Commitments and Contingencies - Construction Activity (Details) ft² in Thousands, $ in Millions	Jun. 30, 2018 USD ($) ft²
Other Commitments [Line Items]
Approximate Square Feet	14,900
Medical Office Building Expansion | NORTH CAROLINA
Other Commitments [Line Items]
Approximate Square Feet	38
Medical Office Building | NORTH CAROLINA
Other Commitments [Line Items]
Total amount funded | $	$ 7.9
Medical Office Building | COLORADO
Other Commitments [Line Items]
Approximate Square Feet	151
Total amount funded | $	$ 15.5