Commitments and Contingencies - Construction Activity (Details) $ in Millions	Sep. 30, 2017 USD ($) ft²
Other Commitments [Line Items]
Approximate Square Feet | ft²	14,400,000
Medical Office Building Expansion | TENNESSEE
Other Commitments [Line Items]
Approximate Square Feet | ft²	70,000
Total amount funded	$ 12.2
Tenant improvements included in construction funded	3.2
Construction activity, estimated remaining fundings	$ 0.4
Medical Office Building Expansion | NORTH CAROLINA
Other Commitments [Line Items]
Approximate Square Feet | ft²	38,000
Medical Office Building | NORTH CAROLINA
Other Commitments [Line Items]
Total amount funded	$ 0.8
Estimated total investment	$ 12.0
Medical Office Building | COLORADO
Other Commitments [Line Items]
Approximate Square Feet | ft²	99,957
Total amount funded	$ 25.2
Estimated total investment	28.2
Overages reimbursed by tenant	$ 2.6