Accounting for and Classification of Discontinued Operations (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Dec. 31, 2011 item	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 CLX2 Service [Member]	Jun. 30, 2011 CLX2 Service [Member]	Jun. 30, 2012 CLX2 Service [Member]	Jun. 30, 2011 CLX2 Service [Member]	Sep. 30, 2011 CLX2 Service [Member]	Jun. 30, 2012 CLX2 Service [Member] Container and Charter Liabilities [Member]	Jun. 30, 2012 CLX2 Service [Member] Other Contractual Liabilities [Member]	Jun. 30, 2012 A&B	Jun. 30, 2011 A&B	Jun. 30, 2012 A&B	Jun. 30, 2011 A&B	Jun. 29, 2012 A&B	Jun. 30, 2012 A&B Continuing operations	Jun. 30, 2011 A&B Continuing operations	Jun. 30, 2012 A&B Continuing operations	Jun. 30, 2011 A&B Continuing operations	Jun. 30, 2011 A&B Discontinued operations	Jun. 30, 2012 A&B Discontinued operations	Jun. 30, 2011 A&B Discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of vessels used in discontinued operation										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										3
Duration of charter contracts (in years)										1
Fair value of obligations arising from exit activities						$ 1.8		$ 1.8			$ 1.8
Liabilities of Disposal Group, Including Discontinued Operation, Current [Roll Forward]
Balance, beginning of period								5.0			4.9	0.1
Expenses incurred								4.5			4.5		(77.2)	(64.0)	(118.1)	(106.0)
Amounts paid								(7.7)			(7.6)	(0.1)
Balance, end of period						1.8		1.8			1.8
Discontinued operations (net of tax) [Abstract]
Income from A&B													72.4	75.9	114.0	127.3
Expenses from A&B								4.5			4.5		(77.2)	(64.0)	(118.1)	(106.0)
Tax expense (benefit) related to A&B													0.4	(5.2)	0.1	(9.2)
Net (loss) income from A&B													(4.4)	12.3	(1.6)	22.1		(4.4)	6.7	(4.0)	12.1	5.6	2.4	10.0
CLX2 operating and shut down losses						(1.4)	(11.3)	(2.8)	(18.9)
Separation related tax expenses		(1.7)		(1.7)
(Loss) income from discontinued operations (net of tax)		(7.5)	1.0	(6.1)	3.2
Additional costs incurred, net of tax, not classified as discontinued operations						$ 0.1		$ 0.5