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Line of Credit and Capital Lease Obligations (Narrative) (Detail) (USD $) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2012 | Nov. 19, 2012
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Line of Credit facility, borrowing capacity | $ 800,000,000 | $ 500,000,000
Line of Credit facility, maturity date | Nov. 17, 2017 |
Line of Credit facility, estimated increase in borrowings | 1,000,000,000 |
Line of Credit facility, outstanding principal balance | 144,000,000 |
Line of Credit facility, reduction in the available balance | 5,500,000 |
Letters of credit, weighted average interest rate | 1.30% |
Line of Credit facility, available balance | 650,500,000 |
Letter of Credit [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Line of Credit facility, borrowing capacity | 75,000,000 |
Swingline Loans [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Line of Credit facility, borrowing capacity | $ 37,500,000 |
Federal Funds Rate [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Debt instrument, interest rate | 0.50% |
Libor [Member] | Maximum [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Debt instrument, interest rate, as defined in the Line of Credit | 1.00% |
Libor [Member] | Maximum [Member] | Applicable Margin Rate [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Debt instrument, interest rate, as defined in the Line of Credit | 0.75% |
Libor [Member] | Maximum [Member] | Alternate Base Rate [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Debt instrument, interest rate, as defined in the Line of Credit | 1.75% |
Libor [Member] | Minimum [Member] | Applicable Margin Rate [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Debt instrument, interest rate, as defined in the Line of Credit | 0.125% |
Libor [Member] | Minimum [Member] | Alternate Base Rate [Member] |  |
Line Of Credit Facility Covenant Compliance [Line Items] |  |
Debt instrument, interest rate, as defined in the Line of Credit | 1.125% |

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- Definition Line Of Credit Facility Potential Increase In Borrowing Capacity + References No definition available. + Details
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- Definition Line of credit facility, reduction in the available balance + References No definition available. + Details
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- Definition The percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition The average effective interest rate during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 3: 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 + Details
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- Definition Amount borrowed under the credit facility as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Definition Date the credit facility terminates, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Definition Maximum amount borrowed under the credit facility at any time during the period. + References No definition available. + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. 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 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Definition Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of long-term debt outstanding by type or by instrument at that time. + References No definition available. + Details
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