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Stock Option and Incentive Plan Stock Option and Incentive Plan (Narrative) (Details) $ in Millions | Feb. 09, 2019 USD ($) shares | Feb. 05, 2019 USD ($) yr shares
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2019 MYLTIP [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
TSR Measurement, Years | yr |  | 3
Distributions Percent Before Measurement Date |  | 10.00%
Value of MYLTIP Awards | $ |  | $ 13.5
MYLTIP Value Amortized Into Earnings, Years | yr |  | 4
2016 MYLTIP [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Value of MYLTIP Awards | $ | $ 13.6 |
Final awards percentage of target | 69.50% |
2016 MYLTIP Units Forfeited | 364,980 |
Nareit Office Index adjusted [Member] | 2019 MYLTIP [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Minimum earned awards |  | 0
Maximum Earned Awards |  | 220,734
Target Tier |  | 110,367

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