Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 803,632	$ 632,784
Total assets	803,632	637,587
Total liabilities	0	1,141
Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps		1,141
Jet fuel options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Jet fuel options		4,803
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	803,632	632,784
Total assets	803,632	632,784
Total liabilities	0	0
Level 1 | Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps		0
Level 1 | Jet fuel options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Jet fuel options		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total assets	0	0
Total liabilities	0	1,141
Level 2 | Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap, liability		1,100
Interest rate swaps		1,141
Level 2 | Jet fuel options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Jet fuel options		0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total assets	0	4,803
Total liabilities	$ 0	0
Level 3 | Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps		0
Level 3 | Jet fuel options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Jet fuel options		$ 4,803