exercise Price
Exercise price, low end of range (in dollars per share)	$ 22.44
Exercise price, high end of range (in dollars per share)	$ 29.43
Options Vested or Expected to Vest
Number of Options (in shares)	440,366
Weighted-Average Remaining Contractual Life	6 years 8 months 12 days
Weighted-Average Exercise Price (in dollars per share)	$ 25.55
Aggregate Intrinsic Value	1.3
Options Exercisable
Number of Options (in shares)	218,615
Weighted-Average Exercise Price (in dollars per share)	$ 27.06
Aggregate Intrinsic Value	$ 0.4
$30.15 - $34.61 | Stock options
Exercise Price
Exercise price, low end of range (in dollars per share)	$ 30.15
Exercise price, high end of range (in dollars per share)	$ 34.61
Options Vested or Expected to Vest
Number of Options (in shares)	527,121
Weighted-Average Remaining Contractual Life	2 years 1 month 6 days
Weighted-Average Exercise Price (in dollars per share)	$ 32.66
Options Exercisable
Number of Options (in shares)	527,121
Weighted-Average Exercise Price (in dollars per share)	$ 32.66
$35.92 - $42.24 | Stock options
Exercise Price
Exercise price, low end of range (in dollars per share)	$ 35.92
Exercise price, high end of range (in dollars per share)	$ 42.24
Options Vested or Expected to Vest
Number of Options (in shares)	163,610
Weighted-Average Remaining Contractual Life	4 years 3 months 18 days
Weighted-Average Exercise Price (in dollars per share)	$ 37.09
Options Exercisable
Number of Options (in shares)	163,610
Weighted-Average Exercise Price (in dollars per share)	$ 37.09