XML 179 R164.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Non-controlling Interest In Subsidiaries (Narrative) (Details) - Grand Bahama Power Company Limited [Member] - Non-voting Cumulative Redeemable Variable Perpetual Preferred Shares [Member] | 12 Months Ended
--- | ---
Dec. 31, 2016 BSD / shares
Noncontrolling Interest [Line Items] |
Preferred Stock, Redemption Price Per Share | BSD 1,000
Preferred Stock Per Cent Per Annum Fixed Cumulative Preferential Dividend | 7.25%
Preferred Stock Per Cent Per Annum Fixed Cumulative Preferential Dividend, Next Three Years | 8.50%
Preferred Stock Per Cent Per Annum Fixed Cumulative Preferential Dividend, Four Fiscal Years Thereafter | 10.00%

X
- Definition Preferred Stock Per Cent Per Annum Fixed Cumulative Preferential Dividend + References No definition available. + Details
Name: | ema_PreferredStockPerCentPerAnnumFixedCumulativePreferentialDividend
Namespace Prefix: | ema_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Preferred Stock Per Cent Per Annum Fixed Cumulative Preferential Dividend, Four Fiscal Years Thereafter + References No definition available. + Details
Name: | ema_PreferredStockPerCentPerAnnumFixedCumulativePreferentialDividendFourFiscalYearsThereafter
Namespace Prefix: | ema_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Preferred Stock Per Cent Per Annum Fixed Cumulative Preferential Dividend, Next Three Years + References No definition available. + Details
Name: | ema_PreferredStockPerCentPerAnnumFixedCumulativePreferentialDividendNextThreeYears
Namespace Prefix: | ema_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_MinorityInterestLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644 + Details
Name: | us-gaap_PreferredStockRedemptionPricePerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=ema_GrandBahamaPowerCompanyLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CumulativePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |