Segment Information - Summary of Identifiable Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of Company's identifiable assets by segment
Identifiable assets	$ 634,887	$ 500,885	$ 489,847
Radiology
Summary of Company's identifiable assets by segment
Identifiable assets	298,634	229,141	240,317
Oncology
Summary of Company's identifiable assets by segment
Identifiable assets	213,698	182,880	158,216
Corporate / Other
Summary of Company's identifiable assets by segment
Identifiable assets	$ 122,555	$ 88,864	$ 91,314