Other Retirement Plans Other Retirement Plans (Schedule of Significant Multiemployer Plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	$ 29.1		$ 20.7		$ 22.6
Other Multi Employer Pension Plans [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	2.1		1.5		1.4
Multiemployer Plans, Pension [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	27.9		19.4		21.7
Multiemployer Plans, Pension [Member] | Pipeline Industry Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	8.9		6.2		10.3
Multiemployer plans, period contributions, significance of contributions	true
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2014
Entity tax identification number	736146433
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Central Pension Fund Of International Union Of Operating Engineers And Participating Employers [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	6.0		4.4		4.9
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	366052390
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Jan. 31, 2012		Jan. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Laborers National Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	1.5		0.5		0.2
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	751280827
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Teamsters National Pipeline Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	1.4		0		0
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	461102851
Multiemployer plan number	001
Multiemployer plans, certified zone status			NA	[1]
Multiemployer Plans, Pension [Member] | Eighth District Electrical Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	1.2		0.5		0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Feb. 28, 2013
Entity tax identification number	846100393
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Mar. 31, 2012		Mar. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	true
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | West Virginia Laborers Pension Trust Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.9		0.4		0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	556026775
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Mar. 31, 2012		Mar. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Michigan Laborers Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.9		0.2		0.2
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	386233976
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Yellow
Multiemployer plans, certified zone status, date	Aug. 31, 2012		Aug. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	true
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Operating Engineers Local 324 Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.8		0		0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	381900637
Multiemployer plan number	001
Multiemployer plans, certified zone status	Red		Red
Multiemployer plans, certified zone status, date	Apr. 30, 2012		Apr. 30, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | Laborers Local Union No. 158 Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.6		0.7		0.4
Multiemployer plans, period contributions, significance of contributions	true
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	236580323
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Laborers District Council Of West Pennsylvania Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.6		0.3		0.2
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	256135576
Multiemployer plan number	001
Multiemployer plans, certified zone status	Red		Yellow
Multiemployer plans, certified zone status, date	Dec. 31, 2012		Dec. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | International Brotherhood Of Electrical Workers Local 1249 Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.6		0.3		0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	May 05, 2013
Entity tax identification number	156035161
Multiemployer plan number	001
Multiemployer plans, certified zone status	Red		Red
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | International Union Of Operating Engineers Local 132 Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.5		0.3		0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	556015364
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Mar. 31, 2012		Mar. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Operating Engineers Construction Industry and Miscellaneous Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.5		0.1		0.2
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	256135579
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Yellow
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	true
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | International Union Of Operating Engineers Pension Fund Of Eastern Pennsylvania And Delaware [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.5		0.5		0.3
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	236405239
Multiemployer plan number	001
Multiemployer plans, certified zone status	Red		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2012		Dec. 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	Pending
Multiemployer Plans, Pension [Member] | Minnesota Laborers Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.4		0.3		1.0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	416159599
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | National Electrical Benefit Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.3		0.2		0.2
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	May 05, 2013
Entity tax identification number	530181657
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Southwestern Pennsylvania and Western Maryland Teamsters and Employers Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.3		0.1		0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	251046087
Multiemployer plan number	001
Multiemployer plans, certified zone status	Red		Red
Multiemployer plans, certified zone status, date	Jun. 30, 2012		Jun. 30, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | Laborers Pension Trust Fund For Northern Nevada [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.2		0.8		0.4
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	880138600
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	May 31, 2012		May 31, 2011
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Pension [Member] | Operating Engineers Pension Trust Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0		1.2		1.0
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	946090764
Multiemployer plan number	001
Multiemployer plans, certified zone status	Orange		Orange
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented
Multiemployer Plans, Pension [Member] | Central States Southeast And Southwest Areas Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0	[2]	0.9	[2]	0.8	[2]
Multiemployer plans, period contributions, significance of contributions	false	[2]
Multiemployer plans, surcharge	No	[2]
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014	[2]
Entity tax identification number	366044243	[2]
Multiemployer plan number	001	[2]
Multiemployer plans, certified zone status	Red	[2]	Red	[2]
Multiemployer plans, certified zone status, date	Dec. 31, 2011	[2]	Dec. 31, 2010	[2]
Multiemployer plans, certified zone status, extended amortization provisions	false	[2]
Multiemployer plans, funding improvement plan and rehabilitation plan	Implemented	[2]
Multiemployer Plans, Pension [Member] | Western Conference Of Teamsters Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0		0.4		0.3
Multiemployer plans, period contributions, significance of contributions	false
Multiemployer plans, surcharge	No
Multiemployer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Entity tax identification number	916145047
Multiemployer plan number	001
Multiemployer plans, certified zone status	Green		Green
Multiemployer plans, certified zone status, date	Dec. 31, 2011		Dec. 31, 2010
Multiemployer plans, certified zone status, extended amortization provisions	false
Multiemployer plans, funding improvement plan and rehabilitation plan	NA
Multiemployer Plans, Postretirement Benefit [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	1.2		1.3		0.9
Multiemployer Plans, Postretirement Benefit [Member] | New England Electrical Workers Money Purchase Plan And Trust [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	0.7	[3]	0.7	[3]	0.5	[3]
Multiemployer plans, surcharge	NA	[3]
Multiemployer plans, collective bargaining arrangement, expiration date	Aug. 30, 2012	[3],[4]
Multiemployer Plans, Postretirement Benefit [Member] | National Electrical Annuity Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	$ 0.3	[3]	$ 0.3	[3]	$ 0.4	[3]
Multiemployer plans, surcharge	NA	[3]
Multiemployer plans, collective bargaining arrangement, expiration date	Sep. 05, 2015	[3]

[1] Information not available as of December 31, 2012. The Teamsters National Pipeline Pension Fund was established in 2012.

[2] The Company’s subsidiary that participated in the Central States, Southeast and Southwest Areas Pension Plan voluntarily withdrew from this plan in November 2011. See additional discussion below and in Note 17 – Commitment and Contingencies.

[3] These plans are defined contribution multi-employer pension plans; therefore, PPA zone status disclosures in table below are not applicable.

[4] The collective bargaining agreement associated with the New England Electrical Workers Money Purchase Plan is under negotiation as of December 31, 2012.