Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 891	$ 1,040
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000us-gaap_CommonStockSharesAuthorized	150,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	27,017,824us-gaap_CommonStockSharesIssued	27,017,824us-gaap_CommonStockSharesIssued
Treasury stock, shares	8,486,172us-gaap_TreasuryStockShares	8,488,404us-gaap_TreasuryStockShares
Stock trusts, shares	3,363,351ctg_StockTrustsShares	3,363,351ctg_StockTrustsShares

Stock trusts, shares.

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- Definition

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

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-Topic 210

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-Section S99

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-Subparagraph (SX 210.5-02.4)

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- Definition

Face amount or stated value per share of common stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

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-Name Regulation S-X (SX)

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- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

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- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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- Definition

Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

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-Name Regulation S-X (SX)

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