Allowance for Losses on Financial Assets Allowance for Losses on Financial Assets (Allowance Disclosure) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Allowance for Losses on Financial Assets [Line Items]
Allowance for Credit Loss	$ (740)	$ (337)
Credit Loss Expense, Reversal	(406)
Allowance for Credit Loss, Writeoff	3
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Accounts Receivable, Allowance for Credit Loss	(381)	(138)
Accounts Receivable, Credit Loss Expense (Reversal)	(246)
Accounts Receivable, Allowance for Credit Loss, Writeoff	3
Contract with Customer, Asset, Allowance for Credit Loss [Roll Forward]
Contract with Customer, Asset, Allowance for Credit Loss	(188)	(81)
Contract with Customer, Asset, Credit Loss Expense (Reversal)	(107)
Contract with Customer, Asset, Allowance for Credit Loss, Writeoff
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss	(14)	(5)	$ (8)
Financing Receivable, Credit Loss, Expense (Reversal)	(9)
Financing Receivable, Allowance for Credit Loss, Writeoff
Other Current Assets
Allowance for Losses on Financial Assets [Line Items]
Allowance for Credit Loss	(48)	(38)
Credit Loss Expense, Reversal	(10)
Allowance for Credit Loss, Writeoff
Other Noncurrent Assets
Allowance for Losses on Financial Assets [Line Items]
Allowance for Credit Loss	(109)	$ (75)
Credit Loss Expense, Reversal	(34)
Allowance for Credit Loss, Writeoff