Long-Term Debt And Notes Payable (Components Of Debt) (Parenthetical) (Detail)	3 Months Ended	12 Months Ended
Mar. 31, 2013	Dec. 31, 2012
5.50% Notes Due 2013
Debt Instrument [Line Items]
Debt instrument interest rate	5.50%	5.50%
Debt instrument maturity year	2013	2013
6.55% Notes Due 2036
Debt Instrument [Line Items]
Debt instrument interest rate	6.55%	6.55%
Debt instrument maturity year	2036	2036

Interest rate stated in the contractual debt agreement.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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