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Common Stock (Details) (USD $) | 3 Months Ended | 42 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 26, 2011 | Dec. 05, 2013 | Oct. 23, 2014
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |
Common stock, outstanding | 62,681,887 us-gaap_CommonStockSharesOutstanding |  | 62,681,887 us-gaap_CommonStockSharesOutstanding | 62,981,229 us-gaap_CommonStockSharesOutstanding |  |  |
Common stock, issued | 178,928 us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross | 379,616 us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross |  |  |  |  |
Number of shares repurchased | 500,000 us-gaap_StockRepurchasedDuringPeriodShares |  | 8,000,000 us-gaap_StockRepurchasedDuringPeriodShares |  |  |  |
Stock repurchased (in US dollars) | $ 21,148,000 us-gaap_StockRepurchasedDuringPeriodValue | $ 0 us-gaap_StockRepurchasedDuringPeriodValue | $ 304,700,000 us-gaap_StockRepurchasedDuringPeriodValue |  |  |  |
RepurchaseProgramSep262011 |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |
Stock repurchase, authorized amount (in US dollars) |  |  |  |  | 100,000,000 us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_ShareRepurchaseProgramAxis = eme_RepurchaseProgramSep262011Member |  |
RepurchaseProgramDec052013 |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |
Stock repurchase, authorized amount (in US dollars) |  |  |  |  |  | 100,000,000 us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_ShareRepurchaseProgramAxis = eme_RepurchaseProgramDec052013Member |
Remaining authorized repurchase amount (in US dollars) | 145,300,000 us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 / us-gaap_ShareRepurchaseProgramAxis = eme_RepurchaseProgramDec052013Member |  | 145,300,000 us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 / us-gaap_ShareRepurchaseProgramAxis = eme_RepurchaseProgramDec052013Member |  |  |  |
RepurchaseProgramOct232014 |  |  |  |  |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |  |  |  |  |
Stock repurchase, authorized amount (in US dollars) |  |  |  |  |  |  | $ 250,000,000 us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_ShareRepurchaseProgramAxis = eme_RepurchaseProgramOct232014MemberMember

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- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 + Details
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- Definition Gross number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP). Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans. + References No definition available. + Details
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- Definition Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 + Details
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- Definition Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 + Details
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- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
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- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
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