Other Assets (Tables)

12 Months Ended

Dec. 31, 2017

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Company's Other Assets

The following table summarizes the Company’s other assets at December 31 of the following years:

	2017		2016
	(Thousands of dollars)
Deposits on future purchases of aircraft	$	501	$	4,818
Investment in Variable Interest Entities	330		1,351
Investments (Officers’ Deferred Compensation Plan)	2,685		2,394
Other	5,225		1,196
Total	$	8,741	$	9,759