COVID-19 Pandemic, CARES Funding (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		14 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Apr. 29, 2021
CARES Funds Received [Line Items]
Total Expected Relief From PSP of CARES Act						$ 2,270
Adjustments to Additional Paid in Capital, Warrant Issued						25
Total Unsecured Term Loan through PSP of CARES Act						600
CARES Act Payroll Tax Relief				$ 21
ProceedsFromPayrollSupportProgramGrant						1,645
PSPGrantRecognized	$ 503		$ (362)	914	$ (362)
CARES PSP 1 [Member]
CARES Funds Received [Line Items]
Total Expected Relief From PSP of CARES Act						1,059
Adjustments to Additional Paid in Capital, Warrant Issued						9
Total Unsecured Term Loan through PSP of CARES Act						293
ProceedsFromPayrollSupportProgramGrant						757
PSP Installments Received				8
CARES PSP 2 [Member]
CARES Funds Received [Line Items]
Total Expected Relief From PSP of CARES Act						626
Adjustments to Additional Paid in Capital, Warrant Issued				16		9
Total Unsecured Term Loan through PSP of CARES Act				311		160
Additional Relief from PSP of CARES Act							$ 80
ProceedsFromPayrollSupportProgramGrant				$ 892		457
PSP Installments Received		$ 539
CARES PSP 3 [Member]
CARES Funds Received [Line Items]
Total Expected Relief From PSP of CARES Act	$ 585
Adjustments to Additional Paid in Capital, Warrant Issued						7
Total Unsecured Term Loan through PSP of CARES Act						147
ProceedsFromPayrollSupportProgramGrant						$ 431