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Employee Benefit Plans (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 National Electrical Annuity Plan	Dec. 31, 2011 National Electrical Annuity Plan	Dec. 31, 2010 National Electrical Annuity Plan	Dec. 31, 2012 Eighth District Electrical Pension Fund Annuity Plan	Dec. 31, 2011 Eighth District Electrical Pension Fund Annuity Plan	Dec. 31, 2010 Eighth District Electrical Pension Fund Annuity Plan	Dec. 31, 2012 National Electrical Benefit Fund	Dec. 31, 2011 National Electrical Benefit Fund	Dec. 31, 2010 National Electrical Benefit Fund	Dec. 31, 2012 Eighth District Electrical Pension Fund	Dec. 31, 2011 Eighth District Electrical Pension Fund	Dec. 31, 2010 Eighth District Electrical Pension Fund	Dec. 31, 2012 IBEW Local 1249 Pension Plan	Dec. 31, 2011 IBEW Local 1249 Pension Plan	Dec. 31, 2010 IBEW Local 1249 Pension Plan	Dec. 31, 2012 All other funds:	Dec. 31, 2011 All other funds:	Dec. 31, 2010 All other funds:	Dec. 31, 2012 Multiemployer pension plans Maximum	Dec. 31, 2012 Multiemployer pension plans Minimum item	Mar. 31, 2012 Multiemployer pension plans Minimum Eighth District Electrical Pension Fund	Mar. 31, 2011 Multiemployer pension plans Minimum Eighth District Electrical Pension Fund	Mar. 31, 2010 Multiemployer pension plans Minimum Eighth District Electrical Pension Fund	Dec. 31, 2012 Multiemployer pension plans Minimum IBEW Local 1249 Pension Plan	Dec. 31, 2010 Multiemployer pension plans Minimum IBEW Local 1249 Pension Plan
Multiemployer pension plans
Number of local unions																							100
Percentage funded for red zone																						65.00%
Percentage funded for yellow zone																						80.00%
Percentage funded for green zone																							80.00%
Significant multiemployer plans
Contributions to Plan	$ 39,763,000	$ 33,140,000	$ 30,795,000	$ 17,081,000	$ 14,564,000	$ 10,263,000	$ 2,560,000	$ 2,429,000	$ 3,065,000	$ 5,731,000	$ 5,138,000	$ 4,187,000	$ 3,733,000	$ 3,752,000	$ 4,605,000	$ 3,679,000	$ 2,749,000	$ 3,933,000	$ 6,979,000	$ 4,508,000	$ 4,742,000
Minimum future contributions (as a percent)										3.00%
Minimum future contributions (in dollars per hour)													$ 1.71			$ 9.60
Percentage of total contribution to the plan																								5.00%	5.00%	5.00%	5.00%	5.00%

X

- Definition

Represents the percentage funded for green zone status.

+ References

No definition available.

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- Definition

Amount of minimum contribution(s) as a percent of wages required for future periods to a multiemployer plan by collective bargaining arrangements, statutory obligations, or other contractual obligations. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

No definition available.

+ Details

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X

- Definition

Represents the percentage funded for red zone status.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage funded for yellow zone status.

+ References

No definition available.

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X

- Definition

Represents information pertaining to number of locals covered under multiemployer defined plan.

+ References

No definition available.

+ Details

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- Definition

Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450702-114947



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450691-114947



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

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- Definition

Percentage of contributions required by a collective bargaining arrangement to all contributions required of an employer related to a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

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- Definition

Amount of minimum contribution(s) required for future periods to a multiemployer plan by collective bargaining arrangements, statutory obligations, or other contractual obligations. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (f)(3)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450657-114947

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