Investments in Real Estate and Real Estate Under Construction - Summary of development arrangements outstanding (Details) ft² in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) ft²
Investments in Real Estate and Real Estate Under Construction [Line Items]
Square Feet | ft²	1,030
Expected Maximum Commitment/Contribution	$ 265,609
Joint Venture [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Ownership percentage	100.00%
Lake Jackson, Texas [Member] | Office Building [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Square Feet | ft²	664
Expected Maximum Commitment/Contribution	$ 166,164
Lease Term (Years)	20 years
Charlotte, North Carolina [Member] | Office Building [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Square Feet | ft²	201
Expected Maximum Commitment/Contribution	$ 62,445
Lease Term (Years)	15 years
Charlotte, North Carolina [Member] | Office Building [Member] | LCIF [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Square Feet | ft²	201
Expected Maximum Commitment/Contribution	$ 62,445
Lease Term (Years)	15 years
Investment in real estate under construction	$ 24,166
Opelika, Alabama [Member] | Industrial Property [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Square Feet | ft²	165
Expected Maximum Commitment/Contribution	$ 37,000
Lease Term (Years)	25 years