Summary of Significant Accounting Policies - Property and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Depreciation, Depletion and Amortization, Nonproduction [Abstract]
Depreciation	$ 6,156,000	$ 5,186,000	$ 4,313,000
Amortization of heavy maintenance	9,100,000	2,574,000	1,307,000
Total depreciation and amortization	15,256,000	7,760,000	5,620,000
Other equipment and vehicles | Minimum
Property, Plant and Equipment [Line Items]
Depreciable lives used for the principal depreciable asset classifications	5 years
Other equipment and vehicles | Maximum
Property, Plant and Equipment [Line Items]
Depreciable lives used for the principal depreciable asset classifications	7 years
Internally developed software
Depreciation, Depletion and Amortization, Nonproduction [Abstract]
Depreciation	3,200,000	2,000,000	1,100,000
Capitalized software development costs during the year	$ 2,300,000	$ 3,300,000	$ 2,400,000
Internally developed software | Minimum
Property, Plant and Equipment [Line Items]
Depreciable lives used for the principal depreciable asset classifications	3 years
Internally developed software | Maximum
Property, Plant and Equipment [Line Items]
Depreciable lives used for the principal depreciable asset classifications	10 years
Aircraft | Minimum
Property, Plant and Equipment [Line Items]
Operating leases, term	3 years
Aircraft | Maximum
Property, Plant and Equipment [Line Items]
Operating leases, term	12 years
Spare engines | Minimum
Property, Plant and Equipment [Line Items]
Operating leases, term	7 years
Spare engines | Maximum
Property, Plant and Equipment [Line Items]
Operating leases, term	12 years
Major spare rotable parts, avionics, and assemblies
Property, Plant and Equipment [Line Items]
Residual value, percentage	10.00%