Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Minimum future rental commitments under operating leases having noncancelable lease terms
2012	$ 14,188
2013	8,151
2014	6,678
2015	5,806
2016	4,825
Thereafter	15,927
Total	55,575
Schedule Of Guarantees [Abstract]
Maximum potential undiscounted payments	389,606
Performance guarantees through letters of credit [Member]
Schedule Of Guarantees [Abstract]
Term	2012-2016
Maximum potential undiscounted payments	246,197
Standby letters of credit [Member]
Schedule Of Guarantees [Abstract]
Term	2012
Maximum potential undiscounted payments	15,921
Bid bonds and performance bonds [Member]
Schedule Of Guarantees [Abstract]
Term	2012-2018
Maximum potential undiscounted payments	$ 127,488

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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-Name FASB Interpretation (FIN)

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-Paragraph 13

-Subparagraph b

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Describe the approximate term of the guarantee or each group of similar guarantees.

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 13

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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-Publisher FASB

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The total of future contractually required payments on leases defined as operating.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 122

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-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.

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-Name Accounting Standards Codification

-Topic 840

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-Section 55

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-Section 50

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

+ References

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fifth year of the balance sheet date relating to leases defined as operating.

+ References

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fourth year of the balance sheet date relating to leases defined as operating.

+ References

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the third year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the second year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due after the fifth year from the balance sheet date on leases defined as operating.

+ References

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