Stock Option and Incentive Plan (Narrative) (Details)					12 Months Ended
	Feb. 04, 2016 USD ($) shares	Jan. 25, 2016 USD ($) yr indices tiers	Feb. 06, 2015 USD ($) shares	May 15, 2012 yr shares	Dec. 31, 2014 USD ($)	Mar. 11, 2013 USD ($)
MYLTIP 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards	$ 13,500,000
MYLTIP Units forfeited | shares	205,762
Final awards percentage of target	109.50%
OPP Units 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned			$ 40,000,000
Outperformance awards earned			$ 32,100,000
Potential maximum amount of Outperformance Awards earned (percent)			80.00%
2012 OPP Units forfeited | shares			174,549
2012 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Additional Shares Authorized | shares				13,000,000
Other Than Stock Options Awards Conversion Ratio				2.32
Stock Option Awards Conversion Ratio				1.0
Stock Option and Incentive Plan Term Period | yr				10
MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Tiers | tiers		3
TSR measurement (in years) | yr		3
Distributions percent before measurement date		10.00%
Indices Used to Compare TSR | indices		2
Threshold Tier		$ 9,900,000
Target Tier		19,700,000
High Tier		$ 49,300,000
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%
Value of MYLTIP Awards		$ 17,300,000
MYLTIP Value Amortized Into Earnings, Years | yr		4
Minimum [Member] | MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 0
Maximum [Member] | MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential Awards Earned		$ 49,300,000
Board of Directors Chairman [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash Payment Related to Transition Agreement						$ 6,700,000
Target Equity Award Compensation Associated with Transition Agreement						$ 11,100,000
Compensation Expense associated with Transition Agreement					$ 3,900,000
Cohen & Steers Realty Majors Portfolio Index [Member] | MYLTIP 2016 [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] | MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR		50.00%
MYLTIP vesting 2019 [Member] | MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%
MYLTIP vesting 2020 [Member] | MYLTIP 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage		50.00%