Other Retirement Plans (Schedule of Significant Multi-Employer Pension Plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Multi-Employer Plans [Line Items]
Multi-employer plan, contributions	$ 48.2		$ 29.2		$ 20.7
Multi-Employer Plans, Pension [Member]
Multi-Employer Plans [Line Items]
Multi-employer plan, contributions	44.6		27.9		19.5
Multi-Employer Plans, Pension [Member] | Central Pension Fund of IUOE and Participating Employers [Member]
Multi-Employer Plans [Line Items]
Employer identification number	366052390
Multi-employer plan number	001
Multi-employer plan, contributions	10.8		6.0		4.4
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Jan. 31, 2013	[1]	Jan. 31, 2012	[1]
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]
Employer identification number	736146433
Multi-employer plan number	001
Multi-employer plan, contributions	9.8		8.9		6.2
Multi-employer plans, collective bargaining arrangement, expiration date	May 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012	[2]	Dec. 31, 2011	[2]
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]
Employer identification number	381900637
Multi-employer plan number	001
Multi-employer plan, contributions	4.5		0.8		0
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Red		Red
Multi-employer plans, pension protection act zone status, date	Apr. 30, 2013		Apr. 30, 2012
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented
Multi-employer plans, surcharge status	Yes
Multi-Employer Plans, Pension [Member] | Michigan Laborers Pension Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	386233976
Multi-employer plan number	001
Multi-employer plan, contributions	4.3		0.9		0.2
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Yellow		Green
Multi-employer plans, pension protection act zone status, date	Aug. 31, 2013	[1]	Aug. 31, 2012
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented
Multi-employer plans, surcharge status	No
Multi-Employer Plans, Pension [Member] | Teamsters National Pipeline Pension Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	461102851	[3]
Multi-employer plan number	001	[3]
Multi-employer plan, contributions	2.7	[3]	1.4	[3]	0	[3]
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014	[3]
Multi-employer plans, pension protection act zone status	Green	[3]	NA	[3]
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012	[2],[3]
Multi-employer plans, funding improvement plan and rehabilitation plan status	NA	[3]
Multi-employer plans, surcharge status	No	[3]
Multi-Employer Plans, Pension [Member] | Eighth District Electrical Pension Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	846100393
Multi-employer plan number	001
Multi-employer plan, contributions	2.2		1.3		0.5
Multi-employer plans, collective bargaining arrangement, expiration date	Feb. 28, 2015
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Mar. 31, 2013		Mar. 31, 2012	[1]
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented
Multi-employer plans, surcharge status	No
Multi-Employer Plans, Pension [Member] | Laborers National Pension Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	751280827
Multi-employer plan number	001
Multi-employer plan, contributions	1.1		1.5		0.5
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012		Dec. 31, 2011
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 and Contractors Pension Fund of Ohio [Member]
Multi-Employer Plans [Line Items]
Employer identification number	316129964
Multi-employer plan number	001
Multi-employer plan, contributions	0.7		0.1		0.1
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012		Dec. 31, 2011
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]
Employer identification number	366140097
Multi-employer plan number	001
Multi-employer plan, contributions	0.7		0		0
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Yellow		Green
Multi-employer plans, pension protection act zone status, date	Mar. 31, 2013	[1]	Mar. 31, 2012	[1]
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented
Multi-employer plans, surcharge status	Yes
Multi-Employer Plans, Pension [Member] | I.B.E.W. Local 769 Management Pension Plan A [Member]
Multi-Employer Plans [Line Items]
Employer identification number	866049763
Multi-employer plan number	001
Multi-employer plan, contributions	0.7		0.1		0
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	Jun. 30, 2012		Jun. 30, 2011	[2]
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]
Employer identification number	236580323
Multi-employer plan number	001
Multi-employer plan, contributions	0.5		0.6		0.7
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012	[2]	Dec. 31, 2011	[2]
Multi-employer plans, funding improvement plan and rehabilitation plan status	NA
Multi-employer plans, surcharge status	No
Multi-Employer Plans, Pension [Member] | West Virginia Laborers Pension Trust Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	556026775
Multi-employer plan number	001
Multi-employer plan, contributions	0.5		0.9		0.4
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	Mar. 31, 2013		Mar. 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 District Council of Western Pennsylvania Pension Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	256135576
Multi-employer plan number	001
Multi-employer plan, contributions	0.4		0.6		0.3
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Red		Yellow
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012		Dec. 31, 2011
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented
Multi-employer plans, surcharge status	Yes
Multi-Employer Plans, Pension [Member] | Laborers Pension Trust Fund for Northern Nevada [Member]
Multi-Employer Plans [Line Items]
Employer identification number	880138600
Multi-employer plan number	001
Multi-employer plan, contributions	0.1		0.2		0.8
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Green		Green
Multi-employer plans, pension protection act zone status, date	May 31, 2013		May 31, 2012	[2]
Multi-employer plans, funding improvement plan and rehabilitation plan status	NA
Multi-employer plans, surcharge status	No
Multi-Employer Plans, Pension [Member] | Operating Engineers Pension Trust Fund [Member]
Multi-Employer Plans [Line Items]
Employer identification number	946090764
Multi-employer plan number	001
Multi-employer plan, contributions	0		0		1.2
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014
Multi-employer plans, pension protection act zone status	Orange		Orange
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012		Dec. 31, 2011
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented
Multi-employer plans, surcharge status	Yes
Multi-Employer Plans, Pension [Member] | Central States Southeast and Southwest Areas Pension Plan [Member]
Multi-Employer Plans [Line Items]
Employer identification number	366044243	[4]
Multi-employer plan number	001	[4]
Multi-employer plan, contributions	0	[4]	0	[4]	0.9	[4]
Multi-employer plans, collective bargaining arrangement, expiration date	Jan. 31, 2014	[4]
Multi-employer plans, pension protection act zone status	Red	[4]	Red	[4]
Multi-employer plans, pension protection act zone status, date	Dec. 31, 2012	[4]	Dec. 31, 2011	[4]
Multi-employer plans, funding improvement plan and rehabilitation plan status	Implemented	[4]
Multi-employer plans, surcharge status	No	[4]
Multi-Employer Plans, Pension [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multi-Employer Plans [Line Items]
Multi-employer plan, contributions	$ 5.6		$ 4.6		$ 3.3

[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] The Teamsters National Pipeline Pension Fund was established in 2012.

[4] 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 discussion below and in Note 16 – Commitments and Contingencies.