Revenue - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Utility Revenue [Line Items]
Practical expedient cost incurred to obtain a contract description of amortization term	one year or less
Accounts receivable related to contracts with customers	$ 1,076
Minimum [Member]
Utility Revenue [Line Items]
Capitalized contract cost amortization term	3 years
Maximum [Member]
Utility Revenue [Line Items]
Capitalized contract cost amortization term	20 years
Networks Segment [Member]
Utility Revenue [Line Items]
Customer payment description	one year or less

Capitalized contract cost amortization term.

No definition available.

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- Definition

Practical expedient cost incurred to obtain a contract description of amortization term.

+ References

No definition available.

+ Details

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- Definition

Utility revenue.

+ References

No definition available.

+ Details

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- Definition

Amount to be collected within one year of the balance sheet date (or one operating cycle, if longer) from customers in accordance with the contractual provisions of long-term contracts or programs including amounts billed and unbilled as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(c))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Description of payment terms in contract with customer. Includes, but is not limited to, timing of payment, existence of financing component, variability of consideration and constraint on variable consideration.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130554-203045

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