Employee Benefit Plans - Fair Value of Pension Plan Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Hedge Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	$ 4.6	$ 4.0	$ 3.9
Fair Value Measurements Recurring [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	45.1	39.1
Fair Value Measurements Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	21.0	14.1
Fair Value Measurements Recurring [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	19.5	21.0
Fair Value Measurements Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	4.6	4.0
Fair Value Measurements Recurring [Member] \| Short Term Investment Funds [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0.1	0.6
Fair Value Measurements Recurring [Member] \| Short Term Investment Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Short Term Investment Funds [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0.1	0.6
Fair Value Measurements Recurring [Member] \| Short Term Investment Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| US Equity Securities [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	17.3	14.0
Fair Value Measurements Recurring [Member] \| US Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	7.4	1.4
Fair Value Measurements Recurring [Member] \| US Equity Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	9.9	12.6
Fair Value Measurements Recurring [Member] \| US Equity Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| International Equity Securities [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	12.3	9.5
Fair Value Measurements Recurring [Member] \| International Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	4.4	4.5
Fair Value Measurements Recurring [Member] \| International Equity Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	7.9	5.0
Fair Value Measurements Recurring [Member] \| International Equity Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| AMCOL International Common Stock [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	2.4	2.1
Fair Value Measurements Recurring [Member] \| AMCOL International Common Stock [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	2.4	2.1
Fair Value Measurements Recurring [Member] \| AMCOL International Common Stock [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| AMCOL International Common Stock [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Governmental Agencies [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0.8	0.7
Fair Value Measurements Recurring [Member] \| Governmental Agencies [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Governmental Agencies [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0.8	0.7
Fair Value Measurements Recurring [Member] \| Governmental Agencies [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Corporate Bonds [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	6.8	5.4
Fair Value Measurements Recurring [Member] \| Corporate Bonds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	6.8	5.4
Fair Value Measurements Recurring [Member] \| Corporate Bonds [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Corporate Bonds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Guaranteed Investment Contracts [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		1.3
Fair Value Measurements Recurring [Member] \| Guaranteed Investment Contracts [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		0
Fair Value Measurements Recurring [Member] \| Guaranteed Investment Contracts [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		1.3
Fair Value Measurements Recurring [Member] \| Guaranteed Investment Contracts [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		0
Fair Value Measurements Recurring [Member] \| Real Estate Index Funds [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0.8	0.8
Fair Value Measurements Recurring [Member] \| Real Estate Index Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Real Estate Index Funds [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0.8	0.8
Fair Value Measurements Recurring [Member] \| Real Estate Index Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Commodities Linked Funds [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		0.7
Fair Value Measurements Recurring [Member] \| Commodities Linked Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		0.7
Fair Value Measurements Recurring [Member] \| Commodities Linked Funds [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		0
Fair Value Measurements Recurring [Member] \| Commodities Linked Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets		0
Fair Value Measurements Recurring [Member] \| Hedge Funds [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	4.6	4.0
Fair Value Measurements Recurring [Member] \| Hedge Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Hedge Funds [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	0	0
Fair Value Measurements Recurring [Member] \| Hedge Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of pension plan assets [Abstract]
Fair value of pension plan assets	$ 4.6	$ 4.0

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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