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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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

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Contractual interest rate for funds borrowed, under the debt agreement.

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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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The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

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Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

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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.

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The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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Long-Term Debt - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019
Debt Disclosure [Abstract]
Interest paid, net of amounts capitalized			$ 247	$ 204
Debt Instrument [Line Items]
Maximum borrowing capacity under credit facility					$ 4,500
Senior Notes \| Series BB Notes
Debt Instrument [Line Items]
Senior notes, face amount		$ 300	300
Senior Notes \| Series CC Notes
Debt Instrument [Line Items]
Senior notes, face amount		$ 550	$ 550
Interest rate		3.60%	3.60%
Senior Notes \| Series BB and Series CC Notes
Debt Instrument [Line Items]
Proceeds from debt offering		$ 841
LIBOR \| Senior Notes \| Series BB Notes
Debt Instrument [Line Items]
Variable interest rate		0.65%
Subsequent Event \| Senior Notes \| Series DD Notes
Debt Instrument [Line Items]
Senior notes, face amount	$ 550
Proceeds from debt offering	$ 545
Interest rate	2.125%
Interest Rate Swap \| LIBOR \| Senior Notes \| Series CC Notes
Debt Instrument [Line Items]
Variable interest rate from interest rate swap		1.1205%
Interest Rate Swap \| Subsequent Event \| LIBOR \| Senior Notes \| Series DD Notes
Debt Instrument [Line Items]
Variable interest rate from interest rate swap	0.754%