Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended								12 Months Ended					12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Phantom Stock [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2008 Restricted Stock [Member]	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member] years		Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2010 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2009 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2012 Chief Executive Officer [Member] Restricted Stock [Member] years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested and Expected to Vest Aggregate Intrinsic Value									$ 17.6	[1]
Compensation expense related to all stock-based compensation plans	8.4	7.8	8.8
Unrecognized compensation costs									2.7					1.1
Weighted-average period of years costs are expected to be recognied over									1.1					3.3
Compensation expense related to award				$ 0.4	$ 1.5	$ 1.3	$ 1.7		$ 2.3		$ 2.3	$ 1.9		$ 0.2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				75,816	556,987	760,728	783,289	665,521	960,388		1,112,868	955,936	570,569	300,000

[1] Incentive shares expected to vest based upon historical forfeitures rate