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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Employee Stock Option [Member]	Sep. 30, 2013 Employee Stock Option [Member]	Sep. 30, 2014 Share Awards and Vesting [Member]	Sep. 30, 2013 Share Awards and Vesting [Member]	Sep. 30, 2014 Minimum [Member] Employee Stock Option [Member]	Sep. 30, 2014 Minimum [Member] Share Awards and Vesting [Member]	Sep. 30, 2014 Maximum [Member] Employee Stock Option [Member]	Sep. 30, 2014 Maximum [Member] Share Awards and Vesting [Member]	Jun. 30, 2011 2011 Share Incentive Plan [Member]	Sep. 30, 2014 2011 Share Incentive Plan [Member]
Total fungible units to be issued													9,100,000	5,500,000
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
Full Value award in the fungible unit conversion ratio													1.0
Expiration value of option right or other award													0.83
Common shares which could be granted pursuant to full value awards														1,600,000
Options exercised during the period			360,058		400,000	200,000
Total intrinsic value of options exercised during the period					$ 6.9	$ 5.2
Total unrecognized compensation cost which is expected to be amortized							40.2
Remaining weighted average contractual life (years) outstanding options					4 years 4 months 6 days
Remaining weighted average contractual life (years) exercisable options					4 years 4 months 6 days
Vesting period, years									3 years	3 years	5 years	5 years
Expected amortized period of unrecognized compensation expected to be recognized for share-based compensation plans							4 years
Fair value of shares vested							16.0	14.9
Allocated Share-based Compensation Expense	4.2	3.9	12.1	11.3	0.3
Total capitalized compensation cost for option and share awards	$ 0.7	$ 0.5	$ 2.0	$ 1.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			84,452