Variable Interest Entities (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity, Not Primary Beneficiary [Member] \| Other Receivables Investments in Unconsolidated Entities and Other Assets [Member]
Variable Interest Entity [Line Items]
Aggregate investment balance	$ 97	$ 92
Investments Qualifying for Federal Tax Credits [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Aggregate investment balance	321	189
Investment In Low Income Housing Properties [Member] \| Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Equity method investments debt balance	278	151
Trust For Final Capping, Closure, Post-closure Or Environmental Remediation Obligations [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Long-term other assets [Member]
Variable Interest Entity [Line Items]
Value of consolidated VIEs	$ 108	$ 103

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

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