Property and Equipment - Summary of Company's Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,380,410	$ 1,377,260
Less accumulated depreciation and amortization	(477,925)	(430,495)
Property and equipment, net	902,485	946,765
Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,227,341	1,225,205
Facility & Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	67,784	64,316
Operating Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	30,832	29,913
Data Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	35,889	34,747
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,798	8,202
Medical Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,710	8,354
Other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,056	$ 6,523

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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