Share-Based Compensation and Non-Qualified Deferred Compensation Plan (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Options [Member]	Mar. 31, 2013 Options [Member]	Mar. 31, 2014 Share Awards and Vesting [Member]	Mar. 31, 2013 Share Awards and Vesting [Member]	Mar. 31, 2014 Minimum [Member] Options [Member]	Mar. 31, 2014 Minimum [Member] Share Awards and Vesting [Member]	Mar. 31, 2014 Maximum [Member] Options [Member]	Mar. 31, 2014 Maximum [Member] Share Awards and Vesting [Member]	Jun. 30, 2011 2011 Share Incentive Plan [Member]	Mar. 31, 2014 2011 Share Incentive Plan [Member]
Total fungible units to be issued											9,100,000	5,600,000
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	180,168		200,000	100,000
Total intrinsic value of options exercised during the period			$ 3.6	$ 4.1
Total unrecognized compensation cost related to unvested options which is expected to be amortized			0		49.2
Remaining weighted average contractual life (years) outstanding options			3 years 6 months
Remaining weighted average contractual life (years) exercisable options			3 years 6 months
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					5 years
Fair value of shares vested					15.5	14.1
Total capitalized compensation cost for option and share awards	0.6	0.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	84,452
Stock Issued During Period, Value, Stock Options Exercised	$ 3.8	$ 3.4	$ 0.3