Stock-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Restricted stock awards, expense	$ 91us-gaap_RestrictedStockExpense	$ 84us-gaap_RestrictedStockExpense	$ 66us-gaap_RestrictedStockExpense
Stock options, expense	7us-gaap_StockOptionPlanExpense	8us-gaap_StockOptionPlanExpense	16us-gaap_StockOptionPlanExpense
Total stock-based compensation expense	98us-gaap_ShareBasedCompensation	92us-gaap_ShareBasedCompensation	82us-gaap_ShareBasedCompensation
Tax benefit recognized	(22)	(22)	(21)
Stock-based compensation expense, net of tax	$ 76	$ 70	$ 61

Stock-based compensation expense, net of tax

No definition available.

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- Details

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Definition

The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

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- Definition

The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

+ References

+ Details

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