Rent Expense - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) properties healthcareproperty	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) properties healthcareproperty
Operating Leased Assets [Line Items]
Number of properties subject to parking lease	2		2
Number of properties subject to air space lease | healthcareproperty	1		1
Number of properties subject to ground leases	77		77
Number of office space leases	4		4
Maximum lease terms			87 years
Number of properties, held for sale	17		17
Operating Expense | Parking, Air And Ground Leases
Operating Leased Assets [Line Items]
Rent expenses for parking, air, and ground leases | $	$ 0.6	$ 0.6	$ 1.2