Stock Options (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010
Shares reserved for issuance upon granting	4,700,000
Share-based compensation expense	$ 9.4	$ 5.8
Total intrinsic value of options exercised	4.3	5.4
Cash received from stock options exercised	1.4	1.2
Performance-Based Unit [Member]
Minimum units vested (shares)	0
Maximum units vested (shares)	1.5
Employee Stock Option [Member]
Share-based compensation expense	5.8	3.7
Total unrecognized compensation cost	12.4
Recognition period for remaining unrecognized compensation expense, weighted-average period (years)	2.10
Restricted Stock Unit Awards [Member]
Share-based compensation expense	3.6	2.1
Total unrecognized compensation cost	10.1
Recognition period for remaining unrecognized compensation expense, weighted-average period (years)	2.2
Aggregate weighted-average grant-date fair value of units granted	11.0	7.6
Aggregate weighted-average grant-date fair value of units vested	$ 5.2	$ 3.7

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Share Based Compensation Arrangement By Share Based Payment Award Other Than Options Vested In Period Weighted Average Grant Date Fair Value

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Aggregate number of common shares reserved for future issuance.

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Costs and payments related to employee benefits and equity-based compensation, such as pension expense and contributions, other postretirement benefits expense and payments, stock or unit options expense, and amortization of restricted stock or unit.

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Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

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As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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