Fair Value Measurements and Derivative Instruments - Recurring (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Assets:
Derivative financial instruments	$ 37,304		$ 96,949
Liabilities:
Derivative financial instruments	31,623		8,633
Fair Value, Measurements, Recurring | Total
Assets:
Derivative financial instruments	80,112	[1]	188,576	[1]
Investments	5,973	[2]	6,044	[2]
Total Assets	86,085		194,620
Liabilities:
Derivative financial instruments	74,431	[3]	100,260	[3]
Total Liabilities	74,431		100,260
Fair Value, Measurements, Recurring | Level 1
Assets:
Investments	5,973	[2],[4]	6,044	[2],[4]
Total Assets	5,973	[4]	6,044	[4]
Fair Value, Measurements, Recurring | Level 2
Assets:
Derivative financial instruments	80,112	[1],[5]	188,576	[1],[5]
Total Assets	80,112	[5]	188,576	[5]
Liabilities:
Derivative financial instruments	74,431	[3],[5]	100,260	[3],[5]
Total Liabilities	$ 74,431	[5]	$ 100,260	[5]

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

[2] Consists of exchange-traded equity securities and mutual funds.

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

[4] 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.

[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, cross currency 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. Fair value for foreign currency collar options is determined by using standard option pricing models with inputs based on the options’ contract terms, such as exercise price and maturity, and readily available public market data, such as foreign exchange curves, foreign exchange volatility levels and discount rates. All derivative instrument fair values take into account the creditworthiness of the counterparty and the Company.