Long-term Debt (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) aircraft	Dec. 31, 2015 USD ($)
Long-term Debt
Total debt	$ 1,959,838	$ 1,948,803
Unamortized debt issue cost, net	(20,747)	(20,902)
Total debt, net of debt issue costs	$ 1,939,091	$ 1,927,901
E 175
Long-term Debt
Number of aircraft delivered | aircraft	3
Debt issued to purchase of aircraft	$ 68,200
Debt instrument, term	12 years
Interest rate, minimum (as a percent)	3.60%
Interest rate, maximum (as a percent)	3.80%