Indebtedness (Credit Facilities) (Details) - USD ($)	Sep. 30, 2020	Feb. 10, 2020	Jan. 31, 2020
Line of Credit Facility [Line Items]
Committed credit facilities	$ 7,500,000,000
364-day revolving credit expiring February 2, 2021 [Member]
Line of Credit Facility [Line Items]
Committed credit facilities	2,000,000,000.0		$ 2,000,000,000.0
Multi-year revolving credit, expiring October 1, 2022 [Member]
Line of Credit Facility [Line Items]
Committed credit facilities	3,500,000,000
Multi-year Revolving Credit Facility, Expiring February 10, 2025 [Member]
Line of Credit Facility [Line Items]
Committed credit facilities	$ 2,000,000,000.0	$ 2,000,000,000.0