Gain on Sales of Real Estate (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($) item	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($) item
Sales of investment properties
Sales proceeds				$ 6,918,000
Income from discontinued operations		$ 20,000		$ 3,097,000
New properties and properties under development
Sales of investment properties
Number of properties sold | item	5	6	14	17
Sales proceeds	$ 8,200,000	$ 7,000,000	$ 30,500,000	$ 19,700,000
Gain on sales of investment properties	$ 3,700,000	$ 2,000,000	$ 10,900,000	5,800,000
Income from discontinued operations				$ 2,600,000
New properties and properties under development | Crest Net Lease, Inc. (Crest)
Sales of investment properties
Number of properties sold | item				1
Sales proceeds				$ 820,000