Share-Based Compensation (Summary of Stock Option Activity) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at December 31, 2010, shares	1,553,400
Outstanding at December 31, 2010, weighted average exercise price	$ 32.92
Granted, shares	353,000
Granted, weighted average exercise price	$ 32.50
Exercised, shares	(14,000)
Exercised, weighted average exercise price	$ 7.53
Forfeited or Expired, shares	(77,600)
Forfeited or Expired, weighted average exercise price	$ 34.06
Outstanding at December 31, 2011, shares	1,814,800	1,553,400
Outstanding at December 31, 2011, weighted average exercise price	$ 32.99	$ 32.92
Exercisable at December 31, 2011, shares	1,260,100
Exercisable at December 31, 2011, weighted average exercise price	$ 32.80
Exercisable at December 31, 2011, weighted average remaining contractual term, years	4 years 8 months 12 days
Exercisable at December 31, 2011, average intrinsic value	$ 8.9
Outstanding, weighted average remaining contactual term, years	5 years 10 months 24 days	6 years 9 months 24 days
Outstanding at December 31, 2010, aggrefate intrinsic value	4.7
Outstanding at December 31, 2011, aggrefate intrinsic value	9.5	4.7
Options expected to vest in the next twelve months, shares	286,600
Options expected to vest in the next twelve months, weighted average exercise price	$ 31.96
Options expected to vest in the next twelve months, weighted average remaining contractual term, years	8 years 1 month 6 days
Options expected to vest in the next twelve months, agregate intrinsic value	$ 0.6