Fair Value Measurements and Derivative Instruments - Recurring (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
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
Level 2
Assets:
Derivative financial instruments	[1],[5]	39,045	39,994
Total Assets	[5]	39,045	39,994
Liabilities:
Derivative financial instruments	[3],[5]	404,284	257,728
Contingent consideration	[4],[5]	0	0
Total Liabilities	[5]	404,284	257,728
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]	17,795	62,400
Total Liabilities	[6]	17,795	62,400
Total
Assets:
Derivative financial instruments	[1]	39,045	39,994
Total Assets		39,045	39,994
Liabilities:
Derivative financial instruments	[3]	404,284	257,728
Contingent consideration	[4]	17,795	62,400
Total Liabilities		$ 422,079	$ 320,128

[1] Consists of foreign currency forward contracts, interest rate swaps and fuel swaps. 

[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.

[4] The contingent consideration related to the 2018 Silversea Cruises acquisition was 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.

[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.