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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

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 borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

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Balance Type:	credit
Period Type:	instant

- 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.

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Related Party Debt - Schedule of Consolidated Related Party Debt Obligations (Details) - USD ($)	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2017	Aug. 06, 2014
Line Of Credit Facility [Line Items]
Outstanding Balance	$ 2,090,700,000		$ 1,844,000,000.0
Total Capacity	2,990,000,000.0		2,390,000,000.0
Available Capacity	896,000,000.0		543,100,000
Unamortized debt issuance costs	(3,300,000)		(2,900,000)
Line of Credit \| Seven Year Fixed Facility
Line Of Credit Facility [Line Items]
Outstanding Balance	600,000,000.0		0
Total Capacity	600,000,000.0	$ 600,000,000.0	0
Available Capacity	0		0
Line of Credit \| Five Year Revolver Due July 2023
Line Of Credit Facility [Line Items]
Outstanding Balance	494,000,000.0		246,900,000
Total Capacity	760,000,000.0		760,000,000.0
Available Capacity	266,000,000.0		513,100,000
Line of Credit \| Five Year Revolver due December 2022
Line Of Credit Facility [Line Items]
Outstanding Balance	400,000,000.0		1,000,000,000.0
Total Capacity	1,000,000,000.0		1,000,000,000.0
Available Capacity	600,000,000.0		0
Line of Credit \| Five Year Fixed Facility
Line Of Credit Facility [Line Items]
Outstanding Balance	600,000,000.0		600,000,000.0
Total Capacity	600,000,000.0		600,000,000.0
Available Capacity	0		0
Line of Credit \| Zydeco Revolver
Line Of Credit Facility [Line Items]
Outstanding Balance	0		0
Total Capacity	30,000,000.0		30,000,000.0	$ 30,000,000.0
Available Capacity	$ 30,000,000.0		$ 30,000,000.0