Accounting for and Classification of Discontinued Operations: (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended				3 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 CLX2 Service	Sep. 30, 2011 CLX2 Service	Sep. 30, 2012 CLX2 Service	Sep. 30, 2011 CLX2 Service	Jul. 31, 2012 CLX2 Service	Jul. 31, 2012 CLX2 Service Container and charter liabilities item	Sep. 30, 2011 CLX2 Service Other contractual liabilities	Dec. 31, 2011 A&B item	Sep. 30, 2011 A&B	Sep. 30, 2012 A&B	Sep. 30, 2011 A&B	Jun. 29, 2012 A&B	Sep. 30, 2011 A&B Continuing operations	Sep. 30, 2012 A&B Continuing operations	Sep. 30, 2011 A&B Continuing operations	Sep. 30, 2011 A&B Discontinued operations	Sep. 30, 2012 A&B Discontinued operations	Sep. 30, 2011 A&B Discontinued operations
Accounting for and Classification of Discontinued Operations
Number of vessels used in discontinued operation									5		5
Number of publicly traded companies to be created after separation															2
Number of shares of common stock of A&B received for each share upon separation																			1
Number of vessels expected to be sub-chartered													2
Number of vessels returned to lessors												2		3
Duration of charter contracts														1 year
Income (losses) from discontinued operations
Income from A&B																$ 62.2	$ 114.0	$ 188.5
Expenses from A&B																(62.0)	(118.1)	(166.9)
Tax (expense) benefit from A&B																(0.1)	0.1	(9.3)
Net (loss) income from A&B																4.4	(1.6)	26.6		0.1	(4.0)	12.3	4.3	2.4	14.3
CLX2 operating and shutdown (losses)								0.1	(14.1)	(2.7)	(33.1)
Separation related tax expenses					(1.7)
(Loss) income from discontinued operations (net of tax)	0.1	(9.7)			(6.0)	(6.5)
Additional costs incurred, net of tax, not classified as discontinued operations									6.1	0.5	6.1
Effect of reclassification adjustment on cash flows provided by operating activities from continuing operations			6.0	15.6
Effect of reclassification adjustment on current liabilities related to discontinued operations							5.1
Effect of reclassification adjustment on current assets related to discontinued operations							2.1
Effect of reclassification adjustment on Uninsured Claims related to discontinued operations							0.1
Effect of reclassification adjustment on Accrued and Other liabilities related to discontinued operations							$ 5.0