Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2009
Net income	$ 11,548	$ 17,248	$ 9,290	$ 13,963	$ 6,106	$ 18,924	$ 7,279	$ 9,376	$ 52,049	$ 41,685	$ 44,111
Foreign currency translation gain (loss)									(46,647)	42,550	(27,898)
Unrecognized losses and prior service costs (credits), net									(9,371)	13,735	(17,094)
Total comprehensive income (loss)									(3,969)	97,970	(881)
Comprehensive (income) loss attributable to noncontrolling interests									(1,072)	(689)	(221)
Comprehensive income (loss) attributable to A. Schulman, Inc.									(5,041)	97,281	(1,102)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(5,921)				50,007				(5,921)	50,007	(6,278)	38,714
Other Comprehensive Income (Loss), Net of Tax									(55,928)	56,285	(44,992)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	13,383				59,940				13,383	59,940	17,390	45,288
Other Comprehensive Income (Loss), Net of Tax									(46,557)	42,550	(27,898)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(19,304)				(9,933)				(19,304)	(9,933)	(23,668)	(6,574)
Other Comprehensive Income (Loss), Net of Tax									$ (9,371)	$ 13,735	$ (17,094)