Share-Based Compensation (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share Based Compensation (Textual) [Abstract]
Share-based compensation expense	$ 3.0	$ 2.4	$ 6.1	$ 4.9
Tax benefits	$ 1.2	$ 0.9	$ 2.3	$ 1.8
Vesting period for the 2012 SAR grant			3 years
Portion of an award vesting for the 2012 SAR grant			1/3 vesting after each year
Stock Appreciation Rights (SARs) [Member]
Additional Share Based Compensation (Textual) [Abstract]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, Grants in period			350,200
Restricted Stock [Member]
Additional Share Based Compensation (Textual) [Abstract]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, Grants in period			63,380
Performance Shares [Member]
Additional Share Based Compensation (Textual) [Abstract]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, Grants in period			76,780
Phantom Stock Units [Member]
Additional Share Based Compensation (Textual) [Abstract]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, Grants in period			10,428