Flight Equipment Held for Sale (Details) - Aircraft Held For Sale $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2017 USD ($) aircraft	Dec. 31, 2016 USD ($) aircraft
Long Lived Assets Held-for-sale [Line Items]
Number of aircraft sold or agreed to be sold \| aircraft	1	6
Assets held for sale \| $	$ 42.5	$ 163.4

Amount of assets held-for-sale that are not part of a disposal group.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6390208&loc=d3e400-110220

Name:	us-gaap_AssetsHeldForSaleNotPartOfDisposalGroup
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant