Share-Based Compensation and Benefit Plans (Narrative) (Details)	3 Months Ended	12 Months Ended
	Jun. 30, 2011 shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | shares		202,993	53,358	375,316
Granted, Options Outstanding | shares		12,854	26,752	84,452
Total compensation cost for option and share awards		$ 21,300,000	$ 18,600,000	$ 16,000,000
Total capitalized compensation cost for option and share awards		$ 3,800,000	$ 3,500,000	2,700,000
Percentage Of Market Value Per Share At Which Shares Purchased Under Employee Share Purchase Plan		85.00%
Employee Share Purchase Plan, Maximum Authorized Amount Per Participant		$ 25,000
Share Awards Held In Employee Trust Shares | shares		1,800,000	1,800,000
Share Awards Held In Non Qualified Deferred Compensation Plan Shares		$ 34,500,000	$ 37,100,000
Cash Required By Plan Participants Upon Withdrawal		$ 22,700,000	$ 23,600,000
Share Awards Held In Non Qualified Deferred Compensation Plan Shares | shares		1,100,000	1,300,000
Trading Securities Held In Non Qualified Deferred Compensation Plan Value		$ 59,500,000	$ 30,800,000
Defined Contribution Plan, Cost Recognized		$ 2,700,000	$ 2,600,000	$ 2,200,000
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | shares		200,000	100,000	400,000
Total intrinsic value of options exercised during the period		$ 8,900,000	$ 2,000,000	$ 7,400,000
Remaining weighted average contractual life (years) outstanding options		2 years
Remaining weighted average contractual life (years) exercisable options		2 years
Allocated Share-based Compensation Expense		$ 100,000	200,000	300,000
Share Awards and Vesting [Member]
Total unrecognized compensation cost related to unvested options which is expected to be amortized		25,700,000
Fair value of shares vested		$ 27,200,000	$ 19,200,000	$ 17,100,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		20.00%
Minimum [Member] | Share Awards and Vesting [Member]
Vesting period, years		3 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		33.33%
Maximum [Member] | Share Awards and Vesting [Member]
Vesting period, years		5 years
2011 Share Incentive Plan [Member]
Total fungible units to be issued | shares	9,100,000	3,600,000
Units available under the 2011 Share Plan | shares	5,800,000
Fungible units transferred from the 2002 Share Plan to the 2011 Share Plan | shares	3,300,000
Fungible Units To Full Value Award Conversion Ratio	3.45
Full Value award in the fungible unit conversion ratio | shares	1.0
Expiration value of option right or other award	0.83
Common shares which could be granted pursuant to full value awards | shares		1,100,000