Fair Value Measurements and Derivative Instruments (Income Statement) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fuel Expense	$ 713,676	$ 710,617		$ 681,118
Depreciation and amortization expenses	894,915	1,033,697		951,194		$ 894,915
Interest Income (Expense)	(286,514)	(300,872)		(269,881)
Other Income (Expense)	(35,653)	11,107	[1]	(5,289)	[1]	$ (35,653)	[1]
Fair value hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value hedge	12,275	4,673		6,065
Change in unrealized gain (loss) on fair value hedging instruments	3,863	(8,854)		(132)
Fair value hedging | Interest Rate Contract | Interest Expense
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value hedge	7,203	4,673
Change in unrealized gain (loss) on fair value hedging instruments	7,488	(8,854)		3,007
Fair value hedging | Interest Rate Contract | Other income (expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value hedge	5,072			6,065
Change in unrealized gain (loss) on fair value hedging instruments	(3,625)			(3,139)
Cash flow hedge | Interest Rate Contract | Interest Expense
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(41,480)	(10,931)		(31,603)
Cash flow hedge | Fuel contracts | Other income (expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	13,685	(1,580)		7,382
Cash flow hedge | Fuel contracts | Fuel cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(284,384)	1,366		(141,689)
Cash flow hedge | Foreign exchange contracts | Depreciation and amortization expenses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	(10,522)	(12,843)		(13,248)
Cash flow hedge | Foreign currency forward | Other income (expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain or (loss) reclassified from accumulated other comprehensive loss into income	$ (14,342)	$ 12,855		$ (9,472)

[1] For the year ended December 31, 2016, Other income (expense) included a $21.7 million loss related to the 2016 elimination of the Pullmantur reporting lag.