Debt and Credit Facilities - Additional Information (Details) - USD ($)	1 Months Ended
	Jun. 30, 2019	Nov. 30, 2018	Sep. 30, 2019
364 Day Credit Agreement Expiring 2020 [Member]
Line Of Credit Facility [Line Items]
Initiation date		Nov. 30, 2018
Maximum borrowing capacity		$ 5,000,000,000
Three Year Agreement Expiring 2022 [Member]
Line Of Credit Facility [Line Items]
Initiation date		Nov. 30, 2018
Maximum borrowing capacity		$ 5,000,000,000
Five Year Agreement Expiring 2024 [Member]
Line Of Credit Facility [Line Items]
Initiation date		Nov. 30, 2018
Maximum borrowing capacity		$ 5,000,000,000
Total Committed Bank Credit Facilities [Member]
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			$ 5,500,000,000
Committed Bank Credit Facility Expiring 2020 [Member]
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			2,300,000,000
Committed Bank Credit Facility Expiring 2021 [Member]
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			650,000,000
Committed Bank Credit Facility Expiring 2022 [Member]
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			2,100,000,000
Committed Bank Credit Facility Expiring 2023 [Member]
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			475,000,000
Three Year Revolving Credit Facility Expiring 2022 [Member]
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			5,000,000,000
Credit facilities amount outstanding			$ 0
Secured notes and loans payable [Member]
Line Of Credit Facility [Line Items]
New revolving asset backed securities period	5 years
Secured notes and loans payable [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Percentage of initial principal amount	50.00%