Related Party Transactions - Schedule of Related Parties (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Natural gas sales to/(from) affiliates	$ (111)	$ (38)	$ (4)
Services received from affiliates	65	65	67
Affiliate [Member]
Related Party Transaction [Line Items]
Accounts receivable excluding asset management agreements	10	1
Accounts payable	16	20
Taxes receivable	0	1
Taxes payable	4	4
Emera Energy Services Inc [Member]
Related Party Transaction [Line Items]
Accounts receivable related to asset management agreements to Emera Energy Services Inc.	4	2
TECO Energy [Member]
Related Party Transaction [Line Items]
Dividends to TECO Energy	373	362	292
Equity contributions from TECO Energy	$ 395	$ 345	$ 190

Accounts receivable excluding asset management agreements.

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Accounts receivable related to asset management agreements.

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Natural gas sales to (from) affiliates.

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Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.

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Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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The cash inflow from parent as a source of financing that is recorded as additional paid in capital.

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Amount of transactions with related party during the financial reporting period.

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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.

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Carrying value as of the balance sheet date of obligations incurred and payable for statutory income, sales, use, payroll, excise, real, property and other taxes.

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