Summary Of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2015 USD ($) Segment $ / shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Number of business groups \| Segment	4
Net increase in operating earnings from the impact of revisions in contract \| $	$ 222	$ 184	$ 351
Net increase in operating earnings per share from the quarterly impact of revisions in contract \| $ / shares	$ 0.44	$ 0.35	$ 0.65

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration