Summary of Significant Accounting Policies - Roll Forward of Goodwill Activity by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Acquisition measurement period adjustments		$ 116
Impairment		(13,981)
Accumulated Goodwill		55,007		$ 47,937
Accumulated impairment		(40,809)		(26,828)
Goodwill Balance		14,198	$ 27,263	21,109
DermEbx and Radion [Member]
Goodwill [Line Items]
Acquisition cost			6,154
VuComp M-Vu Breast Density Assets [Member]
Goodwill [Line Items]
Acquisition cost		800
Goodwill Balance		800
Detection [Member]
Goodwill [Line Items]
Accumulated Goodwill		800
Fair value allocation		7,663		7,663
Goodwill Balance		8,463	7,663	7,663
Detection [Member] | VuComp M-Vu Breast Density Assets [Member]
Goodwill [Line Items]
Acquisition cost		800
Therapy [Member]
Goodwill [Line Items]
Acquisition measurement period adjustments		116
Impairment	$ (14,000)	(13,981)
Accumulated Goodwill		6,270
Fair value allocation		13,446		13,446
Accumulated impairment		(13,981)
Goodwill Balance		$ 5,735	19,600	$ 13,446
Therapy [Member] | DermEbx and Radion [Member]
Goodwill [Line Items]
Acquisition cost			$ 6,154