Basis of Presentation and Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Percentage of inventory valued using the LIFO method	70.00%		70.00%
Reduction to operating income	$ (100)	$ (100)	$ (188)	$ (194)
Accounting Standards Update 2017-07
Reduction to operating income		$ 17		$ 43

The percentage of LIFO (last in first out) inventory to total inventory as of the balance sheet date if other than 100 percent.

No definition available.

Name:	us-gaap_PercentageOfLIFOInventory
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant