Impact of Tax Cuts and Jobs Act on Previously Reported Balances of Prior Period Income Tax Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017
Prior Period Adjustments Restatement [Line Items]
Long-term income taxes	$ 30,050	$ 13,944	$ 13,485
Other long-term liabilities	$ 4,820	4,229	3,549
As Previously Reported
Prior Period Adjustments Restatement [Line Items]
Long-term income taxes		0	0
Other long-term liabilities		$ 18,173	$ 17,034