Income (Loss) Per Common Share (Tables)

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Computation of basic and diluted loss per share

The following table sets forth the computation of basic and diluted loss per share (amounts in thousands, except per share amounts):

	Year Ended December 31,
	2015		2014		2013
Numerator:
Net income (loss) attributable to Alliance HealthCare Services, Inc.	$	6,742	$	10,618	$	(21,483	)
Denominator:
Weighted-average shares-basic		10,741		10,669		10,634
Effect of dilutive securities:
Employee stock options		108		167		—
Weighted-average shares-diluted		10,849		10,836		10,634
Income (loss) per common share attributable to Alliance HealthCare    Services, Inc.:
Basic	$	0.63	$	1.00	$	(2.02	)
Diluted	$	0.62	$	0.98	$	(2.02	)
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		384		337		176
Average exercise price per share that exceeds average market price of    common stock	$	30.16	$	34.75	$	35.02