Loss Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net loss attributable to Alliance HealthCare Services, Inc.	$ (614)	$ (1,190)
Denominator:
Weighted average shares — basic (shares)	10,973	10,779
Effect of dilutive securities:
Stock options and RSUs	0	0
Weighted average shares — diluted (shares)	10,973	10,779
Net loss per common share attributable to Alliance HealthCare Services, Inc.:
Basic	$ (0.06)	$ (0.11)
Diluted	$ (0.06)	$ (0.11)
Stock options excluded from the computation of diluted per share amounts:
Weighted average shares for which the exercise price exceeds average market price of common stock	323	465
Average exercise price per share that exceeds average market price of common stock (dollars per share)	$ 29.37	$ 25.34