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Stock Option and Incentive Plan (Narrative) (Details) |  |  |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Feb. 06, 2015 USD ($) shares | Jan. 21, 2015 USD ($) yr tiers indices | May. 15, 2012 yr shares | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2015 shares | Apr. 02, 2013 shares | Mar. 11, 2013 USD ($)
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 2015 [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 |  |  |  |  |  |
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% |  |  |  |  |  |
MYLTIP units issued | shares |  |  |  |  |  | 375,000 |  |
Value of MYLTIP Awards |  | $ 15,700,000 |  |  |  |  |  |
MYLTIP Value Amortized Into Earnings, Years | yr |  | 4 |  |  |  |  |  |
Minimum [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Potential Awards Earned |  | $ 0 |  |  |  |  |  |
Maximum [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Potential Awards Earned |  | 40,800,000 |  |  |  |  |  |
Threshold [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Amount of Each Tier |  | 8,200,000 |  |  |  |  |  |
Target [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Amount of Each Tier |  | 16,300,000 |  |  |  |  |  |
High [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Amount of Each Tier |  | $ 40,800,000 |  |  |  |  |  |
Chief Executive Officer [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
LTIP units issued (in shares) | shares |  |  |  |  |  |  | 24,231 |
MYLTIP units issued | shares |  |  |  |  |  |  | 38,926 |
Non-qualified stock options issued (in shares) | shares |  |  |  |  |  |  | 50,847 |
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 | $ 13,800,000 |  |  |
Acceleration of Stock Based Compensation in Association with Transition Agreement |  |  |  |  | $ 12,900,000 |  |  |
Cohen & Steers Realty Majors Portfolio Index [Member] | MYLTIP 2015 [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 2015 [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 2018 [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Vesting Percentage |  | 50.00% |  |  |  |  |  |
MYLTIP vesting 2019 [Member] | MYLTIP 2015 [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Vesting Percentage |  | 50.00% |  |  |  |  |  |

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