Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule Of Share Based Compensation Stock Options Activity [Table Text Block]

					Weighted-
			Weighted-		Average
			Average		Remaining	Aggregate
			Exercise		Contractual	Intrinsic
		Shares	Price		Term	Value
Outstanding at January 1, 2014		3,248,699	$	67.51
Granted		49,088		91.32
Exercised		(434,204)		67.27
Cancelled or expired		(43,468)		104.74
Outstanding at December 31, 2014		2,820,115	$	67.38	4.6	$	145,317,000
Options vested and expected to vest at
	December 31, 2014	2,818,587	$	67.37	4.6	$	145,271,000
Options exercisable at December 31, 2014		2,606,260	$	65.62	4.4	$	138,912,000

Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Table Text Block]

	December 31,
	2014	2013	2012
Expected volatility	36.00%	36.00%	36.00%
Expected life	5.0 years	5.0 years	5.0 years
Risk free interest rate	1.81%	0.91%	1.05%
Expected dividend yield	4.10%	4.30%	4.30%

Schedule Of Sharebased Compensation Restricted Stock And Restricted Stock Units Activity [Table Text Block]

			Weighted-Average
			Grant-Date
Unvested Shares		Shares	Fair Value
	Unvested at January 1, 2014	29,664	$	79.24
	Granted	11,475		91.31
	Vested	(15,733)		74.61
	Cancelled or expired	(2,957)		87.42
	Unvested at December 31, 2014	22,449		87.58

Schedule Of Sharebased Compensation Restricted Operating Partnership Units Activity [Table Text Block]

			Weighted-Average
			Grant-Date
Unvested Units		Units	Fair Value
	Unvested at January 1, 2014	765,971	$	76.27
	Granted	226,638		86.79
	Vested	(327,555)		69.48
	Cancelled or expired	(6,575)		83.16
	Unvested at December 31, 2014	658,479		83.20