PENSION AND POST-RETIREMENT PLANS - MULTI-EMPLOYER DEFINED BENEFIT PLANS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2012
Multiemployer Plans
Multiemployer Plans, Accumulated Benefit Obligation	$ 244.2
Minimum
Multiemployer Plans
Employer matching contribution to MEBA Pension Trust (as a percent)				11.70%
Multiemployer Benefit Pension Plans
Multiemployer Plans
Contributions of Matson	$ 25.5	$ 24.4	$ 22.7
Multiemployer Benefit Pension Plans | Minimum | Green Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	80.00%
Multiemployer Benefit Pension Plans | Maximum | Red Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	65.00%
Multiemployer Benefit Pension Plans | Maximum | Yellow Zone
Multiemployer Plans
Funded status of multiemployer plan (as a percent)	80.00%
Multiemployer Benefit Pension Plans | American Radio Association Pension Fund | Green Zone
Multiemployer Plans
Contributions of Matson	$ 1.0	1.0
Multiemployer Benefit Pension Plans | Hawaii Terminals Multiemployer Pension Plan | Yellow Zone
Multiemployer Plans
Contributions of Matson	5.7	5.7	5.3
Multiemployer Benefit Pension Plans | Hawaii Stevedoring Multiemployer Retirement Plan | Yellow Zone
Multiemployer Plans
Contributions of Matson	4.3	3.8	3.5
Multiemployer Benefit Pension Plans | Master Mates And Pilots Pension Plan | Green Zone
Multiemployer Plans
Contributions of Matson	3.0	3.0	3.1
Multiemployer Benefit Pension Plans | Masters, Mates and Pilots Adjustable Pension Plan
Multiemployer Plans
Contributions of Matson	1.7	1.7	1.8
Multiemployer Benefit Pension Plans | O C U Trust Pension Plan | Green Zone
Multiemployer Plans
Contributions of Matson	0.2	0.2	0.2
Multiemployer Benefit Pension Plans | SIU Pacific District Pension Plan | Green Zone
Multiemployer Plans
Contributions of Matson	1.2	0.7	0.6
Multiemployer Benefit Pension Plans | Alaska Teamster - Employer Pension Plan | Red Zone
Multiemployer Plans
Contributions of Matson	1.9	2.4	2.6
Multiemployer Benefit Pension Plans | All Alaska Longshore Pension Plan | Green Zone
Multiemployer Plans
Contributions of Matson	1.0	0.1	0.1
Multiemployer Benefit Pension Plans | Western Conference of Teamsters Pension Plan | Green Zone
Multiemployer Plans
Contributions of Matson	1.4	1.3	1.3
Multiemployer Benefit Pension Plans | O P E I U Local 153 Pension Plan | Red Zone
Multiemployer Plans
Contributions of Matson	0.1	0.1	0.1
Multiemployer Benefit Postretirement Plans
Multiemployer Plans
Contributions of Matson	30.0	27.0	22.5
Multi-employer defined contribution pension plans | M E B A Pension Trust - Defined Benefit Plan | Red Zone
Multiemployer Plans
Contributions of Matson		$ 4.4
Multi-employer defined contribution pension plans | M E B A Pension Trust - Defined Benefit Plan | Green Zone
Multiemployer Plans
Contributions of Matson	$ 4.0		$ 4.1