Share Repurchase Plan - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2015	May. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Repurchase of outstanding common stock		$ 6,500	$ 4,000
Additional amount of common stock that may be repurchased	$ 1,150

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