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Stock Option and Incentive Plan (Narrative) (Details) | Feb. 03, 2017 USD ($) shares | Jan. 25, 2017 USD ($) yr tiers | Feb. 04, 2016 USD ($) shares | Feb. 06, 2015 USD ($) shares | May 15, 2012 yr shares | Jan. 01, 2015 USD ($)
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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 2017 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Tiers | tiers |  | 4 |  |  |  |
TSR measurement (in years) | yr |  | 3 |  |  |  |
Distributions percent before measurement date |  | 10.00% |  |  |  |
Indices Used to Compare TSR |  | 2 |  |  |  |
Threshold Tier |  | $ 10,700,000 |  |  |  |
Target Tier |  | 21,300,000 |  |  |  |
High Tier |  | 32,000,000 |  |  |  |
Exceptional Tier |  | $ 42,700,000 |  |  |  |
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 |  | $ 17,700,000 |  |  |  |
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 | $ 3,500,000 |  |  |  |  |
MYLTIP Units forfeited | shares | 447,386 |  |  |  |  |
Final awards percentage of target | 27.70% |  |  |  |  |
Minimum [Member] | MYLTIP 2017 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Potential Awards Earned |  | $ 0 |  |  |  |
Maximum [Member] | MYLTIP 2017 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Potential Awards Earned |  | $ 42,700,000 |  |  |  |
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
Cohen & Steers Realty Majors Portfolio Index [Member] | MYLTIP 2017 [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 2017 [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 2020 [Member] | MYLTIP 2017 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Vesting Percentage |  | 50.00% |  |  |  |
MYLTIP vesting 2021 | MYLTIP 2017 [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Vesting Percentage |  | 50.00% |  |  |  |

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