Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income (loss)	$ 59,246	$ 29,924	$ 34,871
Other comprehensive income (loss)-
Pension adjustment	(13,502)	(401)	5,736
Tax benefit (expense)	4,985	160	(2,226)
Unrealized gain (loss) on interest rate swap agreement	(2,373)	(3,584)	2,915
Tax benefit (expense)	889	1,320	(1,136)
Unrealized gain (loss) on available-for-sale securities	(10,366)	(11,395)	24,265
Tax benefit (expense)	1,022	4,119	(5,141)
Foreign currency translation adjustment	(25,322)	7,203	12,876
Total other comprehensive income (loss)	(44,667)	(2,578)	37,289
Comprehensive income (loss)	14,579	27,346	72,160
AMCOL Shareholders [Member]
Net income (loss)	59,111	30,347	34,799
Other comprehensive income (loss)-
Pension adjustment	(13,502)	(401)	5,736
Tax benefit (expense)	4,985	160	(2,226)
Unrealized gain (loss) on interest rate swap agreement	(2,373)	(3,584)	2,915
Tax benefit (expense)	889	1,320	(1,136)
Unrealized gain (loss) on available-for-sale securities	(10,366)	(11,395)	24,265
Tax benefit (expense)	1,022	4,119	(5,141)
Foreign currency translation adjustment	(24,559)	6,543	12,482
Total other comprehensive income (loss)	(43,904)	(3,238)	36,895
Comprehensive income (loss)	15,207	27,109	71,694
Noncontrolling Interest [Member]
Net income (loss)	135	(423)	72
Other comprehensive income (loss)-
Pension adjustment
Tax benefit (expense)
Unrealized gain (loss) on interest rate swap agreement
Tax benefit (expense)
Unrealized gain (loss) on available-for-sale securities
Tax benefit (expense)
Foreign currency translation adjustment	(763)	660	394
Total other comprehensive income (loss)	(763)	660	394
Comprehensive income (loss)	$ (628)	$ 237	$ 466