Face (par) amount of debt instrument at time of issuance.

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Period Type:	instant

- 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.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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-Publisher FASB
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Balance Type:	na
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

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Balance Type:	na
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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

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Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

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Balance Type:	credit
Period Type:	duration

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

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Debt (2016 Credit Facility - Narrative) (Details) - USD ($)		1 Months Ended	12 Months Ended
	Apr. 26, 2018	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2013
Debt Instrument [Line Items]
Repayments of long-term debt			$ 2,095,000,000	$ 1,139,000,000	$ 1,175,000,000
Loss on early extinguishment of debt	$ 8,000,000		17,000,000	70,000,000	$ 51,000,000
Unamortized debt expense			23,000,000	40,000,000
2016 Credit Facility [Member]
Debt Instrument [Line Items]
Unamortized debt expense			$ 4,000,000
Long-term Debt [Member] \| 2013 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 66,000,000	$ 2,000,000,000
Credit facility, maturity date			Dec. 31, 2018
Long-term Debt [Member] \| 2016 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	743,000,000					743,000,000
Unamortized debt expense	4,000,000
Line of credit, amount borrowed				0
Long-term Debt [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Amount outstanding			$ 112,000,000	$ 323,000,000
Revolving Credit Facility And Term Loan Facility [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity						1,934,000,000
Debt, maturity date			Dec. 31, 2020
2016 Term Loan due December 2020 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument face amount						$ 1,191,000,000
Debt, maturity date				Dec. 31, 2020
Repayments of long-term debt	$ 1,191,000,000	$ 1,191,000,000
Unamortized debt expense				$ 8,000,000