Goodwill and Intangible Assets - Changes in the Carrying Amount of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Goodwill [Line Items]
Beginning balance	$ 119,130
Goodwill acquired during the period	0
Adjustments to goodwill during the period	0
Ending balance	119,130
Gross goodwill	293,374
Accumulated impairment charges	(174,244)
Radiology
Goodwill [Line Items]
Beginning balance	45,157
Goodwill acquired during the period	0
Adjustments to goodwill during the period	0
Ending balance	45,157
Gross goodwill	199,499
Accumulated impairment charges	(154,342)
Oncology
Goodwill [Line Items]
Beginning balance	42,320
Goodwill acquired during the period	0
Adjustments to goodwill during the period	0
Ending balance	42,320
Gross goodwill	62,222
Accumulated impairment charges	(19,902)
Interventional
Goodwill [Line Items]
Beginning balance	31,653
Goodwill acquired during the period	0
Adjustments to goodwill during the period	0
Ending balance	31,653
Gross goodwill	31,653
Accumulated impairment charges	$ 0