Commitments and Contingencies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) Aircraft
Types of Commercial Aircraft [Line Items]
Long-term Purchase Commitment, Minimum Quantity Required | Aircraft	25
Purchase Obligation, Future Minimum Payments, Remainder of Fiscal Year	$ 862,760
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required | Aircraft	64
Purchase Obligation, Due in Second Year	$ 52,518
Purchase Obligation, Due in Third Year	371,673
Purchase Obligation, Due in Fourth Year	375,216
Purchase Obligation, Due in Fifth Year	141,643
Purchase Obligation, Due after Fifth Year	0
Purchase Obligation	1,803,810
Pre-Delivery Payments [Member]
Types of Commercial Aircraft [Line Items]
Purchase Obligation	$ 129,218