Other Retirement Plans (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) employee	Sep. 30, 2020 USD ($) employee	Sep. 30, 2021 USD ($) employee	Sep. 30, 2020 USD ($) employee
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plan, employer contribution, cost	$ 48.6	$ 8.9	$ 103.0	$ 25.0
Pension
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plan, employer contribution, cost	36.9	7.2	81.1	19.5
Other Multiemployer
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plan, employer contribution, cost	$ 11.7	$ 1.7	$ 21.9	$ 5.5
Low
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, covered employees (in number of employees) | employee	5,116	1,452	2,412	1,119
High
Covered Employees and Contributions, Multiemployer Plans [Line Items]
Multiemployer plans, covered employees (in number of employees) | employee	6,979	1,469	6,979	1,469