Organization and Summary of Significant Accounting Policies (Cash and Cash Equivalents and Marketable Securities, Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013
Cash and Cash Equivalents [Line Items]
Purchases, Sales, Issuances, Settlements	$ 4,200,000
Loss on sale of auction-rate security	500,000
Cash and cash equivalents	83,709,000	82,646,000
South Korea
Cash and Cash Equivalents [Line Items]
Time deposits	16,900,000	13,300,000
Cash and cash equivalents		26,500,000
Taiwan
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		6,000,000
Japan
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		$ 1,900,000

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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- Definition

Any certificate of deposit or savings account held by a bank or other financial institution for a short-term specified period of time. Because of their short-term, time deposits are considered highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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ATMI INC 10-K