Commitments and Contingencies (Details) $ in Thousands					1 Months Ended	12 Months Ended
	Nov. 30, 2017 USD ($)	Oct. 18, 2017 USD ($) ft²	May 05, 2017 USD ($)	Jan. 25, 2016 USD ($) a	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($) ft²	Jan. 11, 2018 a	Oct. 04, 2017 USD ($) a
Subsequent events
Purchase and sale obligations
Number of acres | a							14
Agreement to sell
Purchase and sale obligations
Purchase Option Term			3 months
Agreement Term of Extension			3 years	3 years
Agreement Extension Fee	$ 140
Number of acres to be sold | a				280
Sale price			$ 7,800	$ 7,700
Additional option fee			$ 35		$ 120
Purchase agreement
Purchase and sale obligations
Purchase obligations								$ 2,600
Number of acres | a								22
Lease and development agreement
Purchase and sale obligations
Purchase obligations		$ 17,500
Agreement Term of Extension		5 years
Area Of Building | ft²		234,000
Lease term		12 years 6 months
Mortgage loan		$ 13,800
Term of debt		15 years
Interest rate (as a percent)		4.51%
Amortization period of debt		25 years
Lease and development agreement | Expansion option
Purchase and sale obligations
Area Of Building | ft²		54,000
Lease term		10 years
Obligations For Investments In Real Estate Assets
Purchase and sale obligations
Purchase obligations	$ 3,037					$ 3,037
Area Of Building | ft²						134,000