Share-Based Compensation and Non-Qualified Deferred Compensation Plan (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended												3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Options [Member]	Sep. 30, 2012 Options [Member]	Sep. 30, 2013 Share Awards and Vesting [Member]	Sep. 30, 2012 Share Awards and Vesting [Member]	Sep. 30, 2013 Minimum [Member] Options [Member]	Sep. 30, 2012 Minimum [Member] Options [Member]	Sep. 30, 2013 Minimum [Member] Share Awards and Vesting [Member]	Sep. 30, 2013 Maximum [Member] Options [Member]	Sep. 30, 2012 Maximum [Member] Options [Member]	Sep. 30, 2013 Maximum [Member] Share Awards and Vesting [Member]	Jun. 30, 2011 2011 Share Incentive Plan [Member]	Sep. 30, 2013 2011 Share Incentive Plan [Member]
Total fungible units to be issued															9,100,000	6,700,000
Units available under the 2011 Share Plan															5,800,000
Fungible units transferred from the 2002 Share Plan to the 2011 Share Plan															3,300,000
Fungible Units To Full Value Award Conversion Ratio															3.45
Expiration value of option right or other award															0.83
Common shares which could be granted pursuant to full value awards																1,900,000
Options exercised during the period			182,664		200,000	500,000
Exercise price range for options exercised during the period									$ 30.06	$ 30.06		$ 62.32	$ 51.37
Total intrinsic value of options exercised during the period					$ 5.2	$ 12.0
Total unrecognized compensation cost related to unvested options which is expected to be amortized					0.1		40.1
Remaining weighted average contractual life (years) outstanding options					3 years 183 days
Remaining weighted average contractual life (years) exercisable options					3 years 37 days
Vesting period, years									3 years		3 years	5 years		5 years
Options granted in current year			0		0
Expected amortized period of unrecognized compensation expected to be recognized for share-based compensation plans							4 years
Fair value of shares vested							14.9	13.4
Total compensation cost for option and share awards	3.9	3.6	11.3	10.4
Total capitalized compensation cost for option and share awards	$ 0.5	$ 0.4	$ 1.6	$ 1.1