Special Charges (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) aircraft	Mar. 31, 2016 USD ($) aircraft
Property, Plant and Equipment [Line Items]
Purchase of property and equipment	$ 112,265	$ 159,829
Special charges	$ 4,776	$ 16,202
Aircraft [Member]
Property, Plant and Equipment [Line Items]
Number of previously leased aircraft purchased | aircraft		2
Purchase price		$ 44,000
Purchase of property and equipment		23,500
Value of noncash consideration		20,500
Fair value of assets acquired		27,400
Aircraft [Member] | Other Non-Cash Items [Member]
Property, Plant and Equipment [Line Items]
Value of noncash consideration		$ 400
Spare Engines [Member] | Spare Engines [Member]
Property, Plant and Equipment [Line Items]
Number of previously leased aircraft purchased | aircraft	1
Purchase price	$ 8,100
Purchase of property and equipment	3,800
Value of noncash consideration	4,300
Fair value of assets acquired	3,100
Special charges	4,800
Spare Engines [Member] | Spare Engines [Member] | Other Non-Cash Items [Member]
Property, Plant and Equipment [Line Items]
Value of noncash consideration	$ 200