Stockholders' Equity - Additional Information (Detail) - Share Repurchase Program 2016 - USD ($)	Sep. 30, 2018	Sep. 20, 2016
Share Repurchases [Line Items]
Amount available for repurchase under the share repurchase program approved by the company's Board of Directors		$ 40,000,000,000
Unused amount of share repurchase program	$ 25,600,000,000

Amount remaining of a stock repurchase plan authorized.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant