Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details)	Feb. 04, 2016 USD ($) shares	Jan. 25, 2016 USD ($) yr indices tiers	Feb. 06, 2015 USD ($) shares
2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Measurement, Years | yr		3
Indices Used to Compare TSR | indices		2
Number of Tiers | tiers		3
Percentage of annualized TSR 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		$ 17,300,000
MYLTIP Value Amortized Into Earnings, Years | yr		4
OPP Units 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned			$ 40,000,000
2012 OPP Units Forfeited | shares			174,549
Outperformance awards earned			$ 32,100,000
Potential maximum amount of Outperformance Awards earned (percent)			80.00%
2013 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards	$ 13,500,000
Final awards percentage of target	109.50%
2013 MYLTIP Units Forfeited | shares	205,762
Cohen & Steers Realty Majors Portfolio Index [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
NAREIT Office Index adjusted [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
Threshold [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier		$ 9,900,000
Target [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier		19,700,000
High [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of Each Tier		49,300,000
Maximum [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		49,300,000
Minimum [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 0
MYLTIP vesting 2019 [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%
MYLTIP vesting 2020 [Member] | 2016 MYLTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%