Organization (Details)	Mar. 31, 2015 Property
Debt in default of payment terms | Northern Virginia | Wholly owned subsidiary
Investments in real estate
Number of real estate properties	2
Operating office properties
Investments in real estate
Number of real estate properties	178
Square footage of real estate properties (in square feet)	17,700,000
Office properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties	12
Square footage of real estate properties (in square feet)	1,400,000
Partially operational properties
Investments in real estate
Number of real estate properties	1
Land controlled for future development
Investments in real estate
Square footage of real estate properties (in square feet)	1,402
Developable square feet	17,600,000
Partially operational, wholesale data center
Investments in real estate
The expected stabilization critical load after completion of development (in megawatts)	19.25