Business Segments and Geographic Areas (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Schedule of Accounts Receivable and Revenue by Major Customers by Reporting Segments

The customers, individually or considered as a group under common ownership, which accounted for greater than 10% of accounts receivable or 10% of operating revenues during the periods reflected were as follows:

	Accounts Receivable December 31,				Operating Revenues Years Ended December 31,
	2017		2016		2017		2016		2015
Oil and Gas segment:
Customer A	11	%	8	%	14	%	14	%	15	%
Customer B	5	%	8	%	9	%	10	%	11	%
Air Medical & Technical Services segments:
Customer C	10	%	13	%	0	%	5	%	9	%

Schedule of Profit or Loss and Assets of Each of Company's Reportable Segments

	Year Ended December 31,
	2017			2016			2015
	(Thousands of dollars)
Segment operating revenues
Oil and Gas	$	298,398		$	324,129		$	459,611
Air Medical	257,273			281,868			312,775
Technical Services	23,874			28,101			31,842
Total operating revenues	579,545			634,098			804,228
Segment direct expenses
Oil and Gas (1)	321,272			344,640			411,757
Air Medical	208,987			227,877			246,487
Technical Services	16,825			19,882			29,112
Total segment direct expenses	547,084			592,399			687,356
Segment selling, general and administrative expenses
Oil and Gas	5,899			6,739			6,511
Air Medical	12,442			10,968			10,455
Technical Services	1,405			1,101			805
Total segment selling, general and administrative expenses	19,746			18,808			17,771
Total segment expenses	566,830			611,207			705,127
Net segment (loss) profit
Oil and Gas	(28,773		)	(27,250		)	41,343
Air Medical	35,844			43,023			55,833
Technical Services	5,644			7,118			1,925
Total net segment profit	12,715			22,891			99,101
Other, net (2)	2,098			6,214			1,872
Unallocated selling, general and administrative expenses	(34,071		)	(25,610		)	(28,651		)
Interest expense	(32,183		)	(30,644		)	(29,066		)
(Loss) earnings before income taxes	$	(51,441	)	$	(27,149	)	$	43,256

⁽¹⁾  Includes equity in gain/loss of unconsolidated affiliate.

⁽²⁾  Includes gain/loss on disposition of property and equipment, asset impairments, and other income.

Summary of Gains on Disposition of Property and Equipment and Other Income

	Year Ended December 31,
	2017		2016		2015
	(Thousands of dollars)
Expenditures for Long-Lived Assets
Oil and Gas	$	52,525	$	59,278	$	32,501
Air Medical	5,696		22,429		22,685
Corporate	257		1,164		1,389
Total	$	58,478	$	82,871	$	56,575

	As of or for Year Ended December 31,
	2017		2016		2015
	(Thousands of dollars)
Depreciation and Amortization
Oil and Gas	39,655		40,170		42,709
Air Medical	$	20,413	$	19,716	$	18,177
Technical Services	581		564		518
Corporate	7,378		5,293		10,214
Total	68,027		65,743		71,618
Assets
Oil and Gas	$	722,734	$	674,788
Air Medical	372,646		368,474
Technical Services	5,979		9,568
Corporate	300,487		395,610
Total	1,401,846		1,448,440

Summary of Company's Revenues from External Customers and Long-Lived Assets, by Geographical Areas

The following table presents the Company’s revenues from external customers attributed to operations in the United States and foreign areas and long-lived assets in the United States and foreign areas.

	As of or for Year Ended December 31,
	2017		2016		2015
	(Thousands of dollars)
Operating Revenues:
United States	$	530,115	$	579,300	$	722,339
International	49,430		54,798		81,889
Total	$	579,545	$	634,098	$	804,228
Long-Lived Assets:
United States	$	601,530	$	751,290
International	345,235		152,687
Total	$	946,765	$	903,977