Stock-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense for nonvested stock awards	$ 9.5	$ 6.7	$ 16.8	$ 13.7
Minimum [Member] | Performance-Based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, actual expected payout, shares			0
Minimum [Member] | Market-Based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, actual expected payout, shares			0
Maximum [Member] | Performance-Based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, actual expected payout, shares			259
Maximum [Member] | Market-Based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, actual expected payout, shares			129