Stock-Based Compensation - Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				12 Months Ended			6 Months Ended	12 Months Ended			3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2012 plan	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Maximum	Dec. 31, 2010 Maximum	Dec. 31, 2012 Maximum	Jun. 30, 2012 Stock Options	Dec. 31, 2012 Stock Options	Dec. 31, 2011 Stock Options	Dec. 31, 2010 Stock Options	Mar. 31, 2010 Stock Options Chief Executive Officer	Jun. 30, 2012 Restricted Stock	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2012 Performance-based Options	Dec. 31, 2010 Performance-based Options	Dec. 31, 2012 Performance-based Restricted Shares	Dec. 31, 2010 Performance-based Restricted Shares	Dec. 31, 2012 Stock Incentive Plan 2011	Dec. 31, 2012 Stock Incentive Plan 2011 Stock Options	Dec. 31, 2012 Stock Incentive Plan 2011 All awards other than options and stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 7.3	$ 7.5	$ 6.9						$ 3.6	$ 4.1	$ 3.8	$ 0.8		$ 3.6	$ 3.4	$ 3.1
Number of stock-based compensation award plans	5
Options expiration term	10 years																					10 years
Award annual vesting percentage																	25.00%		25.00%
Number of shares authorized to award																					4,500,000		1,100,000
Number of shares available for grant																					2,098,474
Granted in period, shares	1,178,780	1,401,163	889,089															105,397		265,837
Award vesting period	4 years																4 years		4 years		3 years
Stock-based compensation awards consisting of stock options and restricted stock outstanding, number	4,607,157																				2,237,119
Aggregate Intrinsic Value	0	0	0.7	0.1			0.1
Intrinsic value of options exercised in period					0.1	0.1
Grants in period, weighted average grant date fair value (dollars per share)	$ 2.53	$ 4.15	$ 4.46
Tax benefit from stock-based compensation expense									1.1	1.3	1.2			1.4	1.3	1.2
Total unrecognized compensation expense related to non-vested stock									5.4					4.8
Total compensation cost not yet recognized, period for recognition								1 year 9 months 18 days					1 year 8 months 12 days
Total fair value of shares vested in period														$ 3.3	$ 3.3	$ 3.2