Concentration	9 Months Ended
Sep. 30, 2018
Risks and Uncertainties [Abstract]
Concentration	Concentration Tenant and Credit Concentration We define annualized rental income as the annualized contractual base rents from our tenants pursuant to our lease agreements as of the measurement date, plus straight line rent adjustments and estimated recurring expense reimbursements to be paid to us, and excluding lease value amortization. The U.S. Government, 13 state governments and three other government tenants combined were responsible for approximately 62.5% and 87.5% of our annualized rental income as of September 30, 2018 and 2017, respectively. The U.S. Government is our largest tenant by annualized rental income and was responsible for approximately 45.6% and 59.8% of our annualized rental income as of September 30, 2018 and 2017, respectively. Geographic Concentration At September 30, 2018, our 105 consolidated properties (164 buildings) were located in 30 states and the District of Columbia. Consolidated properties located in Virginia, the District of Columbia, Maryland, California and Georgia were responsible for 23.7%, 18.1%, 15.3%, 9.4% and 6.1% of our annualized rental income as of September 30, 2018, respectively. Consolidated properties located in the metropolitan Washington, D.C. market area were responsible for approximately 44.1% of our annualized rental income as of September 30, 2018.

Concentration

Tenant and Credit Concentration

We define annualized rental income as the annualized contractual base rents from our tenants pursuant to our lease agreements as of the measurement date, plus straight line rent adjustments and estimated recurring expense reimbursements to be paid to us, and excluding lease value amortization. The U.S. Government, 13 state governments and three other government tenants combined were responsible for approximately 62.5% and 87.5% of our annualized rental income as of September 30, 2018 and 2017, respectively. The U.S. Government is our largest tenant by annualized rental income and was responsible for approximately 45.6% and 59.8% of our annualized rental income as of September 30, 2018 and 2017, respectively.

Geographic Concentration

At September 30, 2018, our 105 consolidated properties (164 buildings) were located in 30 states and the District of Columbia. Consolidated properties located in Virginia, the District of Columbia, Maryland, California and Georgia were responsible for 23.7%, 18.1%, 15.3%, 9.4% and 6.1% of our annualized rental income as of September 30, 2018, respectively. Consolidated properties located in the metropolitan Washington, D.C. market area were responsible for approximately 44.1% of our annualized rental income as of September 30, 2018.