Defined Contribution Plan (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Discretionary matching contributions	$ 1.5	$ 1.6	$ 1.6
Greater Than Zero And Less Than Three Percent Of Employee Salary [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of matching contribution percentage matched	100.00%
Matching contributions, as a percentage of the employee's eligible compensation	3.00%
Greater Than Three And Less Than Five Percent Of Employee Salary [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of matching contribution percentage matched	50.00%
Matching contributions, as a percentage of the employee's eligible compensation	2.00%
Greater Than Five Percent Of Employee Salary [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of matching contribution percentage matched	0.00%
Matching contributions, as a percentage of the employee's eligible compensation	5.00%

ATMI INC 10-K