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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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Debt - Long-Term Debt and Short-Term Borrowings (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Long-term debt and short-term borrowings
Long-term debt			$ 10
Long-term Debt, Total	1,266	1,275
Less current maturities	(2)	(2)
Long-term debt	1,264	1,273
Revolving Credit Facility, maturing 2018 [Member]
Long-term debt and short-term borrowings
Credit agreement
Senior Notes, interest at 7.375%, maturing 2015 [Member]
Long-term debt and short-term borrowings
Senior Notes	294	294
Senior Notes, interest at 6.75%, maturing 2018 [Member]
Long-term debt and short-term borrowings
Senior Notes	371	371
Senior Notes, interest at 7.15%, maturing 2019 [Member]
Long-term debt and short-term borrowings
Senior Notes	206	206
Senior Notes, interest at 3.125%, maturing 2023 [Member]
Long-term debt and short-term borrowings
Senior Notes	349	349
Mortgages and other, interest rates ranging from 1.00% to 9.00%, various maturities [Member]
Long-term debt and short-term borrowings
Long-term debt	$ 46	$ 55