Real Estate Investments - Assets Held for Sale (Details) $ in Millions			3 Months Ended
	Jun. 27, 2018 USD ($) property	Apr. 26, 2018 USD ($) building property	Mar. 31, 2018 property	Jun. 30, 2018 property	Dec. 31, 2017 property
Business Combinations [Abstract]
Number of properties held for sale			13	1	8
Number of properties reclassified to held for sale			5
Gain on disposition of property | $	$ 5.4	$ 22.3
Number of properties exercising purchase option	5	7
Number of single-tenant net leased buildings | building		5
Number of multi-tenant buildings | building		2