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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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Number of common shares reserved for future issuance related to deferred compensation arrangements with individuals.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Unrecognized cost of unvested options awarded to employees as compensation.

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The cash outflow for cost incurred directly with the issuance of an equity security.

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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.

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Aggregate par or stated value of issued nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable preferred shares, par value and other disclosure concepts are in another section within stockholders' equity.

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Shareholders' capital - Additional Information (Detail) CAD / shares in Units, CAD in Thousands			2 Months Ended	6 Months Ended	12 Months Ended
	Nov. 10, 2017 CAD CAD / shares shares	Dec. 29, 2014 CAD CAD / shares shares	Mar. 02, 2018 shares	Jun. 30, 2016 shares	Dec. 31, 2017 CAD Right vote CAD / shares shares	Dec. 31, 2016 CAD CAD / shares shares
Stockholders Equity Note [Line Items]
Number of entitled votes per common share \| vote					1
Number of voting rights per share \| Right					1
Discount rate on share purchases					50.00%
Common shares issued (in shares)					43,470,000	12,938,457
Discount rate on share purchases under dividend reinvestment plan					5.00%
Carrying amount \| CAD					CAD 213,805	CAD 213,805
Preferred stock redemption price per share (in CAD per share) \| CAD / shares					CAD 25
Total share-based compensation expense \| CAD					CAD 10,804	5,675
Death Benefits
Stockholders Equity Note [Line Items]
Stock options exercised period					1 year
Resignation or Termination
Stockholders Equity Note [Line Items]
Stock options exercised period					30 days
Maximum \| Retirement
Stockholders Equity Note [Line Items]
Stock options exercised period					90 days
Minimum
Stockholders Equity Note [Line Items]
Percentage of outstanding stock to be purchased to acquire discount (or more)					20.00%
Subsequent Event
Stockholders Equity Note [Line Items]
Additional shares issued under dividend reinvestment plan (in shares)			1,063,572
Employee Stock Option
Stockholders Equity Note [Line Items]
Total share-based compensation expense \| CAD					CAD 3,990	3,006
Unrecognized compensation costs, non-vested options \| CAD					CAD 2,796
Unrecognized compensation costs, non-vested options, period of recognition					1 year 7 months 10 days
Stock Option Plans \| Maximum
Stockholders Equity Note [Line Items]
Percentage of shares reserves under plan (must not exceed)					8.00%
Performance Share Units
Stockholders Equity Note [Line Items]
Maximum aggregate number of shares reserved for future issuance (in shares)					7,000,000
Performance share units granting period					3 years
Percentage of shares issued on number of PSU grants, minimum					2.00%
Percentage of shares issued on number of PSU grants, maximum					237.00%
Employee share purchase
Stockholders Equity Note [Line Items]
Total share-based compensation expense \| CAD					CAD 568	CAD 238
Vesting period of matching contribution shares					1 year
Maximum aggregate number of shares reserved for future issuance (in shares)					2,000,000
Common stock, shares issued (in shares)					283,523	144,264
Deferred Share Units
Stockholders Equity Note [Line Items]
Maximum aggregate number of shares reserved for future issuance (in shares)					1,000,000
Shares issued during period (in shares)					293,906	224,663.24
Performance share units
Stockholders Equity Note [Line Items]
Total share-based compensation expense \| CAD					CAD 5,475	CAD 1,748
Unrecognized compensation costs, non-vested awards \| CAD					CAD 8,471
Unrecognized compensation costs, non-vested options, period of recognition					1 year 10 months 2 days
Series A Preferred Stock
Stockholders Equity Note [Line Items]
Preferred stock issued (in shares)					4,800,000	4,800,000
Shares issued, price per share (CAD per share) \| CAD / shares					CAD 25	CAD 25
Carrying amount \| CAD					CAD 116,546	CAD 116,546
Fixed cumulative annual dividend per share (CAD per share) \| CAD / shares					CAD 1.125
Subsequent yield period					5 years
Preferred stock, Subsequent redemption period					5 years
Series C Preferred Stock
Stockholders Equity Note [Line Items]
Preferred stock redemption price per share (in CAD per share) \| CAD / shares					CAD 53,400
Redeemable preferred stock issued (in shares)					100
Series D Preferred Stock
Stockholders Equity Note [Line Items]
Preferred stock issued (in shares)					4,000,000	4,000,000
Shares issued, price per share (CAD per share) \| CAD / shares					CAD 25	CAD 25
Carrying amount \| CAD					CAD 97,259	CAD 97,259
Fixed cumulative annual dividend per share (CAD per share) \| CAD / shares					CAD 1.25
Subsequent yield period					5 years
Preferred stock, Subsequent redemption period					5 years
Government of Canada Bond Yield \| Series A Preferred Stock
Stockholders Equity Note [Line Items]
Dividend variable interest rate					2.94%
Government of Canada Bond Yield \| Series D Preferred Stock
Stockholders Equity Note [Line Items]
Dividend variable interest rate					3.28%
Government of Canada Treasury Bill Yield \| Series B Preferred Stock
Stockholders Equity Note [Line Items]
Dividend variable interest rate					2.94%
Government of Canada Treasury Bill Yield \| Series E Preferred Stock
Stockholders Equity Note [Line Items]
Dividend variable interest rate					3.28%
Emera \| Subscription receipts \| Park Water Company
Stockholders Equity Note [Line Items]
Common shares issued (in shares)		3,316,583
Issuance of convertible debentures, net of costs \| CAD		CAD 33,000
Additional shares issued under dividend reinvestment plan (in shares)				252,011
Shares issued, price per share (CAD per share) \| CAD / shares		CAD 9.95
Emera \| Odell Wind Facility \| Subscription receipts
Stockholders Equity Note [Line Items]
Common shares issued (in shares)		8,708,170
Issuance of convertible debentures, net of costs \| CAD		CAD 77,503
Additional shares issued under dividend reinvestment plan (in shares)				661,693
Shares issued, price per share (CAD per share) \| CAD / shares		CAD 8.90
Range One \| Employee share purchase
Stockholders Equity Note [Line Items]
Employer matching contribution, percent					20.00%
Range Two \| Employee share purchase
Stockholders Equity Note [Line Items]
Employer matching contribution, percent					10.00%
Range Three \| Employee share purchase
Stockholders Equity Note [Line Items]
Employer matching contribution, percent					15.00%
Public Stock Offering [Member]
Stockholders Equity Note [Line Items]
Sale of stock, price per share (CAD per share) \| CAD / shares	CAD 13.25
Payments of Stock Issuance Costs \| CAD	CAD 24,342
Public Stock Offering [Member] \| Common shares
Stockholders Equity Note [Line Items]
Number of shares issued pursuant to public offering	43,470,000
Cash proceeds from issuance of shares \| CAD	CAD 576,000
Payments Of Stock Issuance Costs, Net of Tax \| CAD	CAD 17,895