Borrowing and Lines of Credit (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Line of Credit Facility [Line Items]
Maximum Commercial Paper Borrowing Authority		$ 5,000		$ 5,000
Aggregate Line of Credit Agreements, Maximum Borrowing Capacity		7,000		7,000
Debt Exchanged		$ 8,200		$ 8,200
Average Years of Maturity of Long Term Debt				14 years
Average interest expense rate		4.20%	3.60%	4.00%	3.70%
Repayments of Debt				$ 15,174	$ 600
Forecast [Member]
Line of Credit Facility [Line Items]
Repayments of Debt	$ 1,000
5.0B Revolving Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 5,000		$ 5,000
Line of Credit Facility, Initiation Date				Mar. 16, 2020
$2.0B revolving credit agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date				Feb. 11, 2020
Termination of Credit Agreement		2,000		$ 2,000
Borrowings [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		2,100		$ 2,100
$2.20B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date				Apr. 03, 2020
Termination of Credit Agreement		2,200		$ 2,200
4.0B Term Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date				Mar. 03, 2020
Termination of Credit Agreement		4,000		$ 4,000
2.15B Multicurrency Revolving Credit Agreement [Member]
Line of Credit Facility [Line Items]
Termination of Credit Agreement		2,150		2,150
March 20, 2020 $500M Term Loan Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		1,000		$ 1,000
Line of Credit Facility, Expiration Date				May 05, 2020
Line of Credit Facility, Initiation Date				Mar. 20, 2020
Termination of Credit Agreement		500		$ 500
March 23, 2020 $500M term credit agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date				Apr. 28, 2020
Line of Credit Facility, Initiation Date				Mar. 23, 2020
Termination of Credit Agreement		500		$ 500
1.0B Credit Agreement - Otis [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date				Feb. 10, 2020
Termination of Credit Agreement		1,000		$ 1,000
1.75B Credit Agreement - Carrier [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date				Feb. 10, 2020
Termination of Credit Agreement		1,750		$ 1,750
$2.0B May 6, 2020 revolving credit agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 2,000		$ 2,000
Line of Credit Facility, Expiration Date				May 05, 2021
Line of Credit Facility, Initiation Date				May 06, 2020