Stock-based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation arrangement by share-based payment award, restricted stock units, award measurement period			3 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense for nonvested stock units	$ 9.5	$ 13.5	$ 37.3	$ 40.0
Performance-based Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation arrangement by share-based payment award, restricted stock units, expected payout (in shares)			0
Performance-based Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation arrangement by share-based payment award, restricted stock units, expected payout (in shares)			342,000
Market-based Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation arrangement by share-based payment award, restricted stock units, expected payout (in shares)			0
Market-based Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation arrangement by share-based payment award, restricted stock units, expected payout (in shares)			172,000