Commitments and Contingencies (Details) - USD ($) $ in Millions					1 Months Ended			3 Months Ended	9 Months Ended
	Oct. 18, 2022	Dec. 13, 2019	Jun. 04, 2019	Feb. 26, 2015	Mar. 31, 2016	Jun. 30, 2015	Aug. 31, 2013	Dec. 31, 2019	Sep. 30, 2022	Jul. 02, 2018	Mar. 31, 2018
Subsequent Event
Contingencies and Commitments
Loss contingency, damages paid, value	$ 34.6
Alaskan Way Viaduct Matter
Contingencies and Commitments
Ownership percentage in joint venture									45.00%
Value of claim filed					$ 57.2	$ 532.0
Value of counterclaim filed					$ 667.0
Settlement on judgment, awarded to other party		$ 57.2
Pre-tax charge, impact from jury verdict								$ 166.8
Pre-tax accrual, impact from jury verdict								$ 25.7
George Washington Bridge Bus Station Matter
Contingencies and Commitments
Value of claim filed				$ 30.0
Value of project							$ 100.0
Value of counterclaim filed in excess of											$ 113.0
Court issued writ of attachment amount			$ 23.0
Proof of claim amount		$ 113.0
Value of damages seeking										$ 113.0
George Washington Bridge Bus Station Matter | Return Of Retainage By Developer
Contingencies and Commitments
Value of counterclaim filed in excess of											$ 29.0
STP
Contingencies and Commitments
Ownership percentage in joint venture									45.00%