Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Summary of Company's Property and Equipment

The following table summarizes the Company’s property and equipment at December 31 of the following years:

	2017			2016
	(Thousands of dollars)
Flight equipment	$	1,225,205		$	1,144,315
Facility & improvements	64,316			61,187
Operating equipment	29,913			25,966
Data processing equipment	34,747			33,881
Vehicles	8,202			8,567
Medical equipment	8,354			7,963
Other	6,523			5,667
	1,377,260			1,287,546
Less accumulated depreciation and amortization	(430,495		)	(383,569		)
Property and equipment, net	$	946,765		$	903,977