Fair Value Measurements and Derivative Instruments (Details 4)	6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Jun. 30, 2013 Unsecured senior notes 5.625% due 2014 EUR (€)	Jun. 30, 2013 Forward Contracts USD ($)	Jun. 30, 2012 Forward Contracts USD ($)	Jun. 30, 2013 Forward Contracts USD ($)	Jun. 30, 2012 Forward Contracts USD ($)	Jun. 30, 2013 Foreign currency forward EUR (€)
Gains and losses from derivatives involved in hedging relationships
Aggregate cost of ships on order, including the conditional agreement for a third Quantum - class ship	$ 4,500,000,000
Amount deposited for cost of ships on order, including the conditional agreement for a third Quantum - class ship	288,800,000
Percentage of aggregate cost exposed to fluctuations in the euro exchange rate	56.40%	49.70%
Amount of foreign currency forward contracts designated as cash flow hedge								365,000,000
Long term debt, principal amount			745,000,000
Interest rate on debt instrument (as a percent)			5.625%
Amount of foreign currency forward contracts not designated as hedging instruments				360,000,000		360,000,000
Change in fair value of foreign currency forward contracts recognized in earnings				(16,900,000)	(4,100,000)	(25,500,000)	4,200,000
Notional amount of outstanding foreign exchange contracts	$ 1,600,000,000	$ 1,200,000,000