Property, Plant, Equipment - Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Capitalized interest	$ 3,637	$ 2,725	$ 2,870
Depreciation expense	$ 46,428	$ 39,304	$ 35,703

The cumulative amount of depreciation (related to long-lived, depreciable flight assets owned by the entity and used in the entity's principle business operations and capitalized assets classified as property, plant and equipment that are owned by the entity) that has been recognized in the income statement.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentOwnedAccumulatedDepreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant