Other Retirement Plans (Schedule of Multi-Employer Pension Plans) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)		$ 36.4		$ 48.2		$ 29.2
Multi-Employer Plans, Pension [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)		$ 31.9		44.6		27.9
Multi-Employer Plans, Pension [Member] | Central Pension Fund of the I.U.O.E and Participating Employers [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		366052390
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 6.5		$ 10.8		6.0
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date	[1]	Jan. 31, 2014		Jan. 31, 2013
Multi-employer Plans, extended amortization provisions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Pipeline Industry Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		736146433
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 4.8		$ 9.8		8.9
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 02, 2017
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date	[2]	Dec. 31, 2013		Dec. 31, 2012
Multi-employer plans, Company contributions greater than 5% of total plan contributions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Michigan Laborers' Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		386233976
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 2.1		$ 4.3		0.9
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Yellow		Yellow
Multi-employer plans, pension protection act zone status, date	[1]	Aug. 31, 2014		Aug. 31, 2013
Multi-employer Plans, extended amortization provisions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		Implemented
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Teamsters National Pipe Line Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		461102851
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 1.7		$ 2.7		1.4
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date	[2]	Dec. 31, 2013		Dec. 31, 2012
Multi-employer plans, Company contributions greater than 5% of total plan contributions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Operating Engineers' Local 324 Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		381900637
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 1.7		$ 4.5		0.8
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Red		Red
Multi-employer plans, pension protection act zone status, date		Apr. 30, 2014		Apr. 30, 2013
Multi-employer plans, funding improvement plan and rehabilitation plan status		Implemented
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | I.B.E.W. Local 769 Management Pension Plan A [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		866049763
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 1.6		$ 0.7		0.1
Multi-employer plans, collective bargaining arrangement, expiration date		Jul. 30, 2016
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date	[2]	Jun. 30, 2014		Jun. 30, 2013
Multi-employer plans, Company contributions greater than 5% of total plan contributions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Laborers' District Council of Western Pennsylvania Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		256135576
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 1.5		$ 0.4		0.6
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Red		Red
Multi-employer plans, pension protection act zone status, date		Dec. 31, 2013		Dec. 31, 2012
Multi-employer plans, funding improvement plan and rehabilitation plan status		Implemented
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Operating Engineers' Construction Industry and Misc. Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		256135579
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 1.2		$ 0.1		0.5
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date	[1]	Dec. 31, 2013		Dec. 31, 2012
Multi-employer Plans, extended amortization provisions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Laborers' Local Union No. 158 Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		236580323
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 1.0		$ 0.5		0.6
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date		Dec. 31, 2013		Dec. 31, 2012	[2]
Multi-employer plans, Company contributions greater than 5% of total plan contributions				true
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Eighth District Electrical Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		846100393
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 0.9		$ 2.2		1.3
Multi-employer plans, collective bargaining arrangement, expiration date		Feb. 28, 2018
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date		Mar. 31, 2014		Mar. 31, 2013
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | National Electrical Benefit Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		530181657
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 0.9		$ 0.2		0.0
Multi-employer plans, collective bargaining arrangement, expiration date		Dec. 31, 2015
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date		Dec. 31, 2013		Dec. 31, 2012
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Laborers' National Pension Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		751280827
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 0.8		$ 1.1		1.5
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Green		Green
Multi-employer plans, pension protection act zone status, date		Dec. 31, 2013		Dec. 31, 2012
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Midwest Operating Engineers Pension Trust Fund [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		366140097
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 0.7		$ 0.7		0.0
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Yellow		Yellow
Multi-employer plans, pension protection act zone status, date	[1]	Mar. 31, 2014		Mar. 31, 2013
Multi-employer Plans, extended amortization provisions		true		true
Multi-employer plans, funding improvement plan and rehabilitation plan status		Implemented
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | I.U.O.E. Pension Plan of Eastern Pennsylvania and Delaware [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, employer identification number		236405239
Multi-employer plans, plan number		001
Multi-employer plans, contributions (in dollars)		$ 0.6		$ 0.2		0.5
Multi-employer plans, collective bargaining arrangement, expiration date		Jun. 01, 2017
Multi-employer plans, pension protection act zone status		Green		Red
Multi-employer plans, pension protection act zone status, date		Dec. 31, 2013		Dec. 31, 2012
Multi-employer plans, funding improvement plan and rehabilitation plan status		NA
Multi-employer plans, surcharge status		No
Multi-Employer Plans, Pension [Member] | Other Funds [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)		$ 5.9	[3]	$ 6.4		$ 4.8
Multi-Employer Plans, Pension [Member] | Other Funds [Member] | Canadian Multi-Employer Plans [Member] | Canadian Dollars [Member]
Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)		$ 0.9

[1] This plan has utilized extended amortization provisions, which provide plans with extensions of time to amortize pension funding shortfalls.

[2] The Company’s contributions to this plan represent greater than 5% of the plan’s total contributions.

[3] Includes approximately $0.9 million U.S. dollars of contributions to Canadian multi-employer pension plans associated with the Company’s 2014 acquisition of Pacer, a Canadian company that employs union resources subject to collective bargaining agreements in connection with certain of its project work. Canadian multi-employer pension plans are not subject to the provisions of ERISA or the funding rules under the PPA that apply to U.S. registered multi-employer pension plans. Contributions to Canadian multi-employer pension plans are based on fixed amounts per hour per employee for employees covered under these plans.