Fair Value Measurements and Derivative Instruments - Derivative Instruments (Details) € in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 EUR (€)	Dec. 31, 2014 USD ($)
Gains and losses from derivatives involved in hedging relationships
Percentage of aggregate cost exposed to fluctuations in the euro exchange rate	42.90%		42.90%		42.90%	28.80%
Interest rate swaps
Gains and losses from derivatives involved in hedging relationships
Notional amount	$ 3,600.0		$ 3,600.0			$ 2,900.0
Forward Contracts
Gains and losses from derivatives involved in hedging relationships
Change in fair value of foreign currency forward contracts recognized in earnings	11.2	$ 9.0	(16.9)	$ 10.8
Forward Contracts | Not Designated
Gains and losses from derivatives involved in hedging relationships
Notional amount	480.4		480.4
Forward Contracts | Designated as Hedging Instrument
Gains and losses from derivatives involved in hedging relationships
Notional amount	463.0		463.0		€ 415.6
Foreign exchange contracts
Gains and losses from derivatives involved in hedging relationships
Notional amount	2,500.0		2,500.0			$ 3,000.0
Cruise ships on order
Gains and losses from derivatives involved in hedging relationships
Aggregate cost of ships on order, not including TUI cruises and Project Edge ships on order			5,000.0
Amount deposited for cost of ships on order, including the conditional agreement for a third Quantum - class ship	$ 385.8		$ 385.8