Fair Value Measurements and Derivative Instruments - Recurring (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Liabilities:
Contingent consideration expense		$ 10,700	$ 0
Fair Value, Measurements, Recurring | Level 1
Assets:
Derivative financial instruments	[1],[2]	0		$ 0
Total Assets	[2]	0		0
Liabilities:
Derivative financial instruments	[2],[3]	0		0
Contingent consideration	[2],[4]	0		0
Total Liabilities	[2]	0		0
Fair Value, Measurements, Recurring | Level 2
Assets:
Derivative financial instruments	[1],[5]	30,883		65,297
Total Assets	[5]	30,883		65,297
Liabilities:
Derivative financial instruments	[3],[5]	385,576		201,812
Contingent consideration	[4],[5]	0		0
Total Liabilities	[5]	385,576		201,812
Fair Value, Measurements, Recurring | Level 3
Assets:
Derivative financial instruments	[1],[6]	0		0
Total Assets	[6]	0		0
Liabilities:
Derivative financial instruments	[3],[6]	0		0
Contingent consideration	[4],[6]	54,700		44,000
Total Liabilities	[6]	54,700		44,000
Total | Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments	[1]	30,883		65,297
Total Assets		30,883		65,297
Liabilities:
Derivative financial instruments	[3]	385,576		201,812
Contingent consideration	[4]	54,700		44,000
Total Liabilities		$ 440,276		$ 245,812

[1] Consists of foreign currency forward contracts, interest rate swaps and fuel swaps. Refer to the “Fair Value of Derivative Instruments” table for breakdown by instrument type.

[2] Inputs based on quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Valuation of these items does not entail a significant amount of judgment.

[3] Consists of foreign currency forward contracts, interest rate swaps and fuel swaps. Refer to the “Fair Value of Derivative Instruments” table for breakdown by instrument type.

[4] The contingent consideration related to the Silversea Cruises acquisition is estimated by applying a Monte-Carlo simulation method using our closing stock price along with significant inputs not observable in the market, including the probability of achieving the milestones and estimated future operating results. The Monte-Carlo simulation is a generally accepted statistical technique used to generate a defined number of valuation paths in order to develop a reasonable estimate of fair value. Refer to Note 3. Business Combination for further information on the Silversea Cruises acquisition. For the nine months ended September 30, 2019, we recorded a contingent consideration expense of $10.7 million within Other (expense) income in our consolidated statements of comprehensive income (loss).

[5] Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. For foreign currency forward contracts, interest rate swaps and fuel swaps, fair value is derived using valuation models that utilize the income valuation approach. These valuation models take into account the contract terms, such as maturity, as well as other inputs, such as foreign exchange rates and curves, fuel types, fuel curves and interest rate yield curves. Derivative instrument fair values take into account the creditworthiness of the counterparty and the Company.

[6] Inputs that are unobservable.