Allowance for Losses on Financial Assets Allowance for Losses on Financial Assets (Allowance Disclosure) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Allowance for Losses on Financial Assets [Line Items]
Accounts Receivable, Allowance for Credit Loss	$ (444)	$ (138)	$ (73)
Contract with Customer, Asset, Allowance for Credit Loss	(129)	(81)
Allowance for Credit Loss	(802)	(337)
Financing Receivable, Allowance for Credit Loss	(17)	(5)	$ (8)
Accounts Receivable, Credit Loss Expense (Reversal)	(314)
Contract with Customer, Asset, Credit Loss Expense (Reversal)	(48)
Credit Loss Expense, Reversal	(474)
Financing Receivable, Credit Loss, Expense (Reversal)	(12)
Accounts Receivable, Allowance for Credit Loss, Writeoff	8
Allowance for Credit Loss, Writeoff	8
Allowance for Credit Loss, Recovery	1
Other Current Assets [Member]
Allowance for Losses on Financial Assets [Line Items]
Allowance for Credit Loss	(72)	(38)
Credit Loss Expense, Reversal	(34)
Other Noncurrent Assets [Member]
Allowance for Losses on Financial Assets [Line Items]
Allowance for Credit Loss	(140)	$ (75)
Credit Loss Expense, Reversal	(66)
Other Assets, Net, Allowance for Credit Loss, Recovery	$ 1