Equity Investments - Schedule of Equity Investments (Details) (USD $) In Thousands, unless otherwise specified
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12 Months Ended |
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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Jul. 09, 2014
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Jun. 30, 2014
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Jul. 02, 2013
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Mar. 15, 2013
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Equity Investments |
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Equity investments |
$ 0us-gaap_EquityMethodInvestments |
$ 517,991us-gaap_EquityMethodInvestments |
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Equity in earnings of investees |
24,460us-gaap_IncomeLossFromEquityMethodInvestments |
25,754us-gaap_IncomeLossFromEquityMethodInvestments |
11,420us-gaap_IncomeLossFromEquityMethodInvestments |
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SIR |
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Equity Investments |
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Ownership Percentage |
0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
44.20%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
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0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
36.70%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
56.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
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Equity investments |
0us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
512,078us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
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Equity in earnings of investees |
24,516us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
21,153us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
0us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_SelectIncomeREITMember |
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GOV |
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Equity Investments |
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Ownership Percentage |
0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
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18.20%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
Equity investments |
0us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
0us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
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Equity in earnings of investees |
0us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
4,111us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
10,836us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_GovernmentPropertiesIncomeTrustMember |
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AIC |
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Equity Investments |
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Ownership Percentage |
0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
12.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
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Equity investments |
0us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
5,913us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
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Equity in earnings of investees |
$ (56)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
$ 490us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
$ 584us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = eqc_AffiliatesInsuranceCompanyMember |
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