Accumulated Other Comprehensive Loss (Details) $ in Millions	6 Months Ended
	Jul. 31, 2021 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 14,440
Other comprehensive income before reclassifications, net of tax	1
Amounts reclassified from AOCI, net of tax	42
Ending balance	14,860
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(3)
Other comprehensive income before reclassifications, net of tax	1
Amounts reclassified from AOCI, net of tax	0
Ending balance	(2)
Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(18)
Other comprehensive income before reclassifications, net of tax	0
Amounts reclassified from AOCI, net of tax	0
Ending balance	(18)
Pension
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(735)
Other comprehensive income before reclassifications, net of tax	0
Amounts reclassified from AOCI, net of tax	42
Ending balance	(693)
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(756)
Ending balance	$ (713)