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Stock Option and Incentive Plan (Narrative) (Details) $ in Millions	Feb. 06, 2018 USD ($) yr	Feb. 04, 2018 USD ($) shares	Feb. 03, 2017 USD ($) shares	Feb. 04, 2016 USD ($) shares	May 15, 2012 yr shares
MYLTIP 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards | $				$ 13.5
MYLTIP Units forfeited | shares				205,762
Final awards percentage of target				109.50%
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 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR measurement (in years) | yr	3
Distributions percent before measurement date	10.00%
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 | $	$ 13.3
MYLTIP Value Amortized Into Earnings, Years | yr	4
MYLTIP 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards | $			$ 3.5
MYLTIP Units forfeited | shares			447,386
Final awards percentage of target			27.70%
MYLTIP 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of MYLTIP Awards | $		$ 3.6
MYLTIP Units forfeited | shares		337,847
Final awards percentage of target		22.00%
Cohen & Steers Realty Majors Portfolio Index [Member] | MYLTIP 2018
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 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Percentage of Index Used to Compare to TSR	50.00%
MYLTIP vesting 2021 | MYLTIP 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	50.00%
MYLTIP vesting 2022 | MYLTIP 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	50.00%

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