Commitments and Contingencies - Construction Activity (Details) $ in Millions	Mar. 31, 2018 USD ($) ft²
Other Commitments [Line Items]
Approximate Square Feet	14,500,000
Medical Office Building Expansion | NORTH CAROLINA
Other Commitments [Line Items]
Approximate Square Feet	38,000
Medical Office Building | NORTH CAROLINA
Other Commitments [Line Items]
Total amount funded | $	$ 5.0
Medical Office Building | COLORADO
Other Commitments [Line Items]
Approximate Square Feet	151,000
Total amount funded | $	$ 10.3