Debt - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2013
Debt Outstanding [Line Items]
Percentage of owned subsidiaries guaranteed	100.00%
Multi-Year Facility, Expiring July 2016
Debt Outstanding [Line Items]
Expiration dates	2016-07
Multi Year Facility Expiring July Two Thousand Thirteen [Member]
Debt Outstanding [Line Items]
Expiration dates	2018-07
Commercial Paper
Debt Outstanding [Line Items]
Percentage of owned subsidiaries guaranteed	100.00%
Commercial paper	$ 0
Commercial paper, at carrying value	500,000,000
Credit facilities	2,000,000,000
Remaining borrowing capacity	280,000,000
Commercial Paper \| Multi-Year Facility, Expiring July 2016
Debt Outstanding [Line Items]
Credit facilities	1,000,000,000
Commercial Paper \| Multi Year Facility Expiring July Two Thousand Thirteen [Member]
Debt Outstanding [Line Items]
Credit facilities	$ 1,000,000,000

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Unsecured short-term debt instrument issued by corporations which are highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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