Segment Information - Summary of Identifiable Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Summary of Company's identifiable assets by segment
Identifiable assets	$ 645,642	$ 659,864
Operating Segments | Radiology
Summary of Company's identifiable assets by segment
Identifiable assets	290,480	301,137
Operating Segments | Oncology
Summary of Company's identifiable assets by segment
Identifiable assets	251,382	256,456
Operating Segments | Interventional
Summary of Company's identifiable assets by segment
Identifiable assets	81,288	82,221
Corporate / Other
Summary of Company's identifiable assets by segment
Identifiable assets	$ 22,492	$ 20,050