PROPERTY AND EQUIPMENT - SUMMARY (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and equipment
Cost	$ 2,151.9	$ 1,988.9
Accumulated depreciation of property and equipment	1,202.7	1,128.6
Property and equipment, net	949.2	860.3
Depreciation Expense	86.0	76.4	$ 66.8
Property and equipment subject to capital leases	6.4	6.4
Cost for construction of containerships	925.3
Capitalized interest	2.1	0.4	0.4
Net of accumulated depreciation	2.4	1.1
Amortization expenses	1.2	0.6	$ 0.3
Vessels
Property and equipment
Cost	1,416.1	1,384.8
Accumulated depreciation of property and equipment	840.7	787.4
Property and equipment, net	575.4	597.4
Containers and equipment
Property and equipment
Cost	536.9	496.0
Accumulated depreciation of property and equipment	326.7	307.8
Property and equipment, net	210.2	188.2
Terminal facilities and other property
Property and equipment
Cost	43.2	42.0
Accumulated depreciation of property and equipment	35.3	33.4
Property and equipment, net	7.9	8.6
Vessel construction in progress
Property and equipment
Cost	124.5	30.0
Property and equipment, net	124.5	30.0
Capitalized interest	2.9	0.8
Other construction in progress
Property and equipment
Cost	31.2	36.1
Property and equipment, net	$ 31.2	$ 36.1