Debt - Narrative (Details)			1 Months Ended		3 Months Ended
	Aug. 24, 2020 USD ($)	Aug. 06, 2020 USD ($)	Aug. 24, 2020 USD ($)	Jul. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020	May 31, 2020 USD ($)
Special Purpose Entity (SPE)
Secured Borrowings and Collateral [Abstract]
Proceeds from bank debt				$ 340,000,000
Effective interest rate				1.73%
Special Purpose Entity (SPE)
Secured Borrowings and Collateral [Abstract]
Financing receivables sold				$ 355,000,000
Net book value of rights to payments under operating leases sold				10,000,000
Credit Agreement, Amendment No. 3
Credit Agreement [Abstract]
Minimum unrestricted cash				$ 1,000,000,000.0
Maximum ratio of net debt for borrowed money to consolidated EBITDA				4.25
Cash netting cap				$ 1,750,000,000
Credit Agreement
Credit Agreement [Abstract]
Maximum ratio of net debt for borrowed money to consolidated EBITDA						4.25
Senior Notes | 2025 Senior Notes
Senior Notes [Abstract]
Debt value	$ 200,000,000	$ 550,000,000	$ 200,000,000
Debt interest rate, percent		5.00%
Issuance price	100.75%		100.75%
Secured Borrowings and Collateral [Abstract]
Debt interest rate, percent		5.00%
Senior Notes | 2028 Senior Notes
Senior Notes [Abstract]
Debt value	$ 200,000,000	$ 550,000,000	$ 200,000,000
Debt interest rate, percent		5.50%
Issuance price	102.50%		102.50%
Secured Borrowings and Collateral [Abstract]
Debt interest rate, percent		5.50%
Senior Notes | 2025 And 2028 Senior Notes
Senior Notes [Abstract]
Proceeds, net of fees and expenses	$ 405,000,000	$ 1,089,000,000	$ 1,494,000,000
Payments of debt issuance costs					$ 13,000,000
Deferred debt issuance costs					$ 13,000,000
Senior Notes | 2020 Senior Notes 3.500%
Senior Notes [Abstract]
Debt interest rate, percent					3.50%
Debt repurchased					$ 362,000,000
Secured Borrowings and Collateral [Abstract]
Debt repurchased					$ 362,000,000
Debt interest rate, percent					3.50%
Senior Notes | 2020 Senior Notes 2.750%
Senior Notes [Abstract]
Debt interest rate, percent					2.75%
Debt repurchased					$ 376,000,000
Secured Borrowings and Collateral [Abstract]
Debt repurchased					$ 376,000,000
Debt interest rate, percent					2.75%
Senior Notes | 2021 Senior Notes
Senior Notes [Abstract]
Debt value					$ 1,062,000,000
Debt interest rate, percent					4.50%
Secured Borrowings and Collateral [Abstract]
Debt interest rate, percent					4.50%
Senior Notes | 2020 Senior Notes 2.80%
Senior Notes [Abstract]
Debt interest rate, percent							2.80%
Debt repurchased							$ 313,000,000
Secured Borrowings and Collateral [Abstract]
Debt repurchased							$ 313,000,000
Debt interest rate, percent							2.80%