Employee Benefits (Tables)

12 Months Ended

Dec. 31, 2020

Retirement Benefits [Abstract]

Schedule of multi-employer plans

		Pension Protection										Expiration
		Act ("PPA")										of
	Employer	Certified Zone Status		FIP/RP								Collective
	Identification	(1)		Status	Contributions						Surcharge	Bargaining
Pension Trust Fund	Number	2020	2019	P/I (2)	2020		2019		2018		Imposed	Agreement
International Union of Operating Engineers - Employers Construction Industry Retirement Plan - Local 302 and 612 Trust Funds	91-6028571	Green	Green	N/A	$	2,480	$	3,021	$	2,482	—	2022
Washington Laborers	91-6022315	Green	Green	N/A	$	236	$	30	$	—	—	2023
Carpenters Retirement Plan of Western Washington	91-6029051	Green	Green	N/A	$	1,898	$	695	$	932	—	2022
Cement Masons & Plasterers Trust Funds	91-6066773	Green	Green	N/A	$	39	$	2	$	—	—	2023
Washington-Idaho-Montana Carpenters-Employers Retirement Trust Fund	91-6123987	Yellow	Yellow	I	$	—	$	36	$	—	—	2021
Engineers - AGC Retirement Trust of the Inland Empire	91-6070237	Yellow	Yellow	I	$	—	$	20	$	—	—	2021
Western Conference of Teamsters Pension Trust Fund	91-6145047	Green	Green	N/A	$	15	$	—	$	—	—	2023
Alaska Carpenters Trust Fund	92-0120866	Yellow	Yellow	I	$	271	$	377	$	328	—	2021
Alaska Laborers Trust Fund	91-6028298	Yellow	Yellow	I	$	226	$	552	$	321	—	2023

(1) The most recent PPA zone status available in 2020 and 2019 is for the plan’s year end during 2019 and 2018, respectively.  Zone status is based on information received from the plan and is indicative of the plans funding status. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded, and plans in the green zone are at least 80 percent funded.

(2) The FIP/RP Status P/I column indicates plans for which a financial improvement plan ("FIP") or a rehabilitation plan ("RP") is either pending ("P"), or implemented ("I").