Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities:
Net income	$ 232.0	$ 81.4	$ 103.0
Reconciling adjustments:
Depreciation and amortization	101.2	97.1	83.4
Deferred income taxes	(128.9)	24.7	50.7
Loss on disposal of property	3.0	0.9	1.2
Share-based compensation expense	11.1	11.2	12.2
Equity in income of Terminal Joint Venture	(28.2)	(15.8)	(16.5)
Distributions from Terminal Joint Venture	17.5		14.0
Tax benefit from equity issuance		2.2	2.6
Tax benefit from stock-based compensation		(0.3)	(0.9)
Changes in assets and liabilities:
Accounts receivable, net	(5.1)	14.4	13.5
Deferred dry-docking payments	(54.6)	(59.2)	(25.7)
Deferred dry-docking amortization	46.2	38.9	23.1
Prepaid expenses and other assets	14.4	(13.6)	(13.2)
Accounts payable, accruals and other liabilities	20.4	2.1	(9.4)
Other long-term liabilities	(4.1)	(26.2)	7.3
Net cash provided by operating activities	224.9	157.8	245.3
Cash Flows From Investing Activities:
Capitalized vessel construction expenditures	(252.0)	(94.5)	(21.3)
Other capital expenditures	(55.0)	(84.9)	(46.5)
Proceeds from (payments for) disposal of property and equipment	(0.2)	2.5	5.5
Cash deposits into Capital Construction Fund	(171.4)	(123.4)	(77.9)
Withdrawals from Capital Construction Fund	201.7	92.2	105.4
Payments for membership interests in Span Alaska, net of cash acquired		(112.6)
Payments for Horizon’s common stock, net of cash acquired, and other acquisitions			(29.0)
Net cash used in investing activities	(276.9)	(320.7)	(63.8)
Cash Flows From Financing Activities:
Proceeds from issuance of debt		275.0	75.0
Payments of debt	(30.0)	(20.5)	(20.5)
Repayment of capital leases	(1.8)	(1.7)	(1.5)
Proceeds from revolving credit facility	469.0	1,103.0	588.0
Repayments of revolving credit facility	(319.0)	(1,048.0)	(588.0)
Payment of financing costs	(1.7)		(0.9)
Proceeds from issuance of common stock	1.9	1.2	2.2
Dividends paid	(33.8)	(32.2)	(30.8)
Repurchase of Matson common stock	(19.3)	(38.0)	(4.9)
Tax withholding related to net share settlements of restricted stock units	(7.4)	(5.9)	(2.9)
Tax benefit from stock-based compensation		0.3	0.9
Payments of Span Alaska debt		(81.9)
Payments of Horizon debt and redemption of warrants, net			(466.0)
Net cash provided by (used in) financing activities	57.9	151.3	(449.4)
Net Increase (Decrease) in Cash and Cash Equivalents	5.9	(11.6)	(267.9)
Cash and Cash Equivalents, Beginning of the Year	13.9	25.5	293.4
Cash and Cash Equivalents, End of the Year	19.8	13.9	25.5
Supplemental Cash Flow Information:
Interest paid, net of capitalized interest	23.9	21.6	17.7
Income tax paid, net of income tax rrefunds	2.6	15.6	40.0
Non-cash Information:
Capital expenditures included in accounts payable, accruals and other liabilities	$ 1.2	$ 4.1	13.5
Capital lease obligations			$ 1.8