Commitments and Contingencies - Sale Leaseback Transactions Aircraft (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013 aircraft_engine aircraft
Commitments and Contingencies Disclosure [Abstract]
Number of aircrafts delivered	4
Number of aircrafts financed with direct operating leases	2
Number of spare aircraft engines entered into sale and leaseback agreement	1
Aircraft [Member]
Sale Leaseback Transaction [Line Items]
Number of aircraft entered into sale and leaseback agreement	2
Sale leaseback transaction on aircraft, net deferred gain (loss)	(0.4)
Sale leaseback transaction on aircraft, refund in pre-delivery deposits	12.0

The portion of the gain that will be recorded as income or a reduction in rent expense in future periods less amounts recognized in the current period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 33

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 35

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=21918046&loc=d3e50609-112754

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