Stock-Based Compensation (Details 4) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock-Based Compensation
Period of U.S. Treasury rates as a basis for assumed risk-free rates (in years)	10
Unrecognized compensation expense (in dollars)	$ 7.6
Recognition period for unrecognized compensation expense (in years)	1 year 10 months 24 days
Performance shares
Stock-Based Compensation
Unvested, beginning balance, shares	0.4
Unvested, beginning balance	$ 19.00
Granted, shares	0.3
Weighted average fair value of options granted per share (in dollars per share)	$ 17.62
Vested, shares	0
Vested	$ 0.00
Unvested, ending balance, shares	0.7
Unvested, ending balance	$ 18.41
Stock Options
Stock-Based Compensation
Weighted average fair value of options granted per share (in dollars per share)	$ 7.97	$ 9.66	$ 5.19
Unrecognized compensation expense (in dollars)	9.7
Recognition period for unrecognized compensation expense (in years)	2 years 4 months 24 days
Assumptions used to estimate the fair value of each option grant
Expected Life (years)	6 years	6 years	6 years
Risk-free Interest rate	1.10%	2.80%	2.90%
Expected volatility	55.00%	52.00%	50.00%
Expected dividend yield	0.60%	0.70%	1.10%
Restricted Stock
Stock-Based Compensation
Unvested, beginning balance, shares	0.9
Unvested, beginning balance	$ 12.65
Granted, shares	0.2
Weighted average fair value of options granted per share (in dollars per share)	$ 16.22
Vested, shares	(0.2)
Vested	$ 6.30
Unvested, ending balance, shares	0.9
Unvested, ending balance	$ 14.86
Unrecognized compensation expense (in dollars)	$ 3.7
Recognition period for unrecognized compensation expense (in years)	1 year 7 months 6 days