Loss Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Net loss attributable to Alliance HealthCare Services, Inc.	$ (12,964)	$ (801)	$ (15,382)	$ (5,623)
Denominator:
Weighted-average shares-basic (shares)	10,629	10,633	10,629	10,648
Effect of dilutive securities:
Employee stock options (shares)	0	0	0	0
Weighted-average shares-diluted (shares)	10,629	10,633	10,629	10,648
Loss per common share attributable to Alliance HealthCare Services, Inc.:
Basic (dollars per share)	$ (1.22)	$ (0.08)	$ (1.45)	$ (0.53)
Diluted (dollars per share)	$ (1.22)	$ (0.08)	$ (1.45)	$ (0.53)
Stock options excluded from the computation of diluted per share amounts:
Weighted-average shares for which exercise price exceeds average market price of common stock (shares)	291	858	310	714
Average exercise price per share that exceeds average market price of common stock (dollars per share)	$ 35.31	$ 27.55	$ 34.55	$ 32.25