Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Significant Accounting Policies
Gross amount of port costs included in passenger ticket revenues		$ 156.8	$ 155.0	$ 425.6	$ 416.8
Balance sheet reclass from Property, plant and equipment to Other assets
Significant Accounting Policies
Prior Period Reclassification Adjustment	$ 41.9
Cash flows reclass from Other, net to Net deferred income tax (benefit) expense
Significant Accounting Policies
Prior Period Reclassification Adjustment					$ 1.2