Other Retirement Plans (Schedule of Multiemployer Pension Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	65-0829355
Multiemployer plans, contributions (in dollars)	$ 72.6	$ 99.7	$ 102.4
Multiemployer Plans, Pension [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, contributions (in dollars)	$ 66.9	92.4	92.1
Multiemployer Plans, Pension [Member] | Central Pension Fund Of IUOE And Participating Employers [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	36-6052390
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 12.6	$ 20.4	21.6
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Jan. 31, 2019	Jan. 31, 2018
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Pipeline Industry Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	73-6146433
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 9.6	$ 20.7	28.8
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | International Union of Operating Engineers Local 132 Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	55-6015364
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 5.0	$ 5.6	2.3
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Mar. 31, 2019	Mar. 31, 2018
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | West Virginia Laborers' Pension Trust Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	55-6026775
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 4.9	$ 4.5	3.0
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Mar. 31, 2019	Mar. 31, 2018
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Teamsters National Pipe Line Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	46-1102851
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 4.5	$ 7.4	7.6
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | IBEW Local 1249 Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	15-6035161
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 3.2	$ 2.2	1.5
Multiemployer plans, collective bargaining arrangement, expiration date	May 02, 2021
Multiemployer plans, pension protection act zone status	Green	Yellow
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Laborers' National Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	75-1280827
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 3.0	$ 4.1	3.5
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Red	Red
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Laborers' District Council of Western Pennsylvania Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	25-6135576
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.9	$ 1.4	0.6
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Yellow	Red
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Midwest Operating Engineers Pension Trust Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	36-6140097
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.8	$ 1.5	0.1
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Yellow	Yellow
Multiemployer plans, pension protection act zone status, date	Mar. 31, 2019	Mar. 31, 2018
Multiemployer plans, pension protection act zone status, extended amortization provisions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Employer- Teamsters Local Nos. 175 & 505 Pension Trust Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	55-6021850
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.7	$ 1.5	0.3
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Red	Red
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true
Multiemployer plans, pension protection act zone status, extended amortization provisions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Laborers' Local Union No. 158 Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	23-6580323
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.5	$ 1.5	1.8
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Laborers' Pension Fund of Roanoke, Virginia [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	54-6111015
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.5	$ 2.5	0.1
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Sep. 30, 2018	Sep. 30, 2017
Multiemployer plans, Company contributions greater than 5% of total plan contributions	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Laborers District Council & Contractors Pension Fund of Ohio [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	31-6129964
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.4	$ 1.8	2.5
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Central Laborers Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	37-6052379
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.3	$ 0.9	0.5
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Yellow	Yellow
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, pension protection act zone status, extended amortization provisions	true	true
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | National Electrical Benefit Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	53-0181657
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.2	$ 1.4	1.8
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Dec. 31, 2018	Dec. 31, 2017
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | National Electrical Benefit Fund [Member] | Maximum [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2021
Multiemployer Plans, Pension [Member] | Michigan Laborers Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	38-6233976
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 1.1	$ 1.5	2.0
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Yellow	Yellow
Multiemployer plans, pension protection act zone status, date	Aug. 31, 2019	Aug. 31, 2018
Multiemployer plans, pension protection act zone status, extended amortization provisions		true
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Ohio Operating Engineers Pension Plan [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	31-6129968
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 0.8	$ 2.1	4.9
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Green	Green
Multiemployer plans, pension protection act zone status, date	Jul. 31, 2018	Jul. 31, 2017
Multiemployer plans, funding improvement plan and rehabilitation plan status	NA
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Operating Engineers Local 324 Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, employer identification number	38-1900637
Multiemployer plans, plan number	001
Multiemployer plans, contributions (in dollars)	$ 0.0	$ 0.6	2.1
Multiemployer plans, collective bargaining arrangement, expiration date	May 31, 2020
Multiemployer plans, pension protection act zone status	Red	Red
Multiemployer plans, pension protection act zone status, date	Apr. 30, 2019	Apr. 30, 2018
Multiemployer plans, funding improvement plan and rehabilitation plan status	Implemented
Multiemployer plans, surcharge	No
Multiemployer Plans, Pension [Member] | Other Funds [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, contributions (in dollars)	$ 9.9	$ 10.8	7.1
CANADA | Multiemployer Plans, Pension [Member] | Other Funds [Member]
Multiemployer Plans [Line Items]
Multiemployer plans, contributions (in dollars)		$ 0.2	$ 0.7