Fair Value Measurements and Derivative Instruments - Balance Sheet (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Asset Derivatives
Asset Derivatives		$ 221,258	$ 19,397
Liability Derivatives
Liability Derivatives		189,163	373,497
Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives	[1]	220,811	18,854
Liability Derivatives
Liability Derivatives	[1]	179,588	356,029
Not Designated as Hedging Instrument
Asset Derivatives
Asset Derivatives		447	543
Liability Derivatives
Liability Derivatives		9,575	17,468
Interest rate swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	1,760	5,246
Interest rate swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	52,611	57,679
Foreign currency forward contracts | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	136,534	0
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative Financial Instruments, Assets
Asset Derivatives
Asset Derivatives	[1]	45,583	0
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	4,479	68,165
Foreign currency forward contracts | Designated as Hedging Instrument | Derivative Financial Instruments, Liabilities
Liability Derivatives
Liability Derivatives	[1]	0	5,574
Fuel swaps | Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives	[1]	29,721	13,608
Fuel swaps | Designated as Hedging Instrument | Derivative Financial Instruments, Assets
Asset Derivatives
Asset Derivatives	[1]	7,213	0
Fuel swaps | Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives	[1]	40,517	95,125
Fuel swaps | Designated as Hedging Instrument | Derivative Financial Instruments, Liabilities
Liability Derivatives
Liability Derivatives	[1]	81,981	129,486
Fuel swaps | Not Designated as Hedging Instrument | Other assets
Asset Derivatives
Asset Derivatives		447	543
Fuel swaps | Not Designated as Hedging Instrument | Derivative Financial Instruments, Assets
Asset Derivatives
Asset Derivatives		0	0
Fuel swaps | Not Designated as Hedging Instrument | Other long-term Liabilities
Liability Derivatives
Liability Derivatives		2,223	5,936
Fuel swaps | Not Designated as Hedging Instrument | Derivative Financial Instruments, Liabilities
Liability Derivatives
Liability Derivatives		$ 7,352	$ 11,532

[1] Accounting Standard Codification 815-20 “Derivatives and Hedging.”