Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details) (MYLTIP 2014 [Member], USD $)	0 Months Ended
	Jan. 27, 2014 indices tiers Y
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TRS Measurement, Years	3
Indices Used to Compare TRS	2
Number of Tiers	4
Percentage of annualized TRS for Reduction of Earned Awards	0.00%
Percentage to Cause Some Awards to be Earned Even if on a Relative Basis it Would Not Result in any Earned Awards	12.00%
Distributions Percent Before Measurement Date	10.00%
Value of MYLTIP Awards	$ 12,700,000
MYLTIP Value Amortized Into Earnings, Years	4
Cohen & Steers Realty Majors Portfolio Index [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TRS	50.00%
NAREIT Office Index adjusted [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TRS	50.00%
Exceptional [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	40,200,000
Target [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	13,400,000
Threshold [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	6,700,000
High [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier	26,800,000
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned	40,200,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned	$ 0
MYLTIP Vesting 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	50.00%
Vesting Date	Feb. 03, 2017
MYLTIP vesting 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	50.00%
Vesting Date	Feb. 03, 2018