PHI (PHIG) 10-K 23 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 19, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	PHII
Entity Registrant Name	PHI INC
Entity Central Index Key	350,403
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 154,476,608
Voting Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		2,905,757
Non-Voting Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		12,897,614

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash	$ 8,770,000	$ 2,596,000
Short-term investments	64,237,000	289,806,000
Accounts receivable – net
Trade	168,153,000	128,662,000
Other	17,826,000	9,603,000
Inventories of spare parts – net	80,881,000	70,402,000
Prepaid expenses	11,475,000	9,259,000
Deferred income taxes	0	10,798,000
Income taxes receivable	1,271,000	540,000
Total current assets	352,613,000	521,666,000
Property and equipment – net	946,765,000	903,977,000
Restricted cash and investments	12,396,000	13,038,000
Other assets	8,741,000	9,759,000
Deferred income taxes	3,309,000	0
Goodwill	61,299,000	0
Intangibles	16,723,000	0
Total assets	1,401,846,000	1,448,440,000
Current Liabilities:
Accounts payable	37,186,000	28,704,000
Accrued and other current liabilities	41,850,000	28,346,000
Total current liabilities	79,036,000	57,050,000
Long-term debt:
Revolving credit facility	117,500,000	134,000,000
Senior Notes issued March 17, 2014, net of unamortized debt issuance costs of $1,506 and $2,753, respectively	498,494,000	497,247,000
Deferred income taxes	86,005,000	151,713,000
Other long-term liabilities	8,157,000	8,652,000
Commitments and contingencies (Note 13)
Shareholders’ Equity:
Additional paid-in capital	308,353,000	304,246,000
Accumulated other comprehensive loss	(280,000)	(478,000)
Retained earnings	303,001,000	294,441,000
Total shareholders’ equity	612,654,000	599,778,000
Total liabilities and shareholders’ equity	1,401,846,000	1,448,440,000
Voting Common Stock [Member]
Shareholders’ Equity:
Common stock	291,000	291,000
Non-Voting Common Stock [Member]
Shareholders’ Equity:
Common stock	1,289,000	1,278,000
Total shareholders’ equity	$ 1,289,000	$ 1,278,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt issuance costs	$ 1,506	$ 2,753
Voting Common Stock [Member]
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	12,500,000	12,500,000
Common stock, shares issued	2,905,757	2,905,757
Common stock, shares outstanding	2,905,757	2,905,757
Non-Voting Common Stock [Member]
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	37,500,000	37,500,000
Common stock, shares issued	12,897,614	12,779,646
Common stock, shares outstanding	12,897,614	12,779,646

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Operating revenues, net	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
Expenses:
Direct expenses									546,699	592,550	687,050
Selling, general and administrative expenses									53,817	44,418	46,422
Total operating expenses									600,516	636,968	733,472
Loss (gain) on disposition of assets, net	(287)	(4)	(7)	0	504	85	(4,298)	359	298	(3,350)	339
Impairments of assets									368	407	0
Equity in loss (profit) of unconsolidated affiliate									385	(151)	306
Operating income									(22,022)	224	70,111
Interest expense									32,183	30,644	29,066
Other income, net									(2,764)	(3,271)	(2,211)
Total expenses									29,419	27,373	26,855
(Loss) earnings before income taxes	(20,319)	(4,899)	(3,150)	(23,073)	(12,012)	(7,766)	117	(7,488)	(51,441)	(27,149)	43,256
Income tax (benefit) expense									(58,973)	(469)	16,332
Net earnings (loss)	$ 29,330	$ (3,277)	$ (3,273)	$ (15,248)	$ (17,058)	$ (4,967)	$ 4,277	$ (8,932)	$ 7,532	$ (26,680)	$ 26,924
Earnings (loss) per share:
Basic (USD per share)	$ 1.87	$ (0.21)	$ (0.21)	$ (0.97)	$ (1.08)	$ (0.32)	$ 0.27	$ (0.57)	$ 0.48	$ (1.70)	$ 1.73
Diluted (USD per share)	$ 1.87	$ (0.21)	$ (0.21)	$ (0.97)	$ (1.08)	$ (0.32)	$ 0.27	$ (0.57)	$ 0.48	$ (1.70)	$ 1.72
Weighted average shares outstanding:
Basic (shares)									15,762	15,663	15,566
Diluted (shares)									15,762	15,663	15,642

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings (loss)	$ 29,330	$ (3,277)	$ (3,273)	$ (15,248)	$ (17,058)	$ (4,967)	$ 4,277	$ (8,932)	$ 7,532	$ (26,680)	$ 26,924
Net unrealized gain (loss) on short-term investments									310	241	(641)
Other unrealized gain									0	0	24
Changes in pension plan assets and benefit obligations									(3)	(39)	7
Tax effect of the above-listed adjustments									(109)	(113)	254
Total comprehensive income (loss)									$ 7,730	$ (26,591)	$ 26,568

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Non-Voting Common Stock [Member]	Voting Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2014	$ 597,068	$ 1,258	$ 291	$ 301,533	$ (211)	$ 294,197
Balance, Shares at Dec. 31, 2014		12,576	2,906
Net earnings (loss)	26,924					26,924
Unrealized loss on short-term investments	(384)				(384)
Changes in pension plan assets and benefit obligations	4				4
Amortization of unearned stock-based compensation	5,799			5,799
Issuance of non-voting common stock (upon vesting of restricted stock units)	18	$ 18
Issuance of non-voting common stock (upon vesting of restricted stock units), shares		179
Cancellation of restricted non-voting stock units for tax withholdings on vested shares	(2,203)	$ (7)		(2,196)
Cancellation of restricted non-voting stock units for tax withholdings on vested shares, shares		(70)
Purchase and retirement of treasury stock	(252)			(252)
Other	24				24
Balance at Dec. 31, 2015	626,998	$ 1,269	$ 291	304,884	(567)	321,121
Balance, Shares at Dec. 31, 2015		12,685	2,906
Net earnings (loss)	(26,680)					(26,680)
Unrealized loss on short-term investments	113				113
Changes in pension plan assets and benefit obligations	(24)				(24)
Amortization of unearned stock-based compensation	4,819			4,819
Issuance of non-voting common stock (upon vesting of restricted stock units)	12	$ 12
Issuance of non-voting common stock (upon vesting of restricted stock units), shares		130
Cancellation of restricted non-voting stock units for tax withholdings on vested shares	(531)	$ (3)		(528)
Cancellation of restricted non-voting stock units for tax withholdings on vested shares, shares		(28)
Purchase and retirement of treasury stock	(4,929)			(4,929)
Other	0
Other, shares		(8)
Balance at Dec. 31, 2016	599,778	$ 1,278	$ 291	304,246	(478)	294,441
Balance, Shares at Dec. 31, 2016		12,779	2,906
Net earnings (loss)	7,532					7,532
Unrealized loss on short-term investments	200				200
Changes in pension plan assets and benefit obligations	(2)				(2)
Amortization of unearned stock-based compensation	4,374			4,374
Cumulative effect adjustment of unrecognized tax benefits	1,028					1,028
Issuance of non-voting common stock (upon vesting of restricted stock units)	0	$ 11		(11)
Issuance of non-voting common stock (upon vesting of restricted stock units), shares		140
Cancellation of restricted non-voting stock units for tax withholdings on vested shares	(256)			(256)
Cancellation of restricted non-voting stock units for tax withholdings on vested shares, shares		(22)
Balance at Dec. 31, 2017	$ 612,654	$ 1,289	$ 291	$ 308,353	$ (280)	$ 303,001
Balance, Shares at Dec. 31, 2017		12,897	2,906

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net earnings (loss)	$ 7,532		$ (26,680)	$ 26,924
Adjustments to reconcile net earnings to net cash (used in) provided by operating activities:
Depreciation and amortization	68,027		65,743	71,618
Deferred income taxes	(59,272)		(2,424)	12,894
Gain (loss) on asset dispositions	298		(3,350)	339
Equity in loss (income) of unconsolidated affiliate	385		(151)	306
Impairment of assets	368		407	0
Inventory valuation reserves	2,410		5,179	3,231
Other	0		0	(1,277)
Changes in operating assets and liabilities:
Accounts receivable	(28,329)	[1]	(351)	36,579
Inventories of spare parts	(6,793)	[1]	(5,064)	1,441
Income taxes receivable	186	[1]	220	466
Other assets	(9,050)	[1]	(14,837)	(14,998)
Accounts payable and accrued liabilities	5,754	[1]	(19,111)	(3,859)
Other long-term liabilities	(619)	[1]	(142)	254
Net cash (used in) provided by operating activities	(19,103)	[1]	(564)	133,918
Investing activities:
Purchase of property and equipment	(56,757)		(81,842)	(57,123)
Proceeds from asset dispositions	1,296		14,983	5,236
Purchase of short-term investments	(637,980)		(321,453)	(608,649)
Proceeds from sale of short-term investments	862,942		316,543	505,966
Payments of deposits on aircraft	0		(2,249)	(1,273)
Refunds of deposits on aircraft	0		0	6,010
Loan to unconsolidated affiliate	0		(1,200)	0
Loan to third party	(824)		0	0
Business acquisitions net of cash acquired	(126,644)		0	0
Net cash provided by (used in) investing activities	42,033		(75,218)	(149,833)
Financing activities:
Repurchase of common stock	(256)		(529)	(2,448)
Proceeds from line of credit	152,150		264,700	232,660
Payments on line of credit	(168,650)		(188,200)	(218,160)
Net cash provided by financing activities	(16,756)		75,971	12,052
Increase (decrease) in cash	6,174		189	(3,863)
Cash, beginning of year	2,596		2,407	6,270
Cash, end of year	8,770		2,596	2,407
Cash paid during the period for:
Interest	30,517		29,169	27,657
Income Taxes	1,231		2,637	5,521
Accrued payables related to purchases of property and equipment	$ 42		$ 29	$ 1,339
[1]	Net of the effect of business acquisitions.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations, Basis of Consolidation, and Other General Principles PHI, Inc. and its subsidiaries (“PHI,” the “Company,” “we,” “us,” or “our”) provide transportation services to, from, and among offshore facilities for customers engaged in the oil and gas exploration, development, and production industry. We provide these offshore services primarily in the United States and to a lesser extent in Canada, Trinidad, Australia, New Zealand, Papua New Guinea, the Philippines, West Africa and the Middle East. We also provide air medical transportation services for hospitals and emergency service agencies, as well as aircraft maintenance and repair services to third parties in North America. The consolidated financial statements include the accounts of PHI, Inc. and its subsidiaries after the elimination of all intercompany accounts and transactions. We apply the equity method of accounting for investments in entities, if we have the ability to exercise significant influence over the operating and financial policies of the entity. We report our share of earnings or losses of equity investees in the accompanying Consolidated Statements of Operations as equity in (loss) profit of unconsolidated affiliate. At December 31, 2017 , Al A. Gonsoulin, Chairman of the Board and Chief Executive Officer, beneficially owned stock representing approximately 70.9% of the total voting power. As a result, he exercises control over the election of PHI’s directors and the outcome of matters requiring a shareholder vote. Use of Estimates The preparation of financial statements is in conformity with accounting principles generally accepted in the United States of America (“GAAP”), which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from those estimates. Significant estimates include: Estimates of contractual allowances applicable to billings in the Air Medical segment, Inventories of spare parts, Valuation reserve related to obsolete and excess inventory, Reserves related to unpaid accounts, Depreciable lives and salvage values of property and equipment, Valuation allowance for deferred tax assets, Fair values of assets acquired and liabilities assumed, Income taxes, Healthcare insurance claims and workers’ compensation liability, and Impairment of long-lived assets. Cash and Cash Equivalents We consider all highly liquid investments with maturities of three months or less , when purchased, to be cash equivalents. Trade Receivables, net Trade and other receivables are stated at net realizable value. Air Medical trade receivables are presented net of allowances for contractual discounts and uncompensated care. We estimate contractual allowances and uncompensated care based on historical collection experience by payor category. The main payor categories are Medicare, Medicaid, private insurance, and self-pay. We analyze our historical payment of accounts by payor category on a monthly basis, and adjust our accounts receivable allowance based upon each category’s historical collection percentage plus any adjustments for current trends in payor behavior. Provisions for contractual discounts and uncompensated care that we applied to our Air Medical trade receivables (expressed as a percentage of total segment accounts receivable) at December 31 were as follows: 2017 2016 Allowance for contractual discounts 53% 56% Allowance for uncompensated care 24% 23% Short-term Investments Short-term investments consist of money market funds, commercial paper, debt issued by the U.S. government or its agencies, and corporate bonds and notes, which represent funds available for current operations. In accordance with GAAP, these short-term investments are classified as available for sale. We recorded $0.3 million in net unrealized losses in 2017. These losses are reflected as a separate component of stockholders’ equity. Inventories of Spare Parts The Company’s inventories are stated at average cost and consist primarily of spare aircraft parts. Portions of the Company’s inventories are used parts that are often exchanged with parts removed from aircraft, reworked to a useable condition according to manufacturers’ and FAA specifications, and returned to inventory. Reusable aircraft parts are included in inventory at the average cost of comparable parts. The rework costs are expensed as incurred. The Company also records an allowance for obsolete and slow-moving parts, relying principally on specific identification of such inventory. Valuation reserves related to obsolescence and slow-moving inventory were $20.9 million and $17.3 million at December 31, 2017 and 2016 , respectively. Property and Equipment The Company records its property and equipment at cost less accumulated depreciation. For financial reporting purposes, the Company uses the straight-line method to compute depreciation based upon estimated useful lives of 5 to 15 years for flight equipment and 3 to 10 years for other equipment. Leasehold improvements are amortized over the shorter of the life of the respective asset or the term of the lease agreement and range from 6 to 10 years. The salvage value used in calculating depreciation of aircraft ranges from 25% to 54% of the aircraft’s carrying value, based upon historical aircraft sales data (historical as of 2007). The cost of scheduled inspections and modifications for flight equipment are charged to maintenance expense as incurred. We charge maintenance and repair costs to earnings as the costs are incurred. The cost of certain aircraft components are covered under contractual arrangements with the applicable aircraft manufacturer, commonly referred to as “power-by-the-hour” contracts. Under these agreements, we are charged an agreed amount per hour of flying time. The costs charged under these contractual arrangements are recognized in the period in which the flight hours occur. To the extent that we have not yet been billed for costs incurred under these arrangements, these costs are included in accrued expenses on our consolidated balance sheets. Modifications that enhance the operating performance or extend the useful lives of the aircraft are capitalized and depreciated over the remaining life of the aircraft. Upon selling or otherwise disposing of property and equipment, the Company removes the cost and accumulated depreciation from the accounts and reflects any resulting gain or loss in earnings at the time of sale or other disposition. The Company reviews its long-lived tangible assets for impairment annually, or more frequently if events or a change of circumstances indicate that an impairment may have occurred. The Company reviews certain identifiable intangibles for impairment whenever events or changes in circumstances indicate that the carrying amount of any such asset may not be recoverable. In such evaluation, the estimated future undiscounted cash flows generated by a particular asset group are compared with the book value of the asset group to determine if an impairment charge is necessary. Similar aircraft model types are grouped together for impairment testing purposes. The Company measures recoverability of assets to be held and used by comparing the carrying amount of an asset to future undiscounted net cash flows that it expects the asset to generate. When the Company determines that an asset is impaired, the Company recognizes that impairment amount, which is measured by the amount that the carrying value of the asset exceeds its fair value. In addition to the periodic review of its active long-lived tangible assets for impairment when circumstances warrant, the Company also performs a review of its parked aircraft not expected to return to service annually or whenever changes in circumstances indicate the carrying amount of an aircraft may not be recoverable. Management estimates the fair value of each aircraft not expected to return to service by considering items such as the aircraft’s age, length of time parked, likelihood of return to active service, and actual recent sales of similar aircraft. For more significant aircraft carrying values, we obtain an estimate of the fair value of the parked aircraft form third-party appraisers for use in our determination of fair value estimates. The Company records an impairment charge when the carrying value of a parked aircraft not expected to return to active service exceeds its estimated fair market value. During the twelve months ended December 31, 2017 , we sold or disposed of six medium, one fixed wing aircraft and related parts inventory utilized in our Oil and Gas segment. Cash proceeds totaled $1.3 million , resulting in a loss of $0.3 million . These aircraft no longer met our strategic needs. During the twelve months ended December 31, 2016 , we sold twelve light, eleven medium aircraft, and related parts inventory previously utilized in our Oil and Gas segment. Cash proceeds totaled $ 15.0 million , resulting in a gain of $ 3.3 million . These aircraft no longer met our strategic needs. During the twelve months ended December 31, 2015, we sold eight light and six medium aircraft previously utilized in our Oil and Gas segment. The carrying value of these assets prior to the sale was $3.7 million . These assets were sold for $3.7 million , which resulted in no gain. These aircraft no longer met our strategic needs. We also sold the associated spare parts inventory for these aircraft, which resulted in a $0.3 million loss. Impairment Losses In connection with our normal recurring impairment testing, we recorded an impairment loss in the year ended December 31, 2017 for two light aircraft in our Oil and Gas segment. The carrying value of these aircraft was $1.8 million . Following a market analysis, we determined that the market value for these aircraft is $1.4 million (based on a Level 3 review, as defined by ASC 820, Fair Value Measurements and Disclosures). As a result of this analysis, we recorded an aggregate non-cash pre-tax impairment loss of $0.4 million for 2017 . We had $0.4 million impairment losses in the year ended December 31, 2016 . We had no impairment losses for the year ended December 31, 2015 . Fair Value of Assets and Liabilities Acquired and Identification of Associated Goodwill and Intangible Assets In conjunction with each acquisition we make, we must allocate the cost of the acquired entity to the assets and liabilities assumed based on their estimated fair values at the date of acquisition. As additional information becomes available, we may adjust the original estimates within a short time period subsequent to the acquisition. In addition, we are required to recognize intangible assets separately from goodwill. Determining the fair value of assets and liabilities acquired, as well as intangible assets that relate to such items as customer relationships, contracts, trade names and non-compete agreements involves professional judgment and is ultimately based on acquisition models and management’s assessment of the value of the assets acquired, and to the extent available, third party assessments. Intangible assets with finite lives are amortized over their estimated useful life as determined by management. Whenever events or changes in circumstances indicate that the carrying amount of the intangible assets may not be recoverable, the intangible assets will be reviewed for impairment. Goodwill is not amortized but instead is periodically assessed for impairment. Uncertainties associated with these estimates include fluctuations in economic obsolescence factors in the area and potential future sources of cash flow. We cannot provide assurance that actual amounts will not vary significantly from estimated amounts. Additionally, we recorded the estimated fair value of net assets acquired and liabilities assumed in connection with our acquisition of HNZ Offshore Business as of the acquisition date of December 29, 2017. The fair value measurements were primarily based on significant unobservable inputs (Level 3 as defined in Note 4) developed using company-specific information and third-party appraisals for the aircraft. See Note 2 for further information associated with the values recorded in our acquisition. Goodwill Goodwill represents the amount the purchase price exceeds the fair value of net assets acquired in a business combination. Goodwill has an indefinite useful life and is not amortized, but is assessed for impairment annually or when events or changes in circumstances indicate that a potential impairment exists. Based on our assessments of the fair values of the assets we acquired and liabilities we assumed in connection with our acquisition of the HNZ Offshore Business on December 29, 2017 (discussed further in Note 2), we recognized goodwill in the fourth quarter. The following table summarizes recent activity regarding the Company's goodwill (in thousands): Oil & Gas Air Medical Technical Services Total Balance December 31, 2016 — — — — Acquisition Activities 61,299 — — 61,299 Balance December 31, 2017 61,299 — — 61,299 Other Intangible Assets In connection with our acquisition of the HNZ Offshore Business, we also recognized in the fourth quarter of 2017 intangible assets for customer relationship, non-compete and tradenames. Intangible assets with finite useful lives are amortized over estimated useful lives on a straight-line basis. Our intangible assets by types consist of the following (in thousands): Estimated Useful Lives Gross Amount Accumulated Amortization Net Balance Customer Relationship 15 11,622 — 11,622 Non-Compete Agreements 5 900 — 900 Tradenames 7 4,201 — 4,201 Total 16,723 — 16,723 Based on the carrying values of our intangible assets at December 31, 2017, amortization expense for the next five years (2018 through 2022) is estimated to be $1.6 million per year. Deferred Financing Costs Costs incurred to obtain long-term debt financing are deferred and amortized ratably over the term of the related debt agreement. Self-Insurance The Company maintains a self-insurance program for a portion of its healthcare costs. Self-insurance costs are accrued based upon the aggregate of the liability for reported claims and the estimated liability for claims incurred but not reported. The Company’s insurance retention was $250,000 per claim through December 31, 2017 . As of December 31, 2017 and 2016 , the Company had $1.3 million and $1.9 million , respectively, of accrued liabilities related to healthcare claims. There is also a $0.5 million deductible per incident on our workers’ compensation program. We have accrued $2.9 million and $2.5 million for the years 2017 and 2016 , respectively, related to workers’ compensation claims. The Company owns an offshore insurance company to realize savings in reinsurance costs on its insurance premiums. We paid $0.5 million and $0.6 million , respectively, to this captive company in 2017 and 2016 , which were eliminated in consolidation. The results of the captive are fully consolidated in the accompanying consolidated financial statements. Revenue Recognition The Company recognizes revenue related to aviation transportation services after the services are performed or the contractual obligations are met. Aircraft maintenance services revenues are recognized at the time the repair or services work is completed. Revenues related to the Company’s Air Medical segment independent provider model services are recorded net of contractual allowances under agreements with third party payors, and also recorded net of uncompensated care allowances when the services are provided. Revenues generated under the traditional provider model consist of a fixed monthly rate for aircraft availability and an hourly rate for flight time. We estimate contractual allowances and uncompensated care based on historical collection experience by payor category. The main payor categories are Medicaid, Medicare, private insurance, and self-pay. Changes in payor mix, reimbursement rates and uncompensated care rates are the factors most subject to sensitivity and variability in calculating our allowances. We compute a historical payment analysis of accounts by category. The allowance percentages calculated are applied to the payor categories, and the necessary adjustments are made to the revenue allowance. In our Air Medical Segment, the allowance for contractual discounts against outstanding accounts receivable was $117.8 million , $111.9 million , and $103.6 million as of December 31, 2017 , 2016 , and 2015 , respectively, and the allowance for uncompensated care against outstanding accounts receivable was $52.5 million , $46.3 million , and $41.9 million as of December 31, 2017 , 2016 , and 2015 , respectively. Included in the allowance for uncompensated care above is the value of services to patients who are unable to pay when it is determined that they qualify as charity care. The value of these services was $7.1 million , $8.8 million , and $9.3 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The estimated cost of providing charity services was $1.6 million , $1.9 million , and $2.0 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The estimated costs of providing charity services are based on a calculation that applies a ratio of costs to the charges for uncompensated charity care. The ratio of costs to charges is based on the Air Medical independent provider model’s total expenses divided by gross patient service revenue. In determining the allowance estimates for our Air Medical segment’s billing, receivables and revenue, we utilize the prior twelve months’ payment history and current trends in payor behavior by each separate payor group, which we evaluate on a state by state basis. A percentage of amounts collected compared to the total invoice is determined from this process and applied to the current month’s billings and receivables. If a receivable related to the self-pay category is outstanding twelve months or greater, we record a reserve equal to 100% of the receivable. Receivables related to other payor categories are scrutinized when they are outstanding for nine months or longer and additional allowances are recorded if warranted. Provisions for contractual discounts and estimated uncompensated care that we applied to our Air Medical revenues (expressed as a percentage of total independent provider model billings) were as follows: Year Ended December 31, 2017 2016 2015 Provision for contractual discounts 66 % 67 % 65 % Provision for uncompensated care 7 % 6 % 8 % Amounts attributable to Medicaid, Medicare, private insurance, and self-pay as a percentage of net Air Medical independent provider model revenues were as follows: Year Ended December 31, 2017 2016 2015 Insurance 72 % 72 % 74 % Medicare 18 % 18 % 17 % Medicaid 9 % 9 % 8 % Self-Pay 1 % 1 % 1 % Under a contract that commenced on September 29, 2012, our Air Medical affiliate provided multiple products and services to a customer in the Middle East, including helicopter leasing, emergency medical helicopter flight services, aircraft maintenance, provision of spare parts and insurance coverage for the customer-owned aircraft, training services, and base construction. The initial contract expired in late September 2015 and was extended through September 30, 2016, when it lapsed. Each of the major deliverables mentioned above qualify as separate units of accounting under the accounting guidance for such arrangements. The selling price for each service was determined based upon third-party evidence and estimates. Income Taxes Income taxes are accounted for in accordance with the provisions of Accounting Standards Codification 740, Income Taxes . The Company provides for income taxes using the asset and liability method under which deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. The deferred tax assets and liabilities measurement uses enacted tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company recognizes the effect of any tax rate changes in income of the period that includes the enactment date. In connection with recording deferred income tax assets and liabilities, the Company establishes valuation allowances when necessary to reduce deferred income tax assets to amounts that it believes are more likely than not to be realized. The Company evaluates its deferred tax assets quarterly to determine whether positive or negative adjustments to its valuation allowances are appropriate in light of changes in facts or circumstances, such as changes in tax law or interactions with taxing authorities. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion of the deferred tax assets will not be realized. Adjustments to the amount of our valuation allowances can materially impact our financial condition and results of operations. The Tax Cuts and Jobs Act (the "Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35% to 21%. Following the enactment of Tax Reform Legislation in December 2017, the SEC staff issued Staff Accounting Bulletin 118 - "Income Tax Accounting Implications of the Tax Cuts and Jobs Act" (SAB 118), which provides for a measurement period of up to one year from the enactment date to complete accounting under GAAP for the tax effects of the legislation. As of December 31, 2017, the Company has not completed its accounting for the tax effects of the Act. However, the Company has remeasured its net deferred tax liability at December 31, 2017 and has provisionally recognized a net benefit of $49.2 million in its consolidated statement of operations for the year ended December 31, 2017. The Company is still analyzing certain aspects of the Act and refining its calculations, which could potentially affect the measurement of these balances or potentially give rise to changes to its current provisional estimates. The Company’s estimates may be affected by a wide variety of factors, including additional regulatory guidance issued with respect to the Act. Any adjustments to the provisional amounts will be recognized as a component of income tax in the period in which the adjustments are determined. The Act also includes provisions to tax a new class of income called Global Intangible Low-Taxed Income (“GILTI”). Because of the complexity of the new GILTI tax rules, the Company is continuing to evaluate this provision of the Act and the application of existing income tax accounting guidance. Under GAAP, the Company is allowed to make an accounting policy choice of either (i) treating taxes due on future U.S. inclusions in taxable income related to GILTI as a current period expense when incurred or (ii) factoring such amounts into the measurement of deferred taxes. The Company has not adopted an accounting policy for the GILTI policy election as of December 31, 2017. The Company will evaluate its alternatives related to accounting policies for GILTI and adopt an accounting policy in 2018. Earnings per Share Basic earnings per share is computed by dividing earnings (loss) during the period by the weighted average number of voting and non-voting shares outstanding during each period. Diluted earnings per share is computed by dividing net income (loss) during the period by the weighted average number of shares of common stock that would have been outstanding assuming the issuance of potentially dilutive shares of common stock, as if such shares were outstanding during the reporting period, net of shares to be repurchased using the treasury stock method. Dilutive shares for this purpose assumes restricted stock unit awards have vested. Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of trade accounts receivables. Approximately 10.7% of our trade accounts receivables at December 31, 2017 were owed by an overseas customer. For a variety of reasons, the Company believes it will be paid all or substantially all of the amounts due under these receivables. Accordingly, the Company does not believe that it had significant credit risk at December 31, 2017 with respect to these overseas trade accounts receivable specifically or its aggregate trade accounts receivable generally. PHI conducts a majority of its business with major and independent oil and gas exploration and production companies with operations in the Gulf of Mexico. The Company also provides services to major medical centers. The Company continually evaluates the financial strength of its customers, but generally does not require collateral to secure its customer receivables. The Company establishes an allowance for doubtful accounts based upon factors pertaining to the credit risk of specific customers, current market conditions, and other information. Amounts are charged off as uncollectible when collection efforts have been exhausted. The allowance for doubtful accounts was $7.2 million and $6.0 million at December 31, 2017 and 2016 , respectively. Trade receivables representing amounts due pursuant to air medical independent provider model services are carried net of an allowance for estimated contractual adjustments and uncompensated care on unsettled invoices. The Company monitors its collection experience by payor category within the Air Medical segment and updates its estimated collections to be realized as deemed necessary. In our Air Medical segments, the allowance for contractual discounts was $117.8 million , $111.9 million , and $103.6 million as of December 31, 2017 , 2016 , and 2015 , respectively, and the allowance for uncompensated care was $52.5 million , $46.3 million , and $41.9 million as of December 31, 2017 , 2016 , and 2015 , respectively. The Company’s two largest oil and gas customers accounted for 23% of consolidated operating revenues for the year ended December 31, 2017 , 24% for the year ended December 31, 2016 , and 26% for the year ended December 31, 2015 . The Company also carried accounts receivable from these same customers totaling 16% and 16% of net trade receivables on December 31, 2017 and 2016 , respectively. The customer base of our Air Medical and Technical Services operations has traditionally been less concentrated than the customer base of our Oil and Gas operations. Over the past three years, none of our current Air Medical or Technical Services customers accounted for more than 2% of our consolidated operating revenues. One of our former Air Medical customers, however, did account for 5% and 9% of our consolidated operating revenues for 2016 and 2015, respectively. The Company also carried accounts receivable from its largest customer totaling 10% and 13% of net trade receivables on December 31, 2017 and 2016 , respectively. Substantially all of the Company’s cash is maintained in one financial institution in amounts that typically exceed federally insured limits. The Company has not experienced any losses in such accounts and based on current circumstances does not believe that it is exposed to significant credit risk. Foreign Currency Translation Our consolidated financial statements are reported in U.S. dollars. Our foreign subsidiaries maintain their records primarily in the currency of the country in which they operate. Assets and liabilities of foreign subsidiaries in non-highly inflationary economies are translated into U.S. dollars using rates of exchange at the balance sheet date. Translation adjustments are recorded in other comprehensive income (loss). Revenues and expenses are translated at rates of exchange in effect during the year. Transaction gains and losses are recorded in net earnings (loss). New Accounting Pronouncements On January 26, 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350) : Simplifying the Test for Goodwill Impairment (ASU 2017-04). ASU 2017-04 removes the requirement to compare the implied fair value of goodwill with the carrying amount as part of Step 2 of the goodwill impairment test. Under the new standard, the goodwill impairment loss will be measured as the excess of a reporting unit's carrying amount over its fair value, not exceeding the total amount of goodwill allocated to that reporting unit, which may increase the frequency of goodwill impairment charges if a future goodwill impairment test does not pass the Step 1 evaluation. ASU 2017-04 is effective prospectively for periods beginning on or after December 15, 2019, with early adoption permitted. The Company adopted ASU 2017-04 effective January 1, 2018. The Company will perform goodwill impairment test under the new standard in 2018. Effective January 1, 2017, we adopted Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718) : Improvements to Employee Share-Based Payment Accounting, which was issued by the Financial Accounting Standards Board (“FASB”) in March 2016. This new standard requires that excess tax benefits and deficiencies resulting from stock-based compensation awards vesting and exercises be recognized in the income statement. Previously, these amounts were recognized in additional paid-in capital. As a result, during the first quarter of 2017 we recorded a cumulative-effect adjustment of $1.0 million increasing retained earnings and decreasing deferred tax liability on our balance sheet dated December 31, 2017. Accordingly, we recorded income tax expense of $0.9 million in our consolidated statement of operations for the year ended December 31, 2017, in recognition of excess tax deficiencies related to equity compensation. Under this new standard, the corresponding cash flows are now reflected in cash provided by operating activities instead of financing activities, as was previously required. In 2014, the FASB issued ASC 606, Revenue from Contracts with Customers (ASC 606), replacing the existing accounting standard and industry specific guidance for revenue recognition with a five-step model for recognizing and measuring revenue from contracts with customers. The underlying principle of the new standard is to recognize revenue to depict the transfer of goods or services to customers at the amount expected to be collected. The new standard also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenue and the related cash flows arising from contracts with customers. The Company has completed the evaluation of all revenue streams and determined that the adoption of ASC 606 will not change the current timing of revenue recognition for such transactions. Entities can transition to the standard either retrospectively or as a cumulative effect adjustment as of the date of adoption. The new standard is effective for the Company beginning on January 1, 2018. We adopted this standard on January 1, 2018 utilizing the modified retrospective method. Under the modified retrospective method of adoption, prior year reported results are not recast; however, a cumulative-effect adjustment to retained earnings at January 1, 2018 is recorded. In addition, quarterly disclosures will include comparative information on 2018 financial statement line items under current guidance. To the extent applicable, upon adoption, we may be required to comply with expanded disclosure requirements, including the disaggregation of revenues to depict the nature and uncertainty of types of revenues, contract assets and liabilities, performance obligations, significant judgments and estimates affecting the amount and timing of revenue recognition, and determination of transaction prices. The adoption of ASC 606 did not result in a cumulative-effect adjustment. Revenues in our Oil and Gas segment and Air Medical segment hospital contracts are primarily comprised of a fixed monthly fee for a particular model of aircraft, plus a variable component based on flight time. Under the independent provider programs of our Air Medical segment, our revenues are based on a flat rate plus a variable charge per patient-loaded mil

Acquisition of Business

Acquisition of Business	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition of Business	ACQUISITION OF BUSINESS On December 29, 2017, we completed a series of transactions with HNZ Group, Inc. (“HNZ”) and 2075568 Alberta ULC, a company newly-formed by the former Chief Executive Officer of HNZ for purposes of purchasing the stock of HNZ (the “Canadian Purchaser”). On December 29, 2017, we provided term loans to the Canadian Purchaser in an aggregate principal amount of approximately CAD $167.5 million (equivalent to USD $131.6 million ) substantially all of which was repaid the same date in exchange for receipt of HNZ’s offshore helicopter services business conducted in New Zealand, Australia, the Philippines and Papua New Guinea (the “HNZ Offshore Business”). The remaining balance of USD $0.8 million is expected to be repaid on or prior to December 31, 2019, or at such other time as mutually-agreed between the Canadian Purchaser and us. We funded our term loans to the Canadian Purchaser on December 29, 2017 primarily with the proceeds of maturing or liquidated short-term investments. In the fourth quarter of 2017, we recognized the assets that we acquired and the liabilities that we assumed in connection with the HNZ Offshore Business at their estimated acquisition date fair values. See Note 1 for information on goodwill and other intangible assets that we recorded in connection with the acquisition. As of December 31, 2017, we had recognized approximately $2.3 million in cumulative merger-related transaction costs, including legal and advisory fees in the selling, general and administrative expenses section of the accompanying Consolidated Statements of Operations. The fair value of the acquired assets and liabilities noted in the table may change during the provisional period, which may last up to twelve months subsequent to the acquisition date. The Company may obtain additional information to refine the valuation of the acquired assets and liabilities and adjust the recorded fair value. Adjustments recorded to the acquired assets and liabilities will be applied prospectively. The following amounts represent the fair value of assets acquired and liabilities assumed in the merger. Thousands of dollars Cash $ 4,142 Accounts receivable 27,819 Inventories 3,096 Fixed assets 43,689 Intangible assets: Noncompete agreements (weighted-average life of 5 years) 900 Customer relationships (weighted-average life of 15 years) 11,622 Tradenames (weighted-average life of 7 years) 4,201 Other assets 5,310 Accounts payable and accrued liabilities (25,272 ) Deferred taxes (1) (5,270 ) Other liabilities (750 ) Total identifiable net assets 69,487 Goodwill (2) 61,299 Total consideration transferred $ 130,786 (1) In connection with the acquisition accounting, PHI provided deferred taxes related to the estimated fair value adjustments for acquired intangible assets. (2) Goodwill is the excess of purchase price over fair market value of the net assets acquired under the acquisition method of accounting. The amount of goodwill that is deductible for income tax purposes is not significant. We did not record earnings in December for the acquired business due to the immateriality of the earnings resulting after the acquisition from December 30th through the 31st. ASC 805, Business Combinations, requires the disclosure of additional information including the revenue and earnings of the combined entity as though the business combination that occurred during the current year had occurred at the beginning of the prior annual reporting period (supplemental pro forma information). The Company has determined that disclosure of such information was impractical and is not provided as the financial records of the acquiree were not adequate to allow the preparation of supplemental pro forma information.

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investments	INVESTMENTS We classify all of our short term investments as available-for-sale. We carry these at fair value and report unrealized gains and losses, net of taxes, in Accumulated other comprehensive (loss) income, which is a separate component of shareholders’ equity in our consolidated balance sheets, and in our consolidated statements of shareholders’ equity. Cost, gains, and losses are determined using the specific identification method. In the years ended December 31, 2017 , 2016 , and 2015 , we received proceeds from the sales of these securities of $862.9 million , $316.5 million , and $506.0 million , respectively. Gains and losses on these sales were negligible and all amounts reclassified from accumulated other comprehensive income were immaterial. Investments consisted of the following as of December 31, 2017 : Cost Basis Unrealized Gains Unrealized Losses Fair Value (Thousands of dollars) Investments: Money market mutual funds $ 5,601 $ — $ — $ 5,601 Commercial paper — — — — U.S. government agencies 7,501 — (34 ) 7,467 Corporate bonds and notes 63,880 — (330 ) 63,550 Subtotal 76,982 — (364 ) 76,618 Deferred compensation plan assets included in other assets 2,685 — — 2,685 Total $ 79,667 $ — $ (364 ) $ 79,303 $12.4 million of our investments at December 31, 2017 were long-term and included on the balance sheet as restricted investments as they are securing outstanding letters of credit with maturities beyond one year. As noted in Note 2, we liquidated a substantial portion of our short-term investments in connection with acquiring the HNZ Offshore Business on December 29, 2017. Investments consisted of the following as of December 31, 2016 : Cost Basis Unrealized Gains Unrealized Losses Fair Value (Thousands of dollars) Investments: Money market mutual funds $ 18,118 $ — $ — $ 18,118 Commercial paper 27,906 — (39 ) 27,867 U.S. government agencies 13,295 — (32 ) 13,263 Corporate bonds and notes 244,202 2 (622 ) 243,582 Subtotal 303,521 2 (693 ) 302,830 Deferred compensation plan assets included in other assets 2,394 — — 2,394 Total $ 305,915 $ 2 $ (693 ) $ 305,224 $13.0 million of our investments at December 31, 2016 were long-term and included on the balance sheet as Restricted investments as they are securing outstanding letters of credit with maturities beyond one year. The following table presents the cost and fair value of our debt investments based on maturities as of December 31, 2017 2016 Amortized Costs Fair Value Amortized Costs Fair Value (Thousands of dollars) Due in one year or less $ 31,348 $ 31,254 $ 184,587 $ 184,334 Due within two years 40,032 39,763 100,816 100,378 Total $ 71,380 $ 71,017 $ 285,403 $ 284,712 The following table presents the average coupon rate percentage and the average days to maturity of our debt investments as of December 31, 2017 2016 Average Coupon Rate (%) Average Days To Maturity Average Coupon Rate (%) Average Days To Maturity Commercial paper — 0 1.001 184 U.S. government agencies 1.370 370 0.970 400 Corporate bonds and notes 1.766 392 1.745 318 The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for less than twelve months as of December 31, 2017 2016 Fair Value Unrealized Losses Fair Value Unrealized Losses (Thousands of dollars) Commercial paper $ — $ — $ 27,867 $ (39 ) U.S. government agencies 5,472 (28 ) 13,263 (32 ) Corporate bonds and notes 44,069 (271 ) 210,836 (602 ) Total $ 49,541 $ (299 ) $ 251,966 $ (673 ) The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for twelve months or more as of December 31, 2017 2016 Fair Value Unrealized Losses Fair Value Unrealized Losses (Thousands of dollars) U.S. government agencies $ 1,994 $ (6 ) $ — $ — Corporate bonds and notes $ 19,482 $ (59 ) $ 24,196 $ (20 ) Total $ 21,476 $ (65 ) $ 24,196 $ (20 ) As noted above, from time to time over the periods covered in our financial statements included herein, our investments have experienced net unrealized losses. We consider these declines in market value to be due to market conditions, and we do not plan to sell these investments prior to maturity. For these reasons, we do not consider any of our investments to be other than temporarily impaired at December 31, 2017 and 2016 . The assessment of whether an investment in a debt security has suffered an other-than-temporary impairment is based on whether the Company has the intent to sell or more likely than not will be required to sell the debt security before recovery of its amortized costs. Further, if the Company does not expect to recover the entire amortized cost basis of the debt security, an other-than-temporary impairment is considered to have occurred and it is measured by the present value of cash flows expected to be collected less the amortized cost basis (credit loss). The Company determined it did not have any other-than-temporary impairments relating to credit losses on debt securities for the year ended December 31, 2017 or 2016 .

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value	FAIR VALUE Accounting guidance defines fair value as the price that would be received to sell an asset or transfer a liability in an orderly transaction between market participants at the measurement date. This guidance establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. The hierarchy for inputs is categorized into three levels based on the reliability of inputs as follows: Level 1: Quoted market prices in active markets for identical assets or liabilities. Level 2: Observable market based inputs or unobservable inputs that are corroborated by market data. Level 3: Unobservable inputs that are not corroborated by market data. The following tables summarize the valuation of our investments and financial instruments by the above pricing levels as of the valuation dates listed: December 31, 2017 Total (Level 1) (Level 2) (Thousands of dollars) Investments: Money market mutual funds $ 5,601 $ 5,601 $ — Commercial paper — — — U.S. government agencies 7,467 — 7,467 Corporate bonds and notes 63,550 — 63,550 76,618 5,601 71,017 Deferred compensation plan assets 2,685 2,685 Total $ 79,303 $ 8,286 $ 71,017 December 31, 2016 Total (Level 1) (Level 2) (Thousands of dollars) Investments: Money market mutual funds $ 18,118 $ 18,118 $ — Commercial paper 27,867 — 27,867 U.S. government agencies 13,263 — 13,263 Corporate bonds and notes 243,582 — 243,582 302,830 18,118 284,712 Deferred compensation plan assets 2,394 2,394 — Total $ 305,224 $ 20,512 $ 284,712 The Company holds its short-term investments in an investment fund consisting of high quality money market instruments of governmental and private issuers, which is classified as a short-term investment. Level 1 inputs are quoted prices (unadjusted) for identical assets or liabilities in active markets. These items are traded with sufficient frequency and volume to provide pricing on an ongoing basis. The fair values of the shares of these funds are based on observable market prices, and therefore, have been categorized in Level 1 in the fair value hierarchy. Level 2 inputs reflect quoted prices for identical assets or liabilities that are not active. These items may not be traded daily; examples include corporate bonds and U.S. government agencies. Assets are valued based on prices derived by independent third parties that use inputs such as benchmark yields, reported trades, broker/dealer quotes, and issuer spreads. Management reviews these prices and reserves the right to override them if, based on additional information, management believes such changes would be more reflective of fair value. Investments included in other assets, which relate to the liability for the Officers’ Deferred Compensation Plan, consist mainly of multiple investment funds that are highly liquid and diversified. Cash, accounts receivable, accounts payable and accrued liabilities all had fair values approximating their carrying amounts at December 31, 2017 and 2016 . The carrying value of our variable-rate indebtedness under our revolving credit facility approximates its fair value as of December 31, 2017 . The fair value of our 5.25% Senior Notes was $499.2 million at December 31, 2017. In connection with its impairment testing (discussed further in Note 1), the Company estimates cash flows and asset appraisals based upon historical data adjusted for the Company’s best estimate of expected future market performance. If an asset group fails the undiscounted cash flow test or appraisal value, the Company compares the market value to the book value of each asset group in order to determine if impairment exists (considered Level 3, as defined by ASC 820, Fair Value Measurements and Disclosures). If impairment exists, the book value of the asset group is reduced to its estimated fair value. The below table summarizes the combined fair value of the assets that incurred impairments during the years ended December 31, 2017 , 2016 and 2015 , along with the amount of the impairment. The impairment charges were recorded in Impairment of assets. See Note 1 for additional information. Year Ended December 31, 2017 2016 2015 (Thousands of dollars) Amount of impairment incurred $ 368 $ 407 $ — Combined fair value of assets incurring impairment, after impairment charges $ 1,380 $ 1,380 $ —

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	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 Depreciation expense related to property and equipment was $50.6 million in 2017 , $49.2 million in 2016 , and $46.7 million in 2015 . These amounts are reported as Direct expenses and Selling, general, and administrative expenses in our Consolidated Statements of Operations included elsewhere herein.

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	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

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued and Other Current Liabilities	ACCRUED AND OTHER CURRENT LIABILITIES Accrued and other current liabilities as of December 31 consisted of the following: 2017 2016 (Thousands of dollars) Salaries & wages $ 6,240 $ 5,949 Incentive compensation 8,991 1,576 Income taxes 930 587 Interest 8,108 8,057 Vacation payable 7,619 5,700 Group medical 1,344 1,892 Transportations tax 971 427 Operating lease 710 769 Workers compensation 959 865 Other 5,978 2,524 Total accrued liabilities $ 41,850 $ 28,346

Long Term Debt

Long Term Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long Term Debt	LONG-TERM DEBT The components of long-term debt as of December 31 were as follows: December 31, 2017 December 31, 2016 Principal Unamortized Debt Issuance Debt Cost Principal Unamortized Debt Issuance Debt Cost (Thousands of dollars) Senior Notes issued March 17, 2014, interest only payable semi-annually at 5.25%, maturing March 15, 2019 $ 500,000 $ 1,506 $ 500,000 $ 2,753 Revolving Credit Facility due March 7, 2019 with a group of commercial banks, interest payable at variable rates 117,500 — 134,000 — Total long-term debt $ 617,500 $ 1,506 $ 634,000 $ 2,753 Listed below is information on our future annual maturities of long-term debt (in thousands): 2018 $ — 2019 617,500 2020 — 2021 — 2022 — Thereafter — Total $ 617,500 Senior Notes – The 5.25% Senior Notes (“Notes”) are unconditionally guaranteed on a senior basis by our domestic subsidiaries and are general, unsecured obligations of ours and the subsidiary guarantors. We have the option to redeem some or all of the Notes at specified redemption prices. The Notes contain restrictive covenants, including limitations on incurring indebtedness, creating liens, selling assets, and entering into certain transactions with affiliates. The covenants limit our ability to pay cash dividends on common stock, repurchase or redeem common or preferred equity, prepay subordinated debt, and make certain investments. There are no restrictions on dividends from a subsidiary to the parent company, nor any restrictions on investments in a subsidiary by the parent company. Upon the occurrence of a “Change in Control Repurchase Event” (as defined in the indenture governing the notes), each holder of the Notes will have the right to require us to purchase that holder’s Notes for a cash price equal to 101% of their principal amount. Upon the occurrence of an “Event of Default” (as defined in the indenture), the trustee or the holders of the Notes may declare all of the outstanding Notes to be due and payable immediately. As of December 31, 2017, we were in compliance with the covenants governing the Notes. The Notes bear interest at a fixed rate and therefore changes in market interest rates do not affect our interest payment obligations on the notes. The fair market value of the Notes varies as changes occur to general market interest rates, the remaining maturity of the notes, and our credit worthiness. At December 31, 2017 , the fair market value of Notes was $499.2 million and the carrying value was $500.0 million . At December 31, 2016 , the fair market value of the Notes was $474.4 million , and the carrying value was $500.0 million . Revolving Credit Facility – We have an amended and restated revolving credit facility (our "credit facility") that matures on March 7, 2019. Under our credit facility, we can borrow up to $130.0 million at floating interest rates based on either the London Interbank Offered Rate plus 275 basis points (as defined in our credit facility). Our revolving credit facility includes usual and customary covenants and events of default for credit facilities of its type. Our ability to borrow under the credit facility is conditioned upon our continued compliance with such covenants, including, among others, (i) covenants that restrict our ability to engage in certain asset sales, mergers or other fundamental changes, to incur liens or to engage in certain other transactions or activities and (ii) financial covenants that stipulate that PHI will maintain a consolidated working capital ratio of at least 2 to 1, a net funded debt to consolidated net worth ratio not greater than 1.5 to 1, a fixed charge coverage ratio of at least 1 to 1 if our short term investments fall below $150.0 million , and consolidated net worth of at least $500.0 million (with all such terms or amounts as defined in or determined under the amended and restated revolving credit facility). As of December 31, 2017 , we were in compliance with these covenants. During the fourth quarter of 2017, we amended our credit facility to (i) extend the maturity date of the line of credit from October 1, 2018 to March 7, 2019, (ii) decrease the secured revolving line of credit from $150.0 million to $130.0 million , (iii) limit extensions of credit under the revolving line of credit to a borrowing base calculated periodically based on specified percentages of the value of eligible accounts and eligible inventory and the value of certain short-term investments, and (iv) waive the fixed charge coverage ratio for the fourth quarter of 2017 and the first quarter of 2018. The amendment also amends certain specified interest rates and various covenants including amendments that change the fixed charge coverage ratio from 1.10 to 1.00 to 1.00 to 1.00, calculated on a quarterly basis, change the Company’s required consolidated net worth from $450.0 million to $500.0 million , and permit debt in an aggregate principal amount not to exceed $5.0 million to accommodate an international working capital line of credit. Cash paid to fund interest expense was $30.5 million for the year ended December 31, 2017 , $29.2 million for the year ended December 31, 2016 and $27.7 million for the year ended December 31, 2015. For additional information on our revolving credit facility, see “Management’s Discussion and Analysis of Financial Condition and Results of Operations – Liquidity and Capital Resources – Long Term Debt” included in Item 7 of this report. Impact of Covenants. Our debt covenants could materially adversely affect our ability to operate or expand our business, to pursue strategic transactions, or to otherwise pursue our plans and strategies. Our debt instruments contain cross payment default or cross acceleration provisions. When present, these provisions could have a wider impact on liquidity than might otherwise arise from a default or acceleration of a single debt instrument. Our ability to comply with the financial covenants in our credit facility could be adversely impacted by a wide variety of events, including unforeseen contingencies, many of which are beyond our control. Other - We maintain a separate letter of credit facility that had $12.4 million in letters of credit outstanding at December 31, 2017 , compared to $13.0 million in letters of credit outstanding at December 31, 2016 . The letters of credit securing our workers compensation policies, in the amount of $3.2 million , are evergreen. The letter of credit securing an Air Medical traditional provider contract, in the amount of $9.2 million , expires on October 29, 2018. We also have outstanding a letter of credit for $7.6 million issued under our $130.0 million credit facility that reduces the amount we can borrow under that facility. This letter of credit was issued to guarantee our performance under a contract that was awarded in late 2017 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES For financial reporting purposes, (loss) earnings before income taxes includes the following components: Year Ended December 31, 2017 2016 2015 (Thousands of dollars) United States $ (50,871 ) $ (25,604 ) $ 45,038 Foreign (570 ) (1,546 ) (1,782 ) Total (51,441 ) (27,149 ) 43,256 The provision for income taxes for 2017, 2016, and 2015 consisted of the following: Year Ended December 31, 2017 2016 2015 (Thousands of dollars) U.S. Federal: Current $ — $ — $ — Deferred (57,637 ) (5,488 ) 13,629 (57,637 ) (5,488 ) 13,629 U.S. State: Current $ 199 $ 427 $ 284 Deferred $ (717 ) $ 3,218 $ (740 ) $ (518 ) $ 3,645 $ (456 ) Foreign: Current $ 108 $ 1,374 $ 3,159 Deferred $ (926 ) — — $ (818 ) $ 1,374 $ 3,159 Provision for income taxes $ (58,973 ) $ (469 ) $ 16,332 Income tax expense as a percentage of pre-tax earnings varies from the effective Federal statutory rate of 35% as a result of the following: Year Ended Year Ended Year Ended (Thousands of dollars, except percentage amounts) Amount Tax Amount Tax Amount Tax Income taxes at statutory rate $ (18,004 ) 35 $ (9,502 ) 35 $ 15,140 35 Increase (decrease) in taxes resulting from: Valuation allowance on foreign tax credits 6,145 (12 ) 8,991 (33 ) — — Valuation allowance on state net operating loss carryforwards 868 (2 ) 5,028 (19 ) — — Valuation allowance reversal–investment in foreign entity — — — (456 ) (1 ) Valuation Allowance - Other 1,353 (3 ) — — — — Change in tax rate on deferred items — — (4,772 ) 18 1,078 3 % Tax reform – Impact of change in tax rate (49,219 ) 96 — — — — State income taxes, net of federal benefit (1,386 ) 3 (1,384 ) 5 146 — Other items – net 1,270 (2 ) 1,170 (4 ) 424 1 Total $ (58,973 ) 115 $ (469 ) 2 $ 16,332 38 On December 22, 2017, the Tax Cuts and Jobs Act (the “Tax Act”) was enacted which significantly reformed the U.S. Internal Revenue Code (the “Code”). The Tax Act, among other things, reduces the federal corporate income tax rate from 35% to 21% effective January 1, 2018, imposes significant additional limitations on the deductibility of interest, allows for the expensing of capital expenditures, migrates the Code from a “worldwide” system of taxation to a territorial system and modifies or repeals many business deductions and credits. The change in rates required us under applicable accounting rules to remeasure our deferred tax assets and liabilities, and to recognize the impact of this remeasurement in the period of enactment of the rate change. As a result of the rate changes in late 2017, we remeasured our net deferred tax liability at December 31, 2017, and provisionally recognized a net benefit of $49.2 million in our consolidated statement of operations for the year ended December 31, 2017. The Tax Act imposed a one-time repatriation tax on certain earnings of foreign subsidiaries. We do not expect this one-time tax to materially impact us, and have provisionally recorded no liability relating to this one-time repatriation tax in our consolidated statement of operations for the year ended December 31, 2017. We continue to examine the impact of other provisions of the Tax Act on our business. On December 22, 2017, the SEC staff addressed the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. We have provisionally recognized the tax impacts related to the remeasurement of deferred tax assets and liabilities and the effect of the repatriation tax in the amounts noted above in our consolidated financial statements for the year ended December 31, 2017. The ultimate impact of the Tax Act may differ from our provisional amounts due to additional analysis, changes in interpretations and assumptions we have made, additional regulatory guidance that may be issued, and actions we may take as a result of the Tax Act. The change from our current provisional estimates will be reflected in our future statements of operations. We expect to complete the accounting by the time we file our 2017 U.S. corporate income tax return in the 3rd quarter of 2018. In 2016 and 2015, the change in tax rate on deferred items is mainly related to increases or reductions in the estimated effective tax rate that will be present at the time the deferred tax assets and liabilities reverse for tax purposes. The increase is attributable to an increase in the apportionment percentages in the various jurisdictions in which we operate as a result of increased operations in certain states. The reduction is attributable to a decline in the apportionment percentages in the various jurisdictions in which we operate, primarily as a result of a change in law related to apportionment factor calculations in one jurisdiction and a change in the composition of earnings in the various jurisdictions in which we operate. In 2016 and 2015, the overall impact of state apportionment percentage changes was a tax benefit of $4.8 million and tax expense of $1.0 million , respectively. In 2017, the impact of state apportionment changes are included within the overall provisional net benefit described above. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The tax effects of significant items comprising our net deferred tax balance at December 31 are as follows: 2017 2016 (Thousands of dollars) Deferred tax assets: Deferred compensation $ 626 $ 937 Foreign tax credits 19,453 21,492 Vacation and bonus accrual 3,936 1,674 Inventory valuation 4,954 7,655 Rental accrual 747 1,416 Hurricane relief credit 1,255 1,255 Stock-based compensation 988 2,202 Other 2,235 3,115 Net operating losses 82,044 89,256 Total deferred tax assets 116,238 129,002 Valuation allowance – state NOL carryforwards (5,998 ) (5,318 ) Valuation allowance – tax credit carryforwards (16,537 ) (11,039 ) Valuation allowance – foreign NOL carryforwards (98 ) — Total deferred tax assets, net 93,605 112,645 Deferred tax liabilities: Tax depreciation in excess of book depreciation (171,116 ) (253,560 ) Other (5,185 ) — Total deferred tax liabilities (176,301 ) (253,560 ) Net deferred tax liabilities $ (82,696 ) $ (140,915 ) Deferred tax assets – short-term — 10,798 Deferred tax assets – long-term 3,309 — Deferred tax liability – long-term (86,005 ) (151,713 ) Net deferred tax liabilities $ (82,696 ) $ (140,915 ) The Company has U.S. Federal net operating loss carryforwards (“NOLs”) of approximately $297.2 million that, if not used, will expire beginning in 2026 through 2037 . Additionally, for state income tax purposes, the Company has NOLs of approximately $239.5 million available to reduce future state taxable income. These NOLs expire in varying amounts through 2037 , the majority of which expire in 2024 through 2037 . The Company had a valuation allowance of $6.0 million as of December 31, 2017 against certain net operating losses in six states which we have determined are more likely than not to be forfeited in future years. During 2017 , the Company recorded $0.9 million of valuation allowances on state NOLs. The Company’s deferred income tax balance as of December 31, 2017 includes deferred tax balances related to foreign entities that were acquired by the Company pursuant to the purchase of the HNZ Group Inc.’s offshore business on December 29, 2017. As of December 31, 2017, the Company has $3.3 million of net deferred tax assets related to its acquired Australian operation and $0.2 million of net deferred tax liabilities related to its acquired New Zealand operation. The net deferred tax assets related to Australia is mainly comprised of net operating losses of approximately $14.5 million that, if not used, can be carried forward indefinitely. The Company also has foreign tax credits of approximately $19.5 million and general business credits of approximately $1.3 million which expire at various dates through 2028. The estimated future U.S. taxable income, after utilization of the available net operating loss carryforwards, will limit the ability of the Company to utilize some of the foreign tax credit carryforwards during their carry forward period and it is not more likely than not that a portion of these credits will be utilized in future years. Therefore, the Company has a valuation allowance of $16.6 million on these credits, $7.5 million of which was recorded in 2017 . The increase in the valuation allowance is attributable to a change in estimate where it has been determined that the tax credits will expire before being fully utilized. The Company files income tax returns in the U.S. federal jurisdiction and in many U.S. state jurisdictions. The tax years 2014 to 2017 remain open to examination by the major taxing jurisdictions in which the Company is subject to tax. Income taxes paid were approximately $1.2 million , $2.6 million , and $5.5 million for each of the years ended December 31, 2017 , 2016 , and 2015, respectively. At December 31, 2017 , the Company had no unrecognized tax benefits. It is the Company’s practice to recognize interest and penalties related to income tax expense as part of non-operating expenses.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The components of basic and diluted earnings per share for the years ended December 31, are as follows: 2017 2016 2015 (in thousands) Weighted average outstanding shares of common stock, basic 15,762 15,663 15,566 Dilutive effect of unvested restricted stock units — — 76 Weighted average outstanding shares of common stock, diluted 15,762 15,663 15,642 For the year ended December 31, 2017 , there were no unvested restricted stock units excluded from the weighted average outstanding shares of common stock, diluted. There were 24,468 shares of stock that were anti-dilutive to earnings for the year ended December 31, 2016 and none in 2015 .

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Postemployment Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS Deferred Compensation Plan The Company maintains an Officer Deferred Compensation Plan that permits key officers to defer a portion of their compensation. The plan is nonqualified and we are not obligated to fund it. The Company has established a separate bookkeeping account for each participant, which is treated as if invested and reinvested from time to time in investments that the participant selects from a list of available investment choices. These accruals are periodically adjusted for gains and losses to reflect the performance of the hypothetical investments. Earnings and losses on the book reserve accounts accrue to the plan participants. Liabilities for the plan are included in other long-term liabilities, and the corresponding investment accounts funded by voluntary contributions are included in other assets. Aggregate amounts deferred under the plans were $2.7 million and $2.4 million for the years ended December 31, 2017 and 2016 , respectively. Incentive Compensation The Company has one incentive compensation plan. The incentive compensation plan for non-executive employees allows the Company to pay up to 3.00% of the employee's annual earnings upon achieving a specified earnings threshold. The Company also has an executive/senior management plan for certain corporate and business unit management employees. Under this plan, the bonus is a percentage of each participating employee’s base salary based upon the each segment’s achievement of the financial target established by the Board of Directors at three levels – a threshold level, a target level, and a stretch level, subject to a positive or negative adjustment for the Company’s safety performance. Pursuant to these plans, the Company accrued incentive compensation expense of $9.0 million , $1.6 million , and $3.0 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. We also have a Safety Incentive Plan related to Occupational Safety and Health Administration recordable incidents, for which we expensed and paid $0.6 million , $0.9 million , and $0.9 million for the years 2017 , 2016 , and 2015 , respectively. 401(k) Plan We sponsor a 401(k) Plan (“Plan”) for our employees. An employee is eligible to participate in the Plan immediately upon employment and receive a dollar matching contribution up to 6% of his or her base compensation. The vesting for matching contributions is 25% per year beginning at the end of the second year of employment. Employees are fully vested after completing five years of service to the Company. The matching contribution for the years ended December 31, 2017 , 2016 , and 2015 were $9.5 million , $10.1 million , and $11.8 million , respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Compensation expense for our stock-based plans was $4.4 million , $(0.1) million , and $5.8 million for 2017 , 2016 , and 2015 , respectively. 2012 Long-Term Incentive Plan – Under our Second Amended and Restated Long-Term Incentive Plan (“LTIP”), we are authorized to issue up to 3,500,000 shares of non-voting stock. As of December 31, 2017 , 1,806,315 shares remained available for grant. Time-vested restricted stock units granted under the LTIP generally have forfeiture restrictions that lapse 100% after three years. Performance-based restricted stock units that have been granted under the LTIP, whose vesting is contingent upon meeting company-wide performance goals, have forfeiture restrictions that lapse, at the end of a three-year performance period if all performance and continued service conditions are met. Non-Voting Time-Vested Restricted Stock Units – The following table summarizes the activity for non-voting time-vested restricted stock units granted to employees for the year ended December 31, 2017 . Share Units Weighted Average Grant-Date Fair Value Remaining Average Contractual Life ( in years) Aggregate Value ( in thousands) Outstanding at January 1, 2017 202,560 $ 37.91 1.25 $ 7,679 Granted 480,065 11.42 Forfeited (10,211 ) 10.01 Vested and released to participants (137,703 ) 41.76 Outstanding at December 31, 2017 534,711 $ 12.80 2.26 $ 6,844 The weighted average grant-date fair value of time-vested restricted stock units granted during 2017 and 2016 was $11.42 and $20.07 per share, respectively. The total fair value of awards that vested in 2017 was $1.5 million . The total fair value of awards that vested in 2016 was $0.2 million . The total fair value of awards forfeited in 2017 was $0.4 million . The total fair value of awards forfeited in 2016 was $0.1 million . As of December 31, 2017 , there was $4.1 million that is expected to be recognized over a weighted average period of 2.26 years. The following table summarizes the activity for non-voting time-vested restricted stock units granted to non-employee directors for the year ended December 31, 2017 . Share Units Weighted Average Grant-Date Fair Value Remaining Average Contractual Life (in years) Aggregate Value (in thousands) Outstanding at January 1, 2017 11,559 $ 23.01 2.13 $ 266 Granted 10,323 11.91 Forfeited — — Vested and released to participants (2,202 ) 44.04 Outstanding at December 31, 2017 19,680 $ 14.94 2.71 $ 292 Non-Voting Performance-Based Restricted Stock Units – The following table summarizes the activity for non-voting performance-based restricted stock units for the year ended December 31, 2017 . Share Units Weighted Average Grant-Date Fair Value Remaining Average Contractual Life ( in years) Aggregate Value ( in thousands) Outstanding at January 1, 2017 569,418 $ 25.83 1.19 $ 14,708 Granted 371,045 15.11 Forfeited (122,313 ) 41.64 Vested and released to participants — — Outstanding at December 31, 2017 818,150 $ 18.60 1.20 $ 15,218 The aggregate value of the awards in the above table reflects the impact of current expectations of achievement through the end of the performance cycle. The average grant-date fair value of performance based restricted stock units granted during 2017 was $15.11 per share. The total fair value of awards that vested in 2017 was $0 . Total fair value of awards forfeited in 2017 was $5.1 million . As of December 31, 2016, the Company determined that the performance thresholds set for the performance based restricted stock units were unlikely to be met. As a result, we recorded a $2.8 million reduction in compensation expense. As of December 31, 2017 , there was a total of $3.3 million of unrecognized compensation cost related to the non-vested performance-based restricted stock units.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Operating Leases The Company leases certain aircraft, facilities, and equipment used in its operations. The related lease agreements, which include both non-cancelable and month-to-month terms, generally provide for fixed monthly rentals and, for certain real estate leases, renewal options. The Company generally pays all insurance, taxes, and maintenance expenses associated with these aircraft leases and some of these leases contain renewal and purchase options at fair market values. Rental expense incurred under these leases consisted of the following: Year Ended Year Ended Year Ended (Thousands of dollars) Aircraft $ 39,815 $ 44,130 $ 45,360 Other 9,504 9,451 8,358 Total $ 49,319 $ 53,581 $ 53,718 The following table presents the remaining aggregate lease commitments under operating leases having initial non-cancelable terms in excess of one year as of December 31, 2017. The table includes renewal periods on the principal operating facility lease. Aircraft Other Total (Thousands of dollars) 2018 $ 35,723 $ 5,157 $ 40,880 2019 31,245 3,670 34,915 2020 27,406 3,308 30,714 2021 27,272 2,468 29,740 2022 26,758 1,153 27,911 Thereafter 29,077 9,832 38,909 $ 177,481 $ 25,588 $ 203,069 Purchase Options As of December 31, 2017 , we had options to purchase aircraft under lease becoming exercisable in 2018 through 2022 . The aggregate option purchase prices are $127.0 million in 2018 , $129.0 million in 2019 , and $22.7 million in 2020 . Under current conditions, we believe that it is unlikely that we will exercise the 2018 purchase options. Whether we exercise the remaining options will depend upon several factors, including market conditions and our available cash at the respective exercise dates. Guarantees In the normal course of business with customers, vendors, and others, we provide guarantees, performance, and payment bonds pursuant to certain agreements. The aggregate amount of these guarantees and bonds at December 31, 2017 was $1.0 million . Purchase Commitments Total aircraft deposits of $0.5 million were included in Other Assets as of December 31, 2017 . This amount represents deposits for aircraft purchase contracts and deposits on future lease buyout options. In the event the buyout options are not exercised, the deposits will be applied as lease payments. Environmental Matters PHI has recorded an estimated liability of $0.15 million as of December 31, 2017 for environmental response costs. Previously, PHI conducted environmental surveys of its former Lafayette Facility located at the Lafayette Regional Airport, which former facility PHI vacated in 2001, and determined that limited soil and groundwater contamination exist at two parcels of land at the former facility. An Assessment Report for both parcels was submitted in 2003 (and updated in 2006) to the Louisiana Department of Environmental Quality (LDEQ) and the Louisiana Department of Natural Resources (LDNR). Approvals for the Assessment Report were received from the LDEQ and LDNR in 2010 and 2011, respectively. Since that time, PHI has performed groundwater sampling of the required groundwater monitor well installations at both former PHI facility parcels and submitted these sampling reports to the LDEQ. Pursuant to an agreement with the LDEQ, PHI provided groundwater sample results semi-annually to the LDEQ for both former PHI facility parcels from 2005 to 2015. LDEQ approved a reduction in the sampling program from semi-annual to annual groundwater monitoring in 2015. Based on PHI’s working relationship and agreements with the LDEQ, and the results of ongoing former facility parcel monitoring, PHI believes that ultimate remediation costs for the subject parcels will not be material to PHI’s consolidated financial position, operations or cash flows. Legal Matters On September 25, 2017, we brought a suit in the U.S. District Court for the Western District of Louisiana against Office & Professional Employees International Union and Office & Professional Employees International Union, Local 108 (Civil Action No. 6:17 cv 01216), which collectively represent our domestic pilot workforce. In this suit, we sought declaratory relief and other remedies under federal law to confirm that we could increase the wages of most of our unionized pilots and provide enhanced benefits of employment without negotiating these proposed changes with the defendants. On February 20, 2018, we dismissed our suit without prejudice in connection with the defendants' withdrawal of their prior demand to negotiate these charges. From time to time, we are involved in various legal actions incidental to our business, including actions relating to employee claims, actions relating to medical malpractice claims, various tax issues, grievance hearings before labor regulatory agencies, and miscellaneous third party tort actions. The outcome of these proceedings is not predictable. However, based on current circumstances, we do not believe that the ultimate resolution of these proceedings, after considering available defenses and any insurance coverage or indemnification rights, will have a material adverse effect on our financial position, results of operations or cash flows.

Business Segments and Geographi

Business Segments and Geographic Areas	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments and Geographic Areas	BUSINESS SEGMENTS AND GEOGRAPHIC AREAS Under Accounting Standards Codification 280, “Segment Reporting,” we have determined that we have the following three reportable segments: • Oil and Gas • Air Medical • Technical Services. A segment’s operating profit or loss is its operating revenues less its direct expenses and selling, general and administrative expenses. Each segment has a portion of selling, general and administrative expenses that is charged directly to the segment and a portion that is allocated. Direct charges represent the vast majority of segment selling, general and administrative expenses. Allocated selling, general and administrative expenses is based primarily on total segment costs as a percentage of total operating costs. In addition, a portion of our selling, general and administrative expenses are not allocated to any segment. The Oil and Gas segment provides helicopter services to oil and gas customers operating in the Gulf of Mexico and a selected number of foreign countries. The Air Medical segment provides helicopter services to hospitals and emergency service providers in several U.S. states, and individuals, in which case the Company is paid by either a commercial insurance company, federal or state agency, or the patient. The Technical Services segment provides helicopter repair and overhaul services for existing flight operations customers that own their own aircraft. Under this segment, the Company periodically provides certain services to governmental customers, including the Company’s agreement to operate six aircraft for the National Science Foundation in Antarctica. Under this segment, we also offer certain software as a service to our Oil and Gas customers. Air Medical operations are headquartered in Phoenix, Arizona, where the Company maintains significant separate facilities and administrative staff dedicated to this segment. Those costs are charged directly to the Air Medical segment, resulting in a disproportionate share of selling, general and administrative expenses compared to the Company’s other reportable 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 % The following table shows information about the profit or loss and assets of each of the Company’s reportable segments for the years ended December 31, 2017 , 2016 , and 2015 . The information contains certain allocations, including allocations of depreciation, rents, insurance, and overhead expenses that the Company deems reasonable and appropriate for the evaluation of its results of operations. The Company does not allocate gains on dispositions of property and equipment, other income, interest expense, income taxes, and corporate selling, general, and administrative expenses to its segments. Where applicable, the tables present the unallocated amounts to reconcile the totals to the Company’s consolidated financial statements. Corporate assets are principally cash, short-term investments, other assets, and certain property and equipment. 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. 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 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 As discussed in Note 2 to our accompanying financial statements, on December 31, 2017 we acquired the HNZ Offshore Business. Certain of those foreign customers pay us less promptly and regularly than our domestic customers. To date, these payment delays and irregularities have not resulted in any material losses. Nonetheless, these payment delays and irregularities have, among other things, disrupted our cash flows and exposed us to greater risks of non-payment, and could in the future potentially have a material adverse effect upon our financial position, liquidity, business or results of operations.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	QUARTERLY FINANCIAL DATA (UNAUDITED) The condensed quarterly results of operations for the years ended December 31, 2017 and 2016 (in thousands of dollars, except per share data) were as follows: Quarter Ended March 31, June 30, September 30, December 31, 2017 2017 2017 2017 (Thousands of dollars, except per share data) Operating revenues, net $ 134,618 $ 146,424 $ 150,167 $ 148,336 (Loss) gain on disposition of assets, net — 7 4 287 (Loss) earnings before income taxes (23,073 ) (3,150 ) (4,899 ) (20,319 ) Net (loss) earnings (15,248 ) (3,273 ) (3,277 ) 29,330 Net (loss) earnings per share Basic (0.97 ) (0.21 ) (0.21 ) 1.87 Diluted (0.97 ) (0.21 ) (0.21 ) 1.87 Quarter Ended March 31, June 30, September 30, December 31, 2016 2016 2016 2016 (Thousands of dollars, except per share data) Operating revenues, net $ 164,016 $ 167,136 $ 158,093 $ 144,853 Gain (loss) on disposition of assets, net (359 ) 4,298 (85 ) (504 ) Earnings before income taxes (7,488 ) 117 (7,766 ) (12,012 ) Net earnings (8,932 ) 4,277 (4,967 ) (17,058 ) Net earnings per share Basic (0.57 ) 0.27 (0.32 ) (1.08 ) Diluted (0.57 ) 0.27 (0.32 ) (1.08 )

Variable Interest Entity

Variable Interest Entity	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entity	INVESTMENT IN VARIABLE INTEREST ENTITY AND OTHER INVESTMENTS AND AFFILIATES We account for our investment in certain international operations as variable interest entities, which is defined as an entity that either (a) has insufficient equity to permit the entity to finance its operations without additional subordinated financial support or (b) has equity investors who lack the characteristics of a controlling financial interest. PHI Century Limited - As of December 31, 2017 , we had a 49% investment in the common stock of PHI Century Limited (“PHIC”), a Ghanaian entity. We acquired our 49% interest on May 26, 2011 , PHIC’s date of incorporation. The purpose of PHIC is to provide oil and gas flight services in Ghana and the West African region. For the year ended December 31, 2017 , we recorded a loss in equity of this unconsolidated affiliate of $1.0 million relative to our 49% equity ownership. We had $4.0 million of trade receivables as of December 31, 2017 from PHIC. Our investment in the common stock of PHIC is included in Other Assets on our Condensed Consolidated Balance Sheets and was $0.3 million and $0.2 million at December 31, 2017 and December 31, 2016 respectively. PHI-HNZ Australia Ltd - In the fourth quarter of 2016, the Company and HNZ Group, Inc. ("HNZ") jointly formed PHI-HNZ Australia Pty Ltd. ("PHI-HNZ"), a legal entity held 50% by PHI, Inc. and 50% by HNZ, to provide helicopter transportation services in support of a gas development project offshore of western Australia. PHI-HNZ began operations in April, 2017. For the year ended December 31, 2017 , we recorded a gain in equity of this unconsolidated affiliate of $0.6 million . As a result of the acquisition of the HNZ Offshore Business on December 29, 2017, we now own 100% of PHI-HNZ.

Condensed Consolidating Financi

Condensed Consolidating Financial Information - Guarantor Subsidiaries	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Consolidating Financial Information - Guarantor Subsidiaries	CONDENSED CONSOLIDATING FINANCIAL INFORMATION – GUARANTOR SUBSIDIARIES As discussed further in Note 4, on March 17, 2014, PHI, Inc. issued $500.0 million aggregate principal amount of 5.25% Senior Notes due 2019 that are fully and unconditionally guaranteed on a joint and several, senior basis by all of PHI, Inc.’s domestic subsidiaries. PHI, Inc. directly or indirectly owns 100% of all of its domestic subsidiaries. The supplemental condensed financial information on the following pages sets forth, on a consolidated basis, the balance sheet, statement of operations, statement of comprehensive income, and statement of cash flows information for PHI, Inc. (“Parent Company”) the guarantor subsidiaries and the non-guarantor subsidiaries, each under separate headings. The eliminating entries eliminate investments in subsidiaries, intercompany balances, and intercompany revenues and expenses. The condensed consolidating financial statements have been prepared on the same basis as the consolidated financial statements of PHI, Inc. The equity method is followed by the Parent Company within the financial information presented below. The transactions reflected in “Due to/from affiliates, net” in the following condensed consolidated statements of cash flows primarily consist of centralized cash management activities between PHI, Inc. and its subsidiaries, pursuant to which cash earned by the guarantor subsidiaries is regularly transferred to PHI, Inc. to be centrally managed. Because these balances are treated as short-term borrowings of the Parent Company, serve as a financing and cash management tool to meet our short-term operating needs, turn over quickly and are payable to the guarantor subsidiaries on demand, we present borrowings and repayments with our affiliates on a net basis within the condensed consolidating statement of cash flows. Net receivables from our affiliates are considered advances and net payables to our affiliates are considered borrowings, and both changes are presented as financing activities in the following condensed consolidating statements of cash flows. Due to the growth of our international affiliates in Trinidad and Australia which no longer qualify as minor subsidiaries under regulation S-X 210.3-10(h)6, we began reporting all of our non-guarantors subs in a separate column beginning with the quarter ended June 30, 2017. We have recast prior years financial information to conform to current year presentation. PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS (Thousands of dollars) December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated ASSETS Current Assets: Cash $ 47 $ 1,072 $ 7,651 $ — $ 8,770 Short-term investments 64,237 — — — 64,237 Accounts receivable – net 90,077 74,886 38,020 (17,004 ) 185,979 Intercompany receivable — 126,366 — (126,366 ) — Inventories of spare parts – net 68,737 9,049 3,095 — 80,881 Prepaid expenses 8,348 1,898 1,229 — 11,475 Deferred income taxes — — — — — Income taxes receivable 345 9 917 — 1,271 Total current assets 231,791 213,280 50,912 (143,370 ) 352,613 Investment in subsidiaries and others 397,301 — — (397,301 ) — Property and equipment – net 617,488 284,984 44,293 — 946,765 Restricted cash and investments 12,382 — 14 — 12,396 Other assets 139,754 908 (131,921 ) — $ 8,741 Deferred income tax — — 3,309 — 3,309 Goodwill — — 61,299 — $ 61,299 Intangible assets — — 16,723 — 16,723 Total assets $ 1,398,716 $ 499,172 $ 44,629 $ (540,671 ) $ 1,401,846 LIABILITIES AND SHAREHOLDERS’ EQUITY Current Liabilities: Accounts payable $ 28,130 $ 4,636 $ 21,425 $ (17,005 ) $ 37,186 Accrued and other current liabilities 23,147 10,577 8,126 — 41,850 Intercompany payable 113,387 — 12,978 (126,365 ) — Total current liabilities 164,664 15,213 42,529 (143,370 ) 79,036 Long-term debt 615,994 — — — 615,994 Deferred income taxes and other long-term liabilities 5,404 84,300 4,458 — 94,162 Shareholders’ Equity: Common stock and paid-in capital 309,933 77,951 1,375 (79,326 ) 309,933 Accumulated other comprehensive loss (280 ) — — — (280 ) Retained earnings 303,001 321,708 (3,733 ) (317,975 ) 303,001 Total shareholders’ equity 612,654 399,659 (2,358 ) (397,301 ) 612,654 Total liabilities and shareholders’ equity $ 1,398,716 $ 499,172 $ 44,629 $ (540,671 ) $ 1,401,846 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS (Thousands of dollars) December 31, 2016 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated ASSETS Current Assets: Cash $ 36 $ 2,100 $ 460 $ — $ 2,596 Short-term investments 289,806 — — — 289,806 Accounts receivable – net 71,458 62,868 3,939 — 138,265 Intercompany receivable — 91,040 (33,136 ) (57,904 ) — Inventories of spare parts – net 61,834 8,568 — — 70,402 Prepaid expenses 6,990 2,184 85 — 9,259 Deferred income taxes 10,798 — — — 10,798 Income taxes receivable 558 (18 ) — — 540 Total current assets 441,480 166,742 (28,652 ) (57,904 ) 521,666 Investment in subsidiaries 353,160 — — (353,160 ) — Property and equipment – net 589,104 294,197 20,676 — 903,977 Restricted investments 13,023 — 15 — 13,038 Other assets 8,660 1,099 — — 9,759 Total assets $ 1,405,427 $ 462,038 $ (7,961 ) $ (411,064 ) $ 1,448,440 LIABILITIES AND SHAREHOLDERS’ EQUITY Current Liabilities: Accounts payable $ 22,744 $ 5,822 $ 138 $ — $ 28,704 Accrued liabilities 18,725 9,418 203 — 28,346 Intercompany payable 57,904 — — (57,904 ) — Total current liabilities 99,373 15,240 341 (57,904 ) 57,050 Long-term debt 631,247 — — — 631,247 Deferred income taxes and other long-term liabilities 75,029 85,336 — — 160,365 Shareholders’ Equity: Common stock and paid-in capital 305,815 77,951 1,240 (79,191 ) 305,815 Accumulated other comprehensive loss (478 ) — — — (478 ) Retained earnings 294,441 283,511 (9,542 ) (273,969 ) 294,441 Total shareholders’ equity 599,778 361,462 (8,302 ) (353,160 ) 599,778 Total liabilities and shareholders’ equity $ 1,405,427 $ 462,038 $ (7,961 ) $ (411,064 ) $ 1,448,440 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Thousands of dollars) For the year ended December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Operating revenues, net $ 310,449 $ 262,229 $ 23,871 $ (17,004 ) $ 579,545 Expenses: Direct expenses 326,152 212,691 24,860 (17,004 ) 546,699 Selling, general, and administrative expenses 41,134 12,462 221 — 53,817 Total operating expenses 367,286 225,153 25,081 (17,004 ) 600,516 Loss on disposition of assets, net 300 (2 ) — — 298 Impairment of assets 368 — — — 368 Equity in loss of unconsolidated affiliate 1,021 — (636 ) — 385 Operating (loss) income (58,526 ) 37,078 (574 ) — (22,022 ) Equity in net earnings of consolidated subsidiaries (38,553 ) — — 38,553 — Interest expense 32,161 22 — — 32,183 Other income, net (2,757 ) (2 ) (5 ) — (2,764 ) (9,149 ) 20 (5 ) 38,553 29,419 (Loss) earnings before income taxes (49,377 ) 37,058 (569 ) (38,553 ) (51,441 ) Income tax (benefit) expense (56,909 ) (1,138 ) (926 ) — (58,973 ) Net earnings (loss) $ 7,532 $ 38,196 $ 357 $ (38,553 ) $ 7,532 For the year ended December 31, 2016 Parent Non- Company Guarantor Guarantor Only (issuer) Subsidiaries Subsidiaries Eliminations Consolidated Operating revenues, net $ 339,829 $ 293,329 $ 940 $ — $ 634,098 Expenses: Direct expenses 347,532 237,635 7,383 — 592,550 Selling, general, and administrative expenses 32,911 10,984 541 (18 ) 44,418 Total operating expenses 380,443 248,619 7,924 (18 ) 636,968 Gain on disposition of assets, net (3,350 ) — — — (3,350 ) Impairment of assets 407 — — — 407 Equity in profit of unconsolidated affiliate (151 ) — — — (151 ) Operating (loss) income (37,520 ) 44,710 (6,984 ) 18 224 Equity in net earnings of consolidated subsidiaries (22,182 ) — — 22,182 — Interest expense 30,585 46 13 — 30,644 Other income, net (3,284 ) (5 ) — 18 (3,271 ) 5,119 41 13 22,200 27,373 (Loss) earnings before income taxes (42,639 ) 44,669 (6,997 ) (22,182 ) (27,149 ) Income tax (benefit) expense (15,959 ) 15,490 — — (469 ) Net (loss) earnings $ (26,680 ) $ 29,179 $ (6,997 ) $ (22,182 ) $ (26,680 ) PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Thousands of dollars) For the year ended December 31, 2015 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Operating revenues, net $ 476,969 $ 327,259 $ — $ — $ 804,228 Expenses: Direct expenses 426,239 259,198 1,631 (18 ) 687,050 Selling, general, and administrative expenses 35,694 10,577 151 — 46,422 Total operating expenses 461,933 269,775 1,782 (18 ) 733,472 Loss on disposition of assets, net 339 — — 339 Equity in loss of unconsolidated affiliate 306 — — 306 Operating income 14,391 57,484 (1,782 ) 18 70,111 Equity in net earnings of consolidated subsidiaries (31,225 ) — — 31,225 — Interest expense 28,946 120 — — 29,066 Other income, net (2,222 ) (7 ) — 18 (2,211 ) (4,501 ) 113 — 31,243 26,855 Earnings before income taxes 18,892 57,371 (1,782 ) (31,225 ) 43,256 Income tax (benefit) expense (8,032 ) (24,364 ) — — 16,332 Net earnings $ 26,924 $ 33,007 $ (1,782 ) $ (31,225 ) $ 26,924 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME (Thousands of dollars) For the year ended December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Net earnings $ 7,532 $ 38,196 $ 357 $ (38,553 ) $ 7,532 Unrealized gain on short-term investments 310 — — — 310 Changes in pension plan assets and benefit obligations (3 ) — — — (3 ) Tax effect (109 ) — — — (109 ) Total comprehensive income $ 7,730 $ 38,196 $ 357 $ (38,553 ) $ 7,730 For the year ended December 31, 2016 Parent Non- Company Guarantor Guarantor Only Subsidiaries Subsidiaries Eliminations Consolidated Net (loss) earnings $ (26,680 ) $ 29,179 $ (6,997 ) $ (22,182 ) $ (26,680 ) Unrealized gain on short-term investments 241 — — — 241 Changes in pension plan assets and benefit obligations (39 ) — — — (39 ) Tax effect (113 ) — — — (113 ) Total comprehensive (loss) income $ (26,591 ) $ 29,179 $ (6,997 ) $ (22,182 ) $ (26,591 ) For the year ended December 31, 2015 Parent Non- Company Guarantor Guarantor Only Subsidiaries Subsidiaries Eliminations Consolidated Net earnings $ 26,924 $ 33,007 $ (1,782 ) $ (31,225 ) $ 26,924 Unrealized loss on short-term investments (641 ) — — — (641 ) Other unrealized gain 24 — — — 24 Changes in pension plan assets and benefit obligations 7 — — — 7 Tax effect 254 — — — 254 Total comprehensive income $ 26,568 $ 33,007 $ (1,782 ) $ (31,225 ) $ 26,568 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (Thousands of dollars) For the year ended December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Net cash (used in) provided by operating activities $ (62,581 ) $ 40,628 $ 2,850 $ — $ (19,103 ) Investing activities: Purchase of property and equipment (56,757 ) — — — (56,757 ) Proceeds from asset dispositions 1,296 — — — 1,296 Purchase of short-term investments (637,980 ) — — — (637,980 ) Proceeds from sale of short-term investments 862,942 — — — 862,942 Payments of deposits on aircraft — — — — — Loan to unconsolidated affiliate — — — — — Loan to third party (824 ) — — — (824 ) Business acquisitions and investments, net of cash (130,788 ) — 4,144 — (126,644 ) Net cash provided by investing activities 37,889 — 4,144 — 42,033 Financing activities: Repurchase of common stock (256 ) — — — (256 ) Proceeds on line of credit 152,150 — — — 152,150 Payments on line of credit (168,650 ) — — — (168,650 ) Due to/from affiliate, net 41,459 (41,656 ) 197 — — Net cash (used in) provided by financing activities 24,703 (41,656 ) 197 — (16,756 ) Increase (decrease) in cash 11 (1,028 ) 7,191 — 6,174 Cash, beginning of year 36 2,100 460 — 2,596 Cash, end of year $ 47 $ 1,072 $ 7,651 $ — $ 8,770 (1) Net of the effect of business acquisitions. PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (Thousands of dollars) For the year ended December 31, 2016 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Net cash (used in) by operating activities $ (46,738 ) $ 52,873 $ (6,699 ) $ — $ (564 ) Investing activities: Purchase of property and equipment (81,484 ) — (358 ) — (81,842 ) Proceeds from asset dispositions 14,983 — — — 14,983 Purchase of short-term investments (321,453 ) — — — (321,453 ) Proceeds from sale of short-term investments 316,543 — — — 316,543 Payments of deposits on aircraft (2,249 ) — — — (2,249 ) Loan to unconsolidated affiliate (1,200 ) — — — (1,200 ) Net cash used in investing activities (74,860 ) — (358 ) — (75,218 ) Financing activities: Repurchase of common stock (529 ) — — — (529 ) Proceeds on line of credit 264,700 — — — 264,700 Payments on line of credit (188,200 ) — — — (188,200 ) Due to/from affiliate, net 45,617 (52,445 ) 6,828 — — Net cash provided by (used in) financing activities 121,588 (52,445 ) 6,828 — 75,971 (Decrease) increase in cash (10 ) 428 (229 ) — 189 Cash, beginning of year 46 1,672 689 — 2,407 Cash, end of year $ 36 $ 2,100 $ 460 $ — $ 2,596 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (Thousands of dollars) For the year ended December 31, 2015 Parent Guarantor Non- Eliminations Consolidated Net cash provided by operating activities $ 60,241 $ 78,507 $ (4,830 ) $ — $ 133,918 Investing activities: Purchase of property and equipment (57,123 ) — — — (57,123 ) Proceeds from asset dispositions 5,236 — — — 5,236 Purchase of short-term investments (608,649 ) — — — (608,649 ) Proceeds from sale of short-term investments 505,966 — — — 505,966 Payments of deposits on aircraft (1,273 ) — — — (1,273 ) Refunds of deposits on aircraft 6,010 — — — 6,010 Net cash used in investing activities (149,833 ) — — — (149,833 ) Financing activities: Repurchase of common stock (2,448 ) — — — (2,448 ) Proceeds on line of credit 232,660 — — — 232,660 Payments on line of credit (218,160 ) — — — (218,160 ) Due to/from affiliate, net 77,535 (82,801 ) 5,266 — — Net cash provided by (used in) financing activities 89,587 (82,801 ) 5,266 — 12,052 Decrease in cash (5 ) (4,294 ) 436 — (3,863 ) Cash, beginning of year 51 5,966 253 — 6,270 Cash, end of year $ 46 $ 1,672 $ 689 $ — $ 2,407

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Consolidated Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Consolidated Accounts	PHI, INC. AND SUBSIDIARIES Schedule II – Valuation and Qualifying Consolidated Accounts (Thousands of dollars) Additions Balance at Beginning Charged to Costs and Balance at End Description of Year Expenses Deductions (1) of Year Year ended December 31, 2017: Allowance for doubtful accounts $ 6,021 $ 1,218 $ — $ 7,239 Allowance for inventory 17,305 3,570 — 20,875 Allowance for contractual discounts 111,856 480,645 474,719 117,782 Allowance for uncompensated care 46,310 78,883 72,678 52,515 Year ended December 31, 2016: Allowance for doubtful accounts $ 5,151 $ 870 $ — 6,021 Allowance for inventory 15,385 1,920 — 17,305 Allowance for contractual discounts 103,601 483,449 475,194 111,856 Allowance for uncompensated care 41,924 88,787 84,401 46,310 Year ended December 31, 2015: Allowance for doubtful accounts $ 1,351 $ 3,800 $ — 5,151 Allowance for inventory 13,517 1,868 — 15,385 Allowance for contractual discounts 96,590 439,991 432,980 103,601 Allowance for uncompensated care 41,858 84,470 84,404 41,924 (1) Deductions from provisions represent losses or expenses for which the respective provisions were created. In the case of the provision for contractual discounts and uncompensated care, such deductions are reduced by recoveries of amounts previously written off.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Nature of Operations, Basis of Consolidation, and Other General Principles	Nature of Operations, Basis of Consolidation, and Other General Principles PHI, Inc. and its subsidiaries (“PHI,” the “Company,” “we,” “us,” or “our”) provide transportation services to, from, and among offshore facilities for customers engaged in the oil and gas exploration, development, and production industry. We provide these offshore services primarily in the United States and to a lesser extent in Canada, Trinidad, Australia, New Zealand, Papua New Guinea, the Philippines, West Africa and the Middle East. We also provide air medical transportation services for hospitals and emergency service agencies, as well as aircraft maintenance and repair services to third parties in North America. The consolidated financial statements include the accounts of PHI, Inc. and its subsidiaries after the elimination of all intercompany accounts and transactions. We apply the equity method of accounting for investments in entities, if we have the ability to exercise significant influence over the operating and financial policies of the entity. We report our share of earnings or losses of equity investees in the accompanying Consolidated Statements of Operations as equity in (loss) profit of unconsolidated affiliate. At December 31, 2017 , Al A. Gonsoulin, Chairman of the Board and Chief Executive Officer, beneficially owned stock representing approximately 70.9% of the total voting power. As a result, he exercises control over the election of PHI’s directors and the outcome of matters requiring a shareholder vote.
Use of Estimates	Use of Estimates The preparation of financial statements is in conformity with accounting principles generally accepted in the United States of America (“GAAP”), which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from those estimates. Significant estimates include: Estimates of contractual allowances applicable to billings in the Air Medical segment, Inventories of spare parts, Valuation reserve related to obsolete and excess inventory, Reserves related to unpaid accounts, Depreciable lives and salvage values of property and equipment, Valuation allowance for deferred tax assets, Fair values of assets acquired and liabilities assumed, Income taxes, Healthcare insurance claims and workers’ compensation liability, and Impairment of long-lived assets.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments with maturities of three months or less , when purchased, to be cash equivalents.
Trade Receivables, net	Trade Receivables, net Trade and other receivables are stated at net realizable value. Air Medical trade receivables are presented net of allowances for contractual discounts and uncompensated care. We estimate contractual allowances and uncompensated care based on historical collection experience by payor category. The main payor categories are Medicare, Medicaid, private insurance, and self-pay. We analyze our historical payment of accounts by payor category on a monthly basis, and adjust our accounts receivable allowance based upon each category’s historical collection percentage plus any adjustments for current trends in payor behavior. Provisions for contractual discounts and uncompensated care that we applied to our Air Medical trade receivables (expressed as a percentage of total segment accounts receivable) at December 31 were as follows: 2017 2016 Allowance for contractual discounts 53% 56% Allowance for uncompensated care 24% 23%
Short-term Investments	Short-term Investments Short-term investments consist of money market funds, commercial paper, debt issued by the U.S. government or its agencies, and corporate bonds and notes, which represent funds available for current operations. In accordance with GAAP, these short-term investments are classified as available for sale. We recorded $0.3 million in net unrealized losses in 2017. These losses are reflected as a separate component of stockholders’ equity.
Inventories of Spare Parts	Inventories of Spare Parts The Company’s inventories are stated at average cost and consist primarily of spare aircraft parts. Portions of the Company’s inventories are used parts that are often exchanged with parts removed from aircraft, reworked to a useable condition according to manufacturers’ and FAA specifications, and returned to inventory. Reusable aircraft parts are included in inventory at the average cost of comparable parts. The rework costs are expensed as incurred. The Company also records an allowance for obsolete and slow-moving parts, relying principally on specific identification of such inventory. Valuation reserves related to obsolescence and slow-moving inventory were $20.9 million and $17.3 million at December 31, 2017 and 2016 , respectively.
Property and Equipment	Property and Equipment The Company records its property and equipment at cost less accumulated depreciation. For financial reporting purposes, the Company uses the straight-line method to compute depreciation based upon estimated useful lives of 5 to 15 years for flight equipment and 3 to 10 years for other equipment. Leasehold improvements are amortized over the shorter of the life of the respective asset or the term of the lease agreement and range from 6 to 10 years. The salvage value used in calculating depreciation of aircraft ranges from 25% to 54% of the aircraft’s carrying value, based upon historical aircraft sales data (historical as of 2007). The cost of scheduled inspections and modifications for flight equipment are charged to maintenance expense as incurred. We charge maintenance and repair costs to earnings as the costs are incurred. The cost of certain aircraft components are covered under contractual arrangements with the applicable aircraft manufacturer, commonly referred to as “power-by-the-hour” contracts. Under these agreements, we are charged an agreed amount per hour of flying time. The costs charged under these contractual arrangements are recognized in the period in which the flight hours occur. To the extent that we have not yet been billed for costs incurred under these arrangements, these costs are included in accrued expenses on our consolidated balance sheets. Modifications that enhance the operating performance or extend the useful lives of the aircraft are capitalized and depreciated over the remaining life of the aircraft. Upon selling or otherwise disposing of property and equipment, the Company removes the cost and accumulated depreciation from the accounts and reflects any resulting gain or loss in earnings at the time of sale or other disposition. The Company reviews its long-lived tangible assets for impairment annually, or more frequently if events or a change of circumstances indicate that an impairment may have occurred. The Company reviews certain identifiable intangibles for impairment whenever events or changes in circumstances indicate that the carrying amount of any such asset may not be recoverable. In such evaluation, the estimated future undiscounted cash flows generated by a particular asset group are compared with the book value of the asset group to determine if an impairment charge is necessary. Similar aircraft model types are grouped together for impairment testing purposes. The Company measures recoverability of assets to be held and used by comparing the carrying amount of an asset to future undiscounted net cash flows that it expects the asset to generate. When the Company determines that an asset is impaired, the Company recognizes that impairment amount, which is measured by the amount that the carrying value of the asset exceeds its fair value. In addition to the periodic review of its active long-lived tangible assets for impairment when circumstances warrant, the Company also performs a review of its parked aircraft not expected to return to service annually or whenever changes in circumstances indicate the carrying amount of an aircraft may not be recoverable. Management estimates the fair value of each aircraft not expected to return to service by considering items such as the aircraft’s age, length of time parked, likelihood of return to active service, and actual recent sales of similar aircraft. For more significant aircraft carrying values, we obtain an estimate of the fair value of the parked aircraft form third-party appraisers for use in our determination of fair value estimates. The Company records an impairment charge when the carrying value of a parked aircraft not expected to return to active service exceeds its estimated fair market value. During the twelve months ended December 31, 2017 , we sold or disposed of six medium, one fixed wing aircraft and related parts inventory utilized in our Oil and Gas segment. Cash proceeds totaled $1.3 million , resulting in a loss of $0.3 million . These aircraft no longer met our strategic needs. During the twelve months ended December 31, 2016 , we sold twelve light, eleven medium aircraft, and related parts inventory previously utilized in our Oil and Gas segment. Cash proceeds totaled $ 15.0 million , resulting in a gain of $ 3.3 million . These aircraft no longer met our strategic needs. During the twelve months ended December 31, 2015, we sold eight light and six medium aircraft previously utilized in our Oil and Gas segment. The carrying value of these assets prior to the sale was $3.7 million . These assets were sold for $3.7 million , which resulted in no gain. These aircraft no longer met our strategic needs. We also sold the associated spare parts inventory for these aircraft, which resulted in a $0.3 million loss.
Impairment Losses	Impairment Losses In connection with our normal recurring impairment testing, we recorded an impairment loss in the year ended December 31, 2017 for two light aircraft in our Oil and Gas segment. The carrying value of these aircraft was $1.8 million . Following a market analysis, we determined that the market value for these aircraft is $1.4 million (based on a Level 3 review, as defined by ASC 820, Fair Value Measurements and Disclosures). As a result of this analysis, we recorded an aggregate non-cash pre-tax impairment loss of $0.4 million for 2017 . We had $0.4 million impairment losses in the year ended December 31, 2016 . We had no impairment losses for the year ended December 31, 2015 .
Fair Value of Assets and Liabilities Acquired and Identification of Associated Goodwil and Intangible Assets	Fair Value of Assets and Liabilities Acquired and Identification of Associated Goodwill and Intangible Assets In conjunction with each acquisition we make, we must allocate the cost of the acquired entity to the assets and liabilities assumed based on their estimated fair values at the date of acquisition. As additional information becomes available, we may adjust the original estimates within a short time period subsequent to the acquisition. In addition, we are required to recognize intangible assets separately from goodwill. Determining the fair value of assets and liabilities acquired, as well as intangible assets that relate to such items as customer relationships, contracts, trade names and non-compete agreements involves professional judgment and is ultimately based on acquisition models and management’s assessment of the value of the assets acquired, and to the extent available, third party assessments. Intangible assets with finite lives are amortized over their estimated useful life as determined by management. Whenever events or changes in circumstances indicate that the carrying amount of the intangible assets may not be recoverable, the intangible assets will be reviewed for impairment. Goodwill is not amortized but instead is periodically assessed for impairment. Uncertainties associated with these estimates include fluctuations in economic obsolescence factors in the area and potential future sources of cash flow. We cannot provide assurance that actual amounts will not vary significantly from estimated amounts. Additionally, we recorded the estimated fair value of net assets acquired and liabilities assumed in connection with our acquisition of HNZ Offshore Business as of the acquisition date of December 29, 2017. The fair value measurements were primarily based on significant unobservable inputs (Level 3 as defined in Note 4) developed using company-specific information and third-party appraisals for the aircraft. See Note 2 for further information associated with the values recorded in our acquisition.
Goodwill	Goodwill Goodwill represents the amount the purchase price exceeds the fair value of net assets acquired in a business combination. Goodwill has an indefinite useful life and is not amortized, but is assessed for impairment annually or when events or changes in circumstances indicate that a potential impairment exists. Based on our assessments of the fair values of the assets we acquired and liabilities we assumed in connection with our acquisition of the HNZ Offshore Business on December 29, 2017 (discussed further in Note 2), we recognized goodwill in the fourth quarter.
Other Intangible Assets	Other Intangible Assets In connection with our acquisition of the HNZ Offshore Business, we also recognized in the fourth quarter of 2017 intangible assets for customer relationship, non-compete and tradenames. Intangible assets with finite useful lives are amortized over estimated useful lives on a straight-line basis.
Deferred Financing Costs	Deferred Financing Costs Costs incurred to obtain long-term debt financing are deferred and amortized ratably over the term of the related debt agreement.
Self-Insurance	Self-Insurance The Company maintains a self-insurance program for a portion of its healthcare costs. Self-insurance costs are accrued based upon the aggregate of the liability for reported claims and the estimated liability for claims incurred but not reported. The Company’s insurance retention was $250,000 per claim through December 31, 2017 . As of December 31, 2017 and 2016 , the Company had $1.3 million and $1.9 million , respectively, of accrued liabilities related to healthcare claims. There is also a $0.5 million deductible per incident on our workers’ compensation program. We have accrued $2.9 million and $2.5 million for the years 2017 and 2016 , respectively, related to workers’ compensation claims. The Company owns an offshore insurance company to realize savings in reinsurance costs on its insurance premiums. We paid $0.5 million and $0.6 million , respectively, to this captive company in 2017 and 2016 , which were eliminated in consolidation. The results of the captive are fully consolidated in the accompanying consolidated financial statements.
Revenue Recognition	Revenue Recognition The Company recognizes revenue related to aviation transportation services after the services are performed or the contractual obligations are met. Aircraft maintenance services revenues are recognized at the time the repair or services work is completed. Revenues related to the Company’s Air Medical segment independent provider model services are recorded net of contractual allowances under agreements with third party payors, and also recorded net of uncompensated care allowances when the services are provided. Revenues generated under the traditional provider model consist of a fixed monthly rate for aircraft availability and an hourly rate for flight time. We estimate contractual allowances and uncompensated care based on historical collection experience by payor category. The main payor categories are Medicaid, Medicare, private insurance, and self-pay. Changes in payor mix, reimbursement rates and uncompensated care rates are the factors most subject to sensitivity and variability in calculating our allowances. We compute a historical payment analysis of accounts by category. The allowance percentages calculated are applied to the payor categories, and the necessary adjustments are made to the revenue allowance. In our Air Medical Segment, the allowance for contractual discounts against outstanding accounts receivable was $117.8 million , $111.9 million , and $103.6 million as of December 31, 2017 , 2016 , and 2015 , respectively, and the allowance for uncompensated care against outstanding accounts receivable was $52.5 million , $46.3 million , and $41.9 million as of December 31, 2017 , 2016 , and 2015 , respectively. Included in the allowance for uncompensated care above is the value of services to patients who are unable to pay when it is determined that they qualify as charity care. The value of these services was $7.1 million , $8.8 million , and $9.3 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The estimated cost of providing charity services was $1.6 million , $1.9 million , and $2.0 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. The estimated costs of providing charity services are based on a calculation that applies a ratio of costs to the charges for uncompensated charity care. The ratio of costs to charges is based on the Air Medical independent provider model’s total expenses divided by gross patient service revenue. In determining the allowance estimates for our Air Medical segment’s billing, receivables and revenue, we utilize the prior twelve months’ payment history and current trends in payor behavior by each separate payor group, which we evaluate on a state by state basis. A percentage of amounts collected compared to the total invoice is determined from this process and applied to the current month’s billings and receivables. If a receivable related to the self-pay category is outstanding twelve months or greater, we record a reserve equal to 100% of the receivable. Receivables related to other payor categories are scrutinized when they are outstanding for nine months or longer and additional allowances are recorded if warranted. Provisions for contractual discounts and estimated uncompensated care that we applied to our Air Medical revenues (expressed as a percentage of total independent provider model billings) were as follows: Year Ended December 31, 2017 2016 2015 Provision for contractual discounts 66 % 67 % 65 % Provision for uncompensated care 7 % 6 % 8 % Amounts attributable to Medicaid, Medicare, private insurance, and self-pay as a percentage of net Air Medical independent provider model revenues were as follows: Year Ended December 31, 2017 2016 2015 Insurance 72 % 72 % 74 % Medicare 18 % 18 % 17 % Medicaid 9 % 9 % 8 % Self-Pay 1 % 1 % 1 % Under a contract that commenced on September 29, 2012, our Air Medical affiliate provided multiple products and services to a customer in the Middle East, including helicopter leasing, emergency medical helicopter flight services, aircraft maintenance, provision of spare parts and insurance coverage for the customer-owned aircraft, training services, and base construction. The initial contract expired in late September 2015 and was extended through September 30, 2016, when it lapsed. Each of the major deliverables mentioned above qualify as separate units of accounting under the accounting guidance for such arrangements. The selling price for each service was determined based upon third-party evidence and estimates.
Income Taxes	Income Taxes Income taxes are accounted for in accordance with the provisions of Accounting Standards Codification 740, Income Taxes . The Company provides for income taxes using the asset and liability method under which deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. The deferred tax assets and liabilities measurement uses enacted tax rates that are expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company recognizes the effect of any tax rate changes in income of the period that includes the enactment date. In connection with recording deferred income tax assets and liabilities, the Company establishes valuation allowances when necessary to reduce deferred income tax assets to amounts that it believes are more likely than not to be realized. The Company evaluates its deferred tax assets quarterly to determine whether positive or negative adjustments to its valuation allowances are appropriate in light of changes in facts or circumstances, such as changes in tax law or interactions with taxing authorities. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion of the deferred tax assets will not be realized. Adjustments to the amount of our valuation allowances can materially impact our financial condition and results of operations. The Tax Cuts and Jobs Act (the "Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35% to 21%. Following the enactment of Tax Reform Legislation in December 2017, the SEC staff issued Staff Accounting Bulletin 118 - "Income Tax Accounting Implications of the Tax Cuts and Jobs Act" (SAB 118), which provides for a measurement period of up to one year from the enactment date to complete accounting under GAAP for the tax effects of the legislation. As of December 31, 2017, the Company has not completed its accounting for the tax effects of the Act. However, the Company has remeasured its net deferred tax liability at December 31, 2017 and has provisionally recognized a net benefit of $49.2 million in its consolidated statement of operations for the year ended December 31, 2017. The Company is still analyzing certain aspects of the Act and refining its calculations, which could potentially affect the measurement of these balances or potentially give rise to changes to its current provisional estimates. The Company’s estimates may be affected by a wide variety of factors, including additional regulatory guidance issued with respect to the Act. Any adjustments to the provisional amounts will be recognized as a component of income tax in the period in which the adjustments are determined.
Earnings per Share	Earnings per Share Basic earnings per share is computed by dividing earnings (loss) during the period by the weighted average number of voting and non-voting shares outstanding during each period. Diluted earnings per share is computed by dividing net income (loss) during the period by the weighted average number of shares of common stock that would have been outstanding assuming the issuance of potentially dilutive shares of common stock, as if such shares were outstanding during the reporting period, net of shares to be repurchased using the treasury stock method. Dilutive shares for this purpose assumes restricted stock unit awards have vested.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of trade accounts receivables. Approximately 10.7% of our trade accounts receivables at December 31, 2017 were owed by an overseas customer. For a variety of reasons, the Company believes it will be paid all or substantially all of the amounts due under these receivables. Accordingly, the Company does not believe that it had significant credit risk at December 31, 2017 with respect to these overseas trade accounts receivable specifically or its aggregate trade accounts receivable generally. PHI conducts a majority of its business with major and independent oil and gas exploration and production companies with operations in the Gulf of Mexico. The Company also provides services to major medical centers. The Company continually evaluates the financial strength of its customers, but generally does not require collateral to secure its customer receivables. The Company establishes an allowance for doubtful accounts based upon factors pertaining to the credit risk of specific customers, current market conditions, and other information. Amounts are charged off as uncollectible when collection efforts have been exhausted. The allowance for doubtful accounts was $7.2 million and $6.0 million at December 31, 2017 and 2016 , respectively. Trade receivables representing amounts due pursuant to air medical independent provider model services are carried net of an allowance for estimated contractual adjustments and uncompensated care on unsettled invoices. The Company monitors its collection experience by payor category within the Air Medical segment and updates its estimated collections to be realized as deemed necessary. In our Air Medical segments, the allowance for contractual discounts was $117.8 million , $111.9 million , and $103.6 million as of December 31, 2017 , 2016 , and 2015 , respectively, and the allowance for uncompensated care was $52.5 million , $46.3 million , and $41.9 million as of December 31, 2017 , 2016 , and 2015 , respectively. The Company’s two largest oil and gas customers accounted for 23% of consolidated operating revenues for the year ended December 31, 2017 , 24% for the year ended December 31, 2016 , and 26% for the year ended December 31, 2015 . The Company also carried accounts receivable from these same customers totaling 16% and 16% of net trade receivables on December 31, 2017 and 2016 , respectively. The customer base of our Air Medical and Technical Services operations has traditionally been less concentrated than the customer base of our Oil and Gas operations. Over the past three years, none of our current Air Medical or Technical Services customers accounted for more than 2% of our consolidated operating revenues. One of our former Air Medical customers, however, did account for 5% and 9% of our consolidated operating revenues for 2016 and 2015, respectively. The Company also carried accounts receivable from its largest customer totaling 10% and 13% of net trade receivables on December 31, 2017 and 2016 , respectively. Substantially all of the Company’s cash is maintained in one financial institution in amounts that typically exceed federally insured limits. The Company has not experienced any losses in such accounts and based on current circumstances does not believe that it is exposed to significant credit risk.
Foreign Currency Translation	Foreign Currency Translation Our consolidated financial statements are reported in U.S. dollars. Our foreign subsidiaries maintain their records primarily in the currency of the country in which they operate. Assets and liabilities of foreign subsidiaries in non-highly inflationary economies are translated into U.S. dollars using rates of exchange at the balance sheet date. Translation adjustments are recorded in other comprehensive income (loss). Revenues and expenses are translated at rates of exchange in effect during the year. Transaction gains and losses are recorded in net earnings (loss).
New Accounting Pronouncements	New Accounting Pronouncements On January 26, 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350) : Simplifying the Test for Goodwill Impairment (ASU 2017-04). ASU 2017-04 removes the requirement to compare the implied fair value of goodwill with the carrying amount as part of Step 2 of the goodwill impairment test. Under the new standard, the goodwill impairment loss will be measured as the excess of a reporting unit's carrying amount over its fair value, not exceeding the total amount of goodwill allocated to that reporting unit, which may increase the frequency of goodwill impairment charges if a future goodwill impairment test does not pass the Step 1 evaluation. ASU 2017-04 is effective prospectively for periods beginning on or after December 15, 2019, with early adoption permitted. The Company adopted ASU 2017-04 effective January 1, 2018. The Company will perform goodwill impairment test under the new standard in 2018. Effective January 1, 2017, we adopted Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718) : Improvements to Employee Share-Based Payment Accounting, which was issued by the Financial Accounting Standards Board (“FASB”) in March 2016. This new standard requires that excess tax benefits and deficiencies resulting from stock-based compensation awards vesting and exercises be recognized in the income statement. Previously, these amounts were recognized in additional paid-in capital. As a result, during the first quarter of 2017 we recorded a cumulative-effect adjustment of $1.0 million increasing retained earnings and decreasing deferred tax liability on our balance sheet dated December 31, 2017. Accordingly, we recorded income tax expense of $0.9 million in our consolidated statement of operations for the year ended December 31, 2017, in recognition of excess tax deficiencies related to equity compensation. Under this new standard, the corresponding cash flows are now reflected in cash provided by operating activities instead of financing activities, as was previously required. In 2014, the FASB issued ASC 606, Revenue from Contracts with Customers (ASC 606), replacing the existing accounting standard and industry specific guidance for revenue recognition with a five-step model for recognizing and measuring revenue from contracts with customers. The underlying principle of the new standard is to recognize revenue to depict the transfer of goods or services to customers at the amount expected to be collected. The new standard also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenue and the related cash flows arising from contracts with customers. The Company has completed the evaluation of all revenue streams and determined that the adoption of ASC 606 will not change the current timing of revenue recognition for such transactions. Entities can transition to the standard either retrospectively or as a cumulative effect adjustment as of the date of adoption. The new standard is effective for the Company beginning on January 1, 2018. We adopted this standard on January 1, 2018 utilizing the modified retrospective method. Under the modified retrospective method of adoption, prior year reported results are not recast; however, a cumulative-effect adjustment to retained earnings at January 1, 2018 is recorded. In addition, quarterly disclosures will include comparative information on 2018 financial statement line items under current guidance. To the extent applicable, upon adoption, we may be required to comply with expanded disclosure requirements, including the disaggregation of revenues to depict the nature and uncertainty of types of revenues, contract assets and liabilities, performance obligations, significant judgments and estimates affecting the amount and timing of revenue recognition, and determination of transaction prices. The adoption of ASC 606 did not result in a cumulative-effect adjustment. Revenues in our Oil and Gas segment and Air Medical segment hospital contracts are primarily comprised of a fixed monthly fee for a particular model of aircraft, plus a variable component based on flight time. Under the independent provider programs of our Air Medical segment, our revenues are based on a flat rate plus a variable charge per patient-loaded mile, and are recorded net of contractual allowances. We also generate revenue on a cost-plus basis in our Technical Services segment. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes , which requires that deferred tax assets and liabilities be classified as noncurrent in a classified balance sheet. PHI, Inc. adopted this ASU in the fourth quarter of 2017 on a prospective basis. Beginning with the December 31, 2017 balances, all deferred taxes will be classified as non-current. Periods prior to December 31, 2017 were not retrospectively adjusted. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other than Inventory , which will require an entity to recognize the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. The ASU is effective for annual periods beginning after December 15, 2017, including interim periods within those annual periods. We do not expect that the adoption of this ASU will have a material impact on our consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases , which replaces the existing guidance on leasing transactions in ASC 840 to require recognition of the assets and liabilities for the rights and obligations created by those leases on the balance sheet. We are currently evaluating the effects of this standard, and expect the adoption of this standard will result in a material change to our consolidated assets and liabilities based on our lease portfolio as of December 31, 2017. We plan to adopt this standard beginning January 1, 2019.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Provisions for Contractual Discounts and Uncompensated Care Applied to Air Medical Trade Receivables Expressed as Percentage of Total Segment Accounts Receivable	Provisions for contractual discounts and uncompensated care that we applied to our Air Medical trade receivables (expressed as a percentage of total segment accounts receivable) at December 31 were as follows: 2017 2016 Allowance for contractual discounts 53% 56% Allowance for uncompensated care 24% 23%
Schedule of Goodwill	The following table summarizes recent activity regarding the Company's goodwill (in thousands): Oil & Gas Air Medical Technical Services Total Balance December 31, 2016 — — — — Acquisition Activities 61,299 — — 61,299 Balance December 31, 2017 61,299 — — 61,299
Schedule of Intangible Assets	Intangible assets with finite useful lives are amortized over estimated useful lives on a straight-line basis. Our intangible assets by types consist of the following (in thousands): Estimated Useful Lives Gross Amount Accumulated Amortization Net Balance Customer Relationship 15 11,622 — 11,622 Non-Compete Agreements 5 900 — 900 Tradenames 7 4,201 — 4,201 Total 16,723 — 16,723
Schedule of Provisions for Contractual Discounts and Estimated Uncompensated Care Applied to Air Medical Revenues Expressed as Percentage of Total Independent Provider Model Billings	Provisions for contractual discounts and estimated uncompensated care that we applied to our Air Medical revenues (expressed as a percentage of total independent provider model billings) were as follows: Year Ended December 31, 2017 2016 2015 Provision for contractual discounts 66 % 67 % 65 % Provision for uncompensated care 7 % 6 % 8 %
Schedule of Net Revenue Attributable to Medicaid, Medicare, Private Insurance and Self Pay as Percentage of Net Air Medical Independent Provider Model Revenues	Amounts attributable to Medicaid, Medicare, private insurance, and self-pay as a percentage of net Air Medical independent provider model revenues were as follows: Year Ended December 31, 2017 2016 2015 Insurance 72 % 72 % 74 % Medicare 18 % 18 % 17 % Medicaid 9 % 9 % 8 % Self-Pay 1 % 1 % 1 %

Acquisition of Business (Tables

Acquisition of Business (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Fair Value of Assets Acquired and Liabilities Assumed	The following amounts represent the fair value of assets acquired and liabilities assumed in the merger. Thousands of dollars Cash $ 4,142 Accounts receivable 27,819 Inventories 3,096 Fixed assets 43,689 Intangible assets: Noncompete agreements (weighted-average life of 5 years) 900 Customer relationships (weighted-average life of 15 years) 11,622 Tradenames (weighted-average life of 7 years) 4,201 Other assets 5,310 Accounts payable and accrued liabilities (25,272 ) Deferred taxes (1) (5,270 ) Other liabilities (750 ) Total identifiable net assets 69,487 Goodwill (2) 61,299 Total consideration transferred $ 130,786 (1) In connection with the acquisition accounting, PHI provided deferred taxes related to the estimated fair value adjustments for acquired intangible assets. (2) Goodwill is the excess of purchase price over fair market value of the net assets acquired under the acquisition method of accounting. The amount of goodwill that is deductible for income tax purposes is not significant.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Components of Investments	Investments consisted of the following as of December 31, 2017 : Cost Basis Unrealized Gains Unrealized Losses Fair Value (Thousands of dollars) Investments: Money market mutual funds $ 5,601 $ — $ — $ 5,601 Commercial paper — — — — U.S. government agencies 7,501 — (34 ) 7,467 Corporate bonds and notes 63,880 — (330 ) 63,550 Subtotal 76,982 — (364 ) 76,618 Deferred compensation plan assets included in other assets 2,685 — — 2,685 Total $ 79,667 $ — $ (364 ) $ 79,303 Investments consisted of the following as of December 31, 2016 : Cost Basis Unrealized Gains Unrealized Losses Fair Value (Thousands of dollars) Investments: Money market mutual funds $ 18,118 $ — $ — $ 18,118 Commercial paper 27,906 — (39 ) 27,867 U.S. government agencies 13,295 — (32 ) 13,263 Corporate bonds and notes 244,202 2 (622 ) 243,582 Subtotal 303,521 2 (693 ) 302,830 Deferred compensation plan assets included in other assets 2,394 — — 2,394 Total $ 305,915 $ 2 $ (693 ) $ 305,224
Cost and Fair Value of Debt Investments Based on Maturities	The following table presents the cost and fair value of our debt investments based on maturities as of December 31, 2017 2016 Amortized Costs Fair Value Amortized Costs Fair Value (Thousands of dollars) Due in one year or less $ 31,348 $ 31,254 $ 184,587 $ 184,334 Due within two years 40,032 39,763 100,816 100,378 Total $ 71,380 $ 71,017 $ 285,403 $ 284,712
Average Coupon Rate Percentage and Average Days to Maturity of Debt	The following table presents the average coupon rate percentage and the average days to maturity of our debt investments as of December 31, 2017 2016 Average Coupon Rate (%) Average Days To Maturity Average Coupon Rate (%) Average Days To Maturity Commercial paper — 0 1.001 184 U.S. government agencies 1.370 370 0.970 400 Corporate bonds and notes 1.766 392 1.745 318
Investments in Continuous Unrealized Loss Position for Less Than Twelve Months	The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for less than twelve months as of December 31, 2017 2016 Fair Value Unrealized Losses Fair Value Unrealized Losses (Thousands of dollars) Commercial paper $ — $ — $ 27,867 $ (39 ) U.S. government agencies 5,472 (28 ) 13,263 (32 ) Corporate bonds and notes 44,069 (271 ) 210,836 (602 ) Total $ 49,541 $ (299 ) $ 251,966 $ (673 )
Investments in Continuous Unrealized Loss Position For Twelve Months Or More	The following table presents the fair value and unrealized losses related to our investments that have been in a continuous unrealized loss position for twelve months or more as of December 31, 2017 2016 Fair Value Unrealized Losses Fair Value Unrealized Losses (Thousands of dollars) U.S. government agencies $ 1,994 $ (6 ) $ — $ — Corporate bonds and notes $ 19,482 $ (59 ) $ 24,196 $ (20 ) Total $ 21,476 $ (65 ) $ 24,196 $ (20 )

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Summary of Valuation of Investments and Financial Instruments Pricing Levels	The following tables summarize the valuation of our investments and financial instruments by the above pricing levels as of the valuation dates listed: December 31, 2017 Total (Level 1) (Level 2) (Thousands of dollars) Investments: Money market mutual funds $ 5,601 $ 5,601 $ — Commercial paper — — — U.S. government agencies 7,467 — 7,467 Corporate bonds and notes 63,550 — 63,550 76,618 5,601 71,017 Deferred compensation plan assets 2,685 2,685 Total $ 79,303 $ 8,286 $ 71,017 December 31, 2016 Total (Level 1) (Level 2) (Thousands of dollars) Investments: Money market mutual funds $ 18,118 $ 18,118 $ — Commercial paper 27,867 — 27,867 U.S. government agencies 13,263 — 13,263 Corporate bonds and notes 243,582 — 243,582 302,830 18,118 284,712 Deferred compensation plan assets 2,394 2,394 — Total $ 305,224 $ 20,512 $ 284,712
Summary of Combined Fair Value of Assets that Incurred Impairments	The below table summarizes the combined fair value of the assets that incurred impairments during the years ended December 31, 2017 , 2016 and 2015 , along with the amount of the impairment. The impairment charges were recorded in Impairment of assets. See Note 1 for additional information. Year Ended December 31, 2017 2016 2015 (Thousands of dollars) Amount of impairment incurred $ 368 $ 407 $ — Combined fair value of assets incurring impairment, after impairment charges $ 1,380 $ 1,380 $ —

Property and Equipment (Tables)

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

Other Assets (Tables)

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

Accrued and Other Current Lia33

Accrued and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued and other current liabilities as of December 31 consisted of the following: 2017 2016 (Thousands of dollars) Salaries & wages $ 6,240 $ 5,949 Incentive compensation 8,991 1,576 Income taxes 930 587 Interest 8,108 8,057 Vacation payable 7,619 5,700 Group medical 1,344 1,892 Transportations tax 971 427 Operating lease 710 769 Workers compensation 959 865 Other 5,978 2,524 Total accrued liabilities $ 41,850 $ 28,346

Long Term Debt (Tables)

Long Term Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Components of Long-term Debt	The components of long-term debt as of December 31 were as follows: December 31, 2017 December 31, 2016 Principal Unamortized Debt Issuance Debt Cost Principal Unamortized Debt Issuance Debt Cost (Thousands of dollars) Senior Notes issued March 17, 2014, interest only payable semi-annually at 5.25%, maturing March 15, 2019 $ 500,000 $ 1,506 $ 500,000 $ 2,753 Revolving Credit Facility due March 7, 2019 with a group of commercial banks, interest payable at variable rates 117,500 — 134,000 — Total long-term debt $ 617,500 $ 1,506 $ 634,000 $ 2,753
Summary of Annual Maturities of Long-term Debt	Listed below is information on our future annual maturities of long-term debt (in thousands): 2018 $ — 2019 617,500 2020 — 2021 — 2022 — Thereafter — Total $ 617,500

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	For financial reporting purposes, (loss) earnings before income taxes includes the following components: Year Ended December 31, 2017 2016 2015 (Thousands of dollars) United States $ (50,871 ) $ (25,604 ) $ 45,038 Foreign (570 ) (1,546 ) (1,782 ) Total (51,441 ) (27,149 ) 43,256
Schedule of Income Tax Expense	The provision for income taxes for 2017, 2016, and 2015 consisted of the following: Year Ended December 31, 2017 2016 2015 (Thousands of dollars) U.S. Federal: Current $ — $ — $ — Deferred (57,637 ) (5,488 ) 13,629 (57,637 ) (5,488 ) 13,629 U.S. State: Current $ 199 $ 427 $ 284 Deferred $ (717 ) $ 3,218 $ (740 ) $ (518 ) $ 3,645 $ (456 ) Foreign: Current $ 108 $ 1,374 $ 3,159 Deferred $ (926 ) — — $ (818 ) $ 1,374 $ 3,159 Provision for income taxes $ (58,973 ) $ (469 ) $ 16,332
Schedule of Income Tax Expense as Percentage of Pre-Tax Earnings	Income tax expense as a percentage of pre-tax earnings varies from the effective Federal statutory rate of 35% as a result of the following: Year Ended Year Ended Year Ended (Thousands of dollars, except percentage amounts) Amount Tax Amount Tax Amount Tax Income taxes at statutory rate $ (18,004 ) 35 $ (9,502 ) 35 $ 15,140 35 Increase (decrease) in taxes resulting from: Valuation allowance on foreign tax credits 6,145 (12 ) 8,991 (33 ) — — Valuation allowance on state net operating loss carryforwards 868 (2 ) 5,028 (19 ) — — Valuation allowance reversal–investment in foreign entity — — — (456 ) (1 ) Valuation Allowance - Other 1,353 (3 ) — — — — Change in tax rate on deferred items — — (4,772 ) 18 1,078 3 % Tax reform – Impact of change in tax rate (49,219 ) 96 — — — — State income taxes, net of federal benefit (1,386 ) 3 (1,384 ) 5 146 — Other items – net 1,270 (2 ) 1,170 (4 ) 424 1 Total $ (58,973 ) 115 $ (469 ) 2 $ 16,332 38
Schedule of Tax Effects of Temporary Differences that Give Rise to Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities	The tax effects of significant items comprising our net deferred tax balance at December 31 are as follows: 2017 2016 (Thousands of dollars) Deferred tax assets: Deferred compensation $ 626 $ 937 Foreign tax credits 19,453 21,492 Vacation and bonus accrual 3,936 1,674 Inventory valuation 4,954 7,655 Rental accrual 747 1,416 Hurricane relief credit 1,255 1,255 Stock-based compensation 988 2,202 Other 2,235 3,115 Net operating losses 82,044 89,256 Total deferred tax assets 116,238 129,002 Valuation allowance – state NOL carryforwards (5,998 ) (5,318 ) Valuation allowance – tax credit carryforwards (16,537 ) (11,039 ) Valuation allowance – foreign NOL carryforwards (98 ) — Total deferred tax assets, net 93,605 112,645 Deferred tax liabilities: Tax depreciation in excess of book depreciation (171,116 ) (253,560 ) Other (5,185 ) — Total deferred tax liabilities (176,301 ) (253,560 ) Net deferred tax liabilities $ (82,696 ) $ (140,915 ) Deferred tax assets – short-term — 10,798 Deferred tax assets – long-term 3,309 — Deferred tax liability – long-term (86,005 ) (151,713 ) Net deferred tax liabilities $ (82,696 ) $ (140,915 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Components of Basic and Diluted Earnings Per Share	The components of basic and diluted earnings per share for the years ended December 31, are as follows: 2017 2016 2015 (in thousands) Weighted average outstanding shares of common stock, basic 15,762 15,663 15,566 Dilutive effect of unvested restricted stock units — — 76 Weighted average outstanding shares of common stock, diluted 15,762 15,663 15,642

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Activity for Non-voting Time-vested Restricted Stock	The following table summarizes the activity for non-voting time-vested restricted stock units granted to non-employee directors for the year ended December 31, 2017 . Share Units Weighted Average Grant-Date Fair Value Remaining Average Contractual Life (in years) Aggregate Value (in thousands) Outstanding at January 1, 2017 11,559 $ 23.01 2.13 $ 266 Granted 10,323 11.91 Forfeited — — Vested and released to participants (2,202 ) 44.04 Outstanding at December 31, 2017 19,680 $ 14.94 2.71 $ 292
Non-Voting Time-Vested Restricted Stock Units [Member]
Summary of Activity for Non-voting Time-vested Restricted Stock	The following table summarizes the activity for non-voting time-vested restricted stock units granted to employees for the year ended December 31, 2017 . Share Units Weighted Average Grant-Date Fair Value Remaining Average Contractual Life ( in years) Aggregate Value ( in thousands) Outstanding at January 1, 2017 202,560 $ 37.91 1.25 $ 7,679 Granted 480,065 11.42 Forfeited (10,211 ) 10.01 Vested and released to participants (137,703 ) 41.76 Outstanding at December 31, 2017 534,711 $ 12.80 2.26 $ 6,844
Non-Voting Performance Based Restricted Stock Units [Member]
Summary of Activity for Non-voting Time-vested Restricted Stock	The following table summarizes the activity for non-voting performance-based restricted stock units for the year ended December 31, 2017 . Share Units Weighted Average Grant-Date Fair Value Remaining Average Contractual Life ( in years) Aggregate Value ( in thousands) Outstanding at January 1, 2017 569,418 $ 25.83 1.19 $ 14,708 Granted 371,045 15.11 Forfeited (122,313 ) 41.64 Vested and released to participants — — Outstanding at December 31, 2017 818,150 $ 18.60 1.20 $ 15,218

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Summary of Rental Expense Incurred under Leases	Rental expense incurred under these leases consisted of the following: Year Ended Year Ended Year Ended (Thousands of dollars) Aircraft $ 39,815 $ 44,130 $ 45,360 Other 9,504 9,451 8,358 Total $ 49,319 $ 53,581 $ 53,718
Summary of Remaining Aggregate Lease Commitments Under Operating Leases Having Initial Non-Cancelable Terms in Excess of One Year	The table includes renewal periods on the principal operating facility lease. Aircraft Other Total (Thousands of dollars) 2018 $ 35,723 $ 5,157 $ 40,880 2019 31,245 3,670 34,915 2020 27,406 3,308 30,714 2021 27,272 2,468 29,740 2022 26,758 1,153 27,911 Thereafter 29,077 9,832 38,909 $ 177,481 $ 25,588 $ 203,069

Business Segments and Geograp39

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

Quarterly Financial Data (Una40

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of Condensed Quarterly Results of Operations	The condensed quarterly results of operations for the years ended December 31, 2017 and 2016 (in thousands of dollars, except per share data) were as follows: Quarter Ended March 31, June 30, September 30, December 31, 2017 2017 2017 2017 (Thousands of dollars, except per share data) Operating revenues, net $ 134,618 $ 146,424 $ 150,167 $ 148,336 (Loss) gain on disposition of assets, net — 7 4 287 (Loss) earnings before income taxes (23,073 ) (3,150 ) (4,899 ) (20,319 ) Net (loss) earnings (15,248 ) (3,273 ) (3,277 ) 29,330 Net (loss) earnings per share Basic (0.97 ) (0.21 ) (0.21 ) 1.87 Diluted (0.97 ) (0.21 ) (0.21 ) 1.87 Quarter Ended March 31, June 30, September 30, December 31, 2016 2016 2016 2016 (Thousands of dollars, except per share data) Operating revenues, net $ 164,016 $ 167,136 $ 158,093 $ 144,853 Gain (loss) on disposition of assets, net (359 ) 4,298 (85 ) (504 ) Earnings before income taxes (7,488 ) 117 (7,766 ) (12,012 ) Net earnings (8,932 ) 4,277 (4,967 ) (17,058 ) Net earnings per share Basic (0.57 ) 0.27 (0.32 ) (1.08 ) Diluted (0.57 ) 0.27 (0.32 ) (1.08 )

Condensed Consolidating Finan41

Condensed Consolidating Financial Information - Guarantor Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Consolidating Balance Sheets	PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS (Thousands of dollars) December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated ASSETS Current Assets: Cash $ 47 $ 1,072 $ 7,651 $ — $ 8,770 Short-term investments 64,237 — — — 64,237 Accounts receivable – net 90,077 74,886 38,020 (17,004 ) 185,979 Intercompany receivable — 126,366 — (126,366 ) — Inventories of spare parts – net 68,737 9,049 3,095 — 80,881 Prepaid expenses 8,348 1,898 1,229 — 11,475 Deferred income taxes — — — — — Income taxes receivable 345 9 917 — 1,271 Total current assets 231,791 213,280 50,912 (143,370 ) 352,613 Investment in subsidiaries and others 397,301 — — (397,301 ) — Property and equipment – net 617,488 284,984 44,293 — 946,765 Restricted cash and investments 12,382 — 14 — 12,396 Other assets 139,754 908 (131,921 ) — $ 8,741 Deferred income tax — — 3,309 — 3,309 Goodwill — — 61,299 — $ 61,299 Intangible assets — — 16,723 — 16,723 Total assets $ 1,398,716 $ 499,172 $ 44,629 $ (540,671 ) $ 1,401,846 LIABILITIES AND SHAREHOLDERS’ EQUITY Current Liabilities: Accounts payable $ 28,130 $ 4,636 $ 21,425 $ (17,005 ) $ 37,186 Accrued and other current liabilities 23,147 10,577 8,126 — 41,850 Intercompany payable 113,387 — 12,978 (126,365 ) — Total current liabilities 164,664 15,213 42,529 (143,370 ) 79,036 Long-term debt 615,994 — — — 615,994 Deferred income taxes and other long-term liabilities 5,404 84,300 4,458 — 94,162 Shareholders’ Equity: Common stock and paid-in capital 309,933 77,951 1,375 (79,326 ) 309,933 Accumulated other comprehensive loss (280 ) — — — (280 ) Retained earnings 303,001 321,708 (3,733 ) (317,975 ) 303,001 Total shareholders’ equity 612,654 399,659 (2,358 ) (397,301 ) 612,654 Total liabilities and shareholders’ equity $ 1,398,716 $ 499,172 $ 44,629 $ (540,671 ) $ 1,401,846 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS (Thousands of dollars) December 31, 2016 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated ASSETS Current Assets: Cash $ 36 $ 2,100 $ 460 $ — $ 2,596 Short-term investments 289,806 — — — 289,806 Accounts receivable – net 71,458 62,868 3,939 — 138,265 Intercompany receivable — 91,040 (33,136 ) (57,904 ) — Inventories of spare parts – net 61,834 8,568 — — 70,402 Prepaid expenses 6,990 2,184 85 — 9,259 Deferred income taxes 10,798 — — — 10,798 Income taxes receivable 558 (18 ) — — 540 Total current assets 441,480 166,742 (28,652 ) (57,904 ) 521,666 Investment in subsidiaries 353,160 — — (353,160 ) — Property and equipment – net 589,104 294,197 20,676 — 903,977 Restricted investments 13,023 — 15 — 13,038 Other assets 8,660 1,099 — — 9,759 Total assets $ 1,405,427 $ 462,038 $ (7,961 ) $ (411,064 ) $ 1,448,440 LIABILITIES AND SHAREHOLDERS’ EQUITY Current Liabilities: Accounts payable $ 22,744 $ 5,822 $ 138 $ — $ 28,704 Accrued liabilities 18,725 9,418 203 — 28,346 Intercompany payable 57,904 — — (57,904 ) — Total current liabilities 99,373 15,240 341 (57,904 ) 57,050 Long-term debt 631,247 — — — 631,247 Deferred income taxes and other long-term liabilities 75,029 85,336 — — 160,365 Shareholders’ Equity: Common stock and paid-in capital 305,815 77,951 1,240 (79,191 ) 305,815 Accumulated other comprehensive loss (478 ) — — — (478 ) Retained earnings 294,441 283,511 (9,542 ) (273,969 ) 294,441 Total shareholders’ equity 599,778 361,462 (8,302 ) (353,160 ) 599,778 Total liabilities and shareholders’ equity $ 1,405,427 $ 462,038 $ (7,961 ) $ (411,064 ) $ 1,448,440
Condensed Consolidating Statements of Operations	PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Thousands of dollars) For the year ended December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Operating revenues, net $ 310,449 $ 262,229 $ 23,871 $ (17,004 ) $ 579,545 Expenses: Direct expenses 326,152 212,691 24,860 (17,004 ) 546,699 Selling, general, and administrative expenses 41,134 12,462 221 — 53,817 Total operating expenses 367,286 225,153 25,081 (17,004 ) 600,516 Loss on disposition of assets, net 300 (2 ) — — 298 Impairment of assets 368 — — — 368 Equity in loss of unconsolidated affiliate 1,021 — (636 ) — 385 Operating (loss) income (58,526 ) 37,078 (574 ) — (22,022 ) Equity in net earnings of consolidated subsidiaries (38,553 ) — — 38,553 — Interest expense 32,161 22 — — 32,183 Other income, net (2,757 ) (2 ) (5 ) — (2,764 ) (9,149 ) 20 (5 ) 38,553 29,419 (Loss) earnings before income taxes (49,377 ) 37,058 (569 ) (38,553 ) (51,441 ) Income tax (benefit) expense (56,909 ) (1,138 ) (926 ) — (58,973 ) Net earnings (loss) $ 7,532 $ 38,196 $ 357 $ (38,553 ) $ 7,532 For the year ended December 31, 2016 Parent Non- Company Guarantor Guarantor Only (issuer) Subsidiaries Subsidiaries Eliminations Consolidated Operating revenues, net $ 339,829 $ 293,329 $ 940 $ — $ 634,098 Expenses: Direct expenses 347,532 237,635 7,383 — 592,550 Selling, general, and administrative expenses 32,911 10,984 541 (18 ) 44,418 Total operating expenses 380,443 248,619 7,924 (18 ) 636,968 Gain on disposition of assets, net (3,350 ) — — — (3,350 ) Impairment of assets 407 — — — 407 Equity in profit of unconsolidated affiliate (151 ) — — — (151 ) Operating (loss) income (37,520 ) 44,710 (6,984 ) 18 224 Equity in net earnings of consolidated subsidiaries (22,182 ) — — 22,182 — Interest expense 30,585 46 13 — 30,644 Other income, net (3,284 ) (5 ) — 18 (3,271 ) 5,119 41 13 22,200 27,373 (Loss) earnings before income taxes (42,639 ) 44,669 (6,997 ) (22,182 ) (27,149 ) Income tax (benefit) expense (15,959 ) 15,490 — — (469 ) Net (loss) earnings $ (26,680 ) $ 29,179 $ (6,997 ) $ (22,182 ) $ (26,680 ) PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Thousands of dollars) For the year ended December 31, 2015 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Operating revenues, net $ 476,969 $ 327,259 $ — $ — $ 804,228 Expenses: Direct expenses 426,239 259,198 1,631 (18 ) 687,050 Selling, general, and administrative expenses 35,694 10,577 151 — 46,422 Total operating expenses 461,933 269,775 1,782 (18 ) 733,472 Loss on disposition of assets, net 339 — — 339 Equity in loss of unconsolidated affiliate 306 — — 306 Operating income 14,391 57,484 (1,782 ) 18 70,111 Equity in net earnings of consolidated subsidiaries (31,225 ) — — 31,225 — Interest expense 28,946 120 — — 29,066 Other income, net (2,222 ) (7 ) — 18 (2,211 ) (4,501 ) 113 — 31,243 26,855 Earnings before income taxes 18,892 57,371 (1,782 ) (31,225 ) 43,256 Income tax (benefit) expense (8,032 ) (24,364 ) — — 16,332 Net earnings $ 26,924 $ 33,007 $ (1,782 ) $ (31,225 ) $ 26,924
Condensed Consolidated Statements of Comprehensive Income	PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME (Thousands of dollars) For the year ended December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Net earnings $ 7,532 $ 38,196 $ 357 $ (38,553 ) $ 7,532 Unrealized gain on short-term investments 310 — — — 310 Changes in pension plan assets and benefit obligations (3 ) — — — (3 ) Tax effect (109 ) — — — (109 ) Total comprehensive income $ 7,730 $ 38,196 $ 357 $ (38,553 ) $ 7,730 For the year ended December 31, 2016 Parent Non- Company Guarantor Guarantor Only Subsidiaries Subsidiaries Eliminations Consolidated Net (loss) earnings $ (26,680 ) $ 29,179 $ (6,997 ) $ (22,182 ) $ (26,680 ) Unrealized gain on short-term investments 241 — — — 241 Changes in pension plan assets and benefit obligations (39 ) — — — (39 ) Tax effect (113 ) — — — (113 ) Total comprehensive (loss) income $ (26,591 ) $ 29,179 $ (6,997 ) $ (22,182 ) $ (26,591 ) For the year ended December 31, 2015 Parent Non- Company Guarantor Guarantor Only Subsidiaries Subsidiaries Eliminations Consolidated Net earnings $ 26,924 $ 33,007 $ (1,782 ) $ (31,225 ) $ 26,924 Unrealized loss on short-term investments (641 ) — — — (641 ) Other unrealized gain 24 — — — 24 Changes in pension plan assets and benefit obligations 7 — — — 7 Tax effect 254 — — — 254 Total comprehensive income $ 26,568 $ 33,007 $ (1,782 ) $ (31,225 ) $ 26,568
Condensed Consolidating Statements of Cash Flows	PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (Thousands of dollars) For the year ended December 31, 2017 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Net cash (used in) provided by operating activities $ (62,581 ) $ 40,628 $ 2,850 $ — $ (19,103 ) Investing activities: Purchase of property and equipment (56,757 ) — — — (56,757 ) Proceeds from asset dispositions 1,296 — — — 1,296 Purchase of short-term investments (637,980 ) — — — (637,980 ) Proceeds from sale of short-term investments 862,942 — — — 862,942 Payments of deposits on aircraft — — — — — Loan to unconsolidated affiliate — — — — — Loan to third party (824 ) — — — (824 ) Business acquisitions and investments, net of cash (130,788 ) — 4,144 — (126,644 ) Net cash provided by investing activities 37,889 — 4,144 — 42,033 Financing activities: Repurchase of common stock (256 ) — — — (256 ) Proceeds on line of credit 152,150 — — — 152,150 Payments on line of credit (168,650 ) — — — (168,650 ) Due to/from affiliate, net 41,459 (41,656 ) 197 — — Net cash (used in) provided by financing activities 24,703 (41,656 ) 197 — (16,756 ) Increase (decrease) in cash 11 (1,028 ) 7,191 — 6,174 Cash, beginning of year 36 2,100 460 — 2,596 Cash, end of year $ 47 $ 1,072 $ 7,651 $ — $ 8,770 (1) Net of the effect of business acquisitions. PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (Thousands of dollars) For the year ended December 31, 2016 Parent Guarantor Non-Guarantor Subsidiaries Eliminations Consolidated Net cash (used in) by operating activities $ (46,738 ) $ 52,873 $ (6,699 ) $ — $ (564 ) Investing activities: Purchase of property and equipment (81,484 ) — (358 ) — (81,842 ) Proceeds from asset dispositions 14,983 — — — 14,983 Purchase of short-term investments (321,453 ) — — — (321,453 ) Proceeds from sale of short-term investments 316,543 — — — 316,543 Payments of deposits on aircraft (2,249 ) — — — (2,249 ) Loan to unconsolidated affiliate (1,200 ) — — — (1,200 ) Net cash used in investing activities (74,860 ) — (358 ) — (75,218 ) Financing activities: Repurchase of common stock (529 ) — — — (529 ) Proceeds on line of credit 264,700 — — — 264,700 Payments on line of credit (188,200 ) — — — (188,200 ) Due to/from affiliate, net 45,617 (52,445 ) 6,828 — — Net cash provided by (used in) financing activities 121,588 (52,445 ) 6,828 — 75,971 (Decrease) increase in cash (10 ) 428 (229 ) — 189 Cash, beginning of year 46 1,672 689 — 2,407 Cash, end of year $ 36 $ 2,100 $ 460 $ — $ 2,596 PHI, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (Thousands of dollars) For the year ended December 31, 2015 Parent Guarantor Non- Eliminations Consolidated Net cash provided by operating activities $ 60,241 $ 78,507 $ (4,830 ) $ — $ 133,918 Investing activities: Purchase of property and equipment (57,123 ) — — — (57,123 ) Proceeds from asset dispositions 5,236 — — — 5,236 Purchase of short-term investments (608,649 ) — — — (608,649 ) Proceeds from sale of short-term investments 505,966 — — — 505,966 Payments of deposits on aircraft (1,273 ) — — — (1,273 ) Refunds of deposits on aircraft 6,010 — — — 6,010 Net cash used in investing activities (149,833 ) — — — (149,833 ) Financing activities: Repurchase of common stock (2,448 ) — — — (2,448 ) Proceeds on line of credit 232,660 — — — 232,660 Payments on line of credit (218,160 ) — — — (218,160 ) Due to/from affiliate, net 77,535 (82,801 ) 5,266 — — Net cash provided by (used in) financing activities 89,587 (82,801 ) 5,266 — 12,052 Decrease in cash (5 ) (4,294 ) 436 — (3,863 ) Cash, beginning of year 51 5,966 253 — 6,270 Cash, end of year $ 46 $ 1,672 $ 689 $ — $ 2,407

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)Aircraft	Dec. 31, 2016USD ($)Aircraft	Dec. 31, 2015USD ($)Aircraft
Summary Of Significant Accounting Policies [Line Items]
Percentage of stock owned by CEO	70.90%
Maturities Period of liquid investments	Three months or less
Valuation reserves related to obsolescence and slow moving inventory	$ 20,900,000	$ 17,300,000
Property and equipment – net	946,765,000	903,977,000
Impairments of assets	368,000	407,000	$ 0
Insurance retention per claim	250,000
Accrued liabilities related to health care claims	1,300,000	1,900,000
Amount deductible per incident	500,000
Accrued expense related to workers compensation claims	2,900,000	2,500,000
Amounts paid to offshore insurance captive	500,000	600,000
Allowance for contractual discounts against outstanding accounts receivable	117,800,000	111,900,000	103,600,000
Allowance for uncompensated care against outstanding accounts receivable	52,500,000	46,300,000	41,900,000
Value of uncompensated care services	7,100,000	8,800,000	9,300,000
Estimated cost of providing charity services	$ 1,600,000	1,900,000	2,000,000
Percentage of reserved category of self pay	100.00%
Provisional income tax benefit related to remeasurement of deferred tax balances	$ 49,200,000
Allowance for doubtful accounts	7,200,000	6,000,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Unrealized losses recorded	300,000
Light Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairments of assets	400,000	400,000	0
Oil and Gas [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash proceeds	1,300,000	15,000,000	3,700,000
Gain (loss) on disposal of assets	$ 300,000	$ 3,300,000	$ 0
Oil and Gas [Member] | Light Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold | Aircraft		12	8
Number of Aircraft impaired | Aircraft	2
Carrying value of aircraft	$ 1,800,000
Oil and Gas [Member] | Light Aircraft [Member] | Fair Value, Inputs, Level 3 [Member]
Summary Of Significant Accounting Policies [Line Items]
Market value of aircraft	$ 1,400,000
Oil and Gas [Member] | Medium Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold | Aircraft	6	11	6
Oil and Gas [Member] | Fixed Wing Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold | Aircraft	1
Air Medical and Technical Services [Member]
Summary Of Significant Accounting Policies [Line Items]
Threshold customer percentage for operating revenue not exceeded during the year (percent)	2.00%	2.00%	2.00%
Air Medical [Member]
Summary Of Significant Accounting Policies [Line Items]
Allowance for contractual discounts against outstanding accounts receivable	$ 117,800,000	$ 111,900,000	$ 103,600,000
Allowance for uncompensated care against outstanding accounts receivable	$ 52,500,000	$ 46,300,000	41,900,000
Aircraft [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Salvage value of aircraft	54.00%
Aircraft [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Salvage value of aircraft	25.00%
Flight Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	15 years
Flight Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	5 years
Other Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	10 years
Other Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Leasehold Improvements [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	10 years
Leasehold Improvements [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life	6 years
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage owed by an overseas customer (percent)	10.70%
Aircraft [Member] | Oil and Gas [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment – net			3,700,000
Replacement Parts [Member] | Oil and Gas [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain (loss) on disposal of assets			$ (300,000)
Two Largest Customers [Member] | Oil and Gas [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of consolidated operating revenues	23.00%	24.00%	26.00%
Percentage of trade receivables	16.00%	16.00%
One Customer [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of trade receivables	10.00%	13.00%
One Customer [Member] | Air Medical [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of consolidated operating revenues		5.00%	9.00%

Summary of Significant Accoun43

Summary of Significant Accounting Policies - Provisions for Contractual Discounts and Uncompensated Care Applied to Air Medical Trade Receivables Expressed as Percentage of Total Segment Accounts Receivable (Detail) - Air Medical [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items]
Allowance for contractual discounts	66.00%	67.00%	65.00%
Trade Accounts Receivable [Member]
Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items]
Allowance for contractual discounts	53.00%	56.00%
Allowance for uncompensated care	24.00%	23.00%

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Goodwill Activity (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Goodwill [Roll Forward]
Goodwill, beginning	$ 0
Acquisition Activities	61,299
Goodwill, ending	61,299
Oil and Gas [Member]
Goodwill [Roll Forward]
Goodwill, beginning	0
Acquisition Activities	61,299
Goodwill, ending	61,299
Air Medical [Member]
Goodwill [Roll Forward]
Goodwill, beginning	0
Acquisition Activities	0
Goodwill, ending	0
Technical Services [Member]
Goodwill [Roll Forward]
Goodwill, beginning	0
Acquisition Activities	0
Goodwill, ending	$ 0

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Intangible Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Finite-Lived Intangible Assets [Line Items]
Gross amount	$ 16,723
Accumulated amortization	0
Net balance	16,723
Future Amortization Expense:
2,018	1,600
2,019	1,600
2,020	1,600
2,021	1,600
2,022	$ 1,600
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	15 years
Gross amount	$ 11,622
Accumulated amortization	0
Net balance	$ 11,622
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	5 years
Gross amount	$ 900
Accumulated amortization	0
Net balance	$ 900
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	7 years
Gross amount	$ 4,201
Accumulated amortization	0
Net balance	$ 4,201

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Schedule of Provisions for Contractual Discounts and Estimated Uncompensated Care Applied to Air Medical Revenues Expressed as Percentage of Total Independent Provider Model Billings (Detail) - Air Medical [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provisions For Contractual Discounts And Estimated Uncompensated Care [Line Items]
Provision for contractual discounts	66.00%	67.00%	65.00%
Provision for uncompensated care	7.00%	6.00%	8.00%

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Schedule of Net Revenue Attributable to Medicaid, Medicare, Private Insurance and Self Pay as Percentage of Net Air Medical Independent Provider Model Revenues (Detail) - Air Medical [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	72.00%	72.00%	74.00%
Medicare [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	18.00%	18.00%	17.00%
Medicaid [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	9.00%	9.00%	8.00%
Self Pay [Member]
Segment Reporting Information [Line Items]
Percentage of net Air Medical revenues	1.00%	1.00%	1.00%

Summary of Significant Accoun48

Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax expense	$ (58,973)	$ (469)	$ 16,332
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred tax liabilities	1,000
Income tax expense	900
Retained Earnings [Member] | Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	$ 1,000

Acquisition of Business (Detail

Acquisition of Business (Details) $ in Thousands, CAD in Millions	Dec. 29, 2017CAD	Dec. 29, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Aggregate principal amount of term loans provided			$ 824	$ 0	$ 0
Cumulative merger-related transaction costs			2,300
Purchaser [Member]
Business Acquisition [Line Items]
Aggregate principal amount of term loans provided	CAD 167.5	$ 131,600
Loans receivable expected to be repaid prior to December 31, 2019			$ 800

Acquisition of Business - Asset

Acquisition of Business - Assets acquired and Liabilities Assumed (Details) - USD ($)	Dec. 29, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Cash	$ 4,142
Accounts receivable	27,819
Inventories	3,096
Fixed assets	43,689
Intangible assets:
Other assets	5,310
Accounts payable and accrued liabilities	(25,272)
Deferred taxes	(5,270)
Other liabilities	(750)
Total identifiable net assets	69,487
Goodwill	61,299	$ 61,299,000	$ 0
Total consideration transferred	130,786
Noncompete Agreements [Member]
Intangible assets:
Intangible assets	$ 900
Weighted average useful life of intangible assets	5 years
Customer Relationships [Member]
Intangible assets:
Intangible assets	$ 11,622
Weighted average useful life of intangible assets	15 years
Trade Names [Member]
Intangible assets:
Intangible assets	$ 4,201
Weighted average useful life of intangible assets	7 years

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of short term investments	$ 862,942	$ 316,543	$ 505,966
Restricted cash and investments	$ 12,396	$ 13,038

Investments - Components of Inv

Investments - Components of Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 79,667	$ 305,915
Unrealized Gains	0	2
Unrealized Losses	(364)	(693)
Fair Value	79,303	305,224
Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	76,982	303,521
Unrealized Gains	0	2
Unrealized Losses	(364)	(693)
Fair Value	76,618	302,830
Investments [Member] | Money Market Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	5,601	18,118
Fair Value	5,601	18,118
Investments [Member] | Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	0	27,906
Unrealized Losses	0	(39)
Fair Value	0	27,867
Investments [Member] | US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	7,501	13,295
Unrealized Losses	(34)	(32)
Fair Value	7,467	13,263
Investments [Member] | Corporate Bonds and Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	63,880	244,202
Unrealized Gains	0	2
Unrealized Losses	(330)	(622)
Fair Value	63,550	243,582
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	2,685	2,394
Fair Value	$ 2,685	$ 2,394

Investments - Cost and Fair Val

Investments - Cost and Fair Value of Debt Investments Based on Maturities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, Amortized Costs	$ 31,348	$ 184,587
Due within two years, Amortized Costs	40,032	100,816
Total, Amortized Costs	71,380	285,403
Due in one year or less, Fair Value	31,254	184,334
Due within two years, Fair Value	39,763	100,378
Total, Fair Value	$ 71,017	$ 284,712

Investments - Average Coupon Ra

Investments - Average Coupon Rate Percentage and the Average Days to Maturity of Debt (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Average Coupon Rate	0.00%	1.001%
Average Days To Maturity	0 days	184 days
US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Average Coupon Rate	1.37%	0.97%
Average Days To Maturity	370 days	400 days
Corporate Bonds and Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Average Coupon Rate	1.766%	1.745%
Average Days To Maturity	392 days	318 days

Investments - Investments in Co

Investments - Investments in Continuous Unrealized Loss Position for Less Than Twelve Months (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 49,541	$ 251,966
Unrealized Losses	(299)	(673)
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	0	27,867
Unrealized Losses	0	(39)
US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	5,472	13,263
Unrealized Losses	(28)	(32)
Corporate Bonds and Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	44,069	210,836
Unrealized Losses	$ (271)	$ (602)

Investments - Investments in 56

Investments - Investments in Continuous Unrealized Loss Position for More Than Twelve Months (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 21,476	$ 24,196
Unrealized Losses	(65)	(20)
US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,994	0
Unrealized Losses	(6)	0
Corporate Bonds and Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	19,482	24,196
Unrealized Losses	$ (59)	$ (20)

Fair Value - Summary of Valuati

Fair Value - Summary of Valuation of Investments and Financial Instruments Pricing Levels (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 79,303	$ 305,224
Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	76,618	302,830
Investments [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	5,601	18,118
Investments [Member] | Corporate Bonds and Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	63,550	243,582
Investments [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0	27,867
Investments [Member] | US Government Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	7,467	13,263
Deferred Compensation Plan Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	2,685	2,394
(Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	8,286	20,512
(Level 1) [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	5,601	18,118
(Level 1) [Member] | Investments [Member] | Money Market Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	5,601	18,118
(Level 1) [Member] | Deferred Compensation Plan Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	2,685	2,394
(Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	71,017	284,712
(Level 2) [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	71,017	284,712
(Level 2) [Member] | Investments [Member] | Corporate Bonds and Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	63,550	243,582
(Level 2) [Member] | Investments [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0	27,867
(Level 2) [Member] | Investments [Member] | US Government Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 7,467	$ 13,263

Fair Value - Summary of Combine

Fair Value - Summary of Combined Fair Value of Assets that Incurred Impairments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Amount of impairment incurred	$ 368	$ 407	$ 0
Combined fair value of assets incurring impairment, after impairment charges	$ 1,380	$ 1,380	$ 0

Fair Value - Additional Informa

Fair Value - Additional Information (Details) - Senior Notes [Member] - 5.25% Senior Notes due March 15, 2019 [Member] - USD ($) $ in Millions	Dec. 31, 2017	Mar. 17, 2014
Debt Instrument [Line Items]
Interest rate on Senior Notes	5.25%	5.25%
Senior notes, fair value	$ 499.2

Property and Equipment - Summar

Property and Equipment - Summary of Company's Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,377,260	$ 1,287,546
Less accumulated depreciation and amortization	(430,495)	(383,569)
Property and equipment, net	946,765	903,977
Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,225,205	1,144,315
Facility & Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	64,316	61,187
Operating Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	29,913	25,966
Data Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	34,747	33,881
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,202	8,567
Medical Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,354	7,963
Other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,523	$ 5,667

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation expense related to property and equipment	$ 50.6	$ 49.2	$ 46.7

Other Assets - Schedule of Comp

Other Assets - Schedule of Company's Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deposits on future purchases of aircraft	$ 501	$ 4,818
Investment in Variable Interest Entity	330	1,351
Investments (Officers' Deferred Compensation Plan)	2,685	2,394
Other	5,225	1,196
Total	$ 8,741	$ 9,759

Accrued and Other Current Lia63

Accrued and Other Current Liabilities - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Salaries & wages	$ 6,240	$ 5,949
Incentive compensation	8,991	1,576
Income taxes	930	587
Interest	8,108	8,057
Vacation payable	7,619	5,700
Group medical	1,344	1,892
Transportations tax	971	427
Operating lease	710	769
Workers compensation	959	865
Other	5,978	2,524
Total accrued liabilities	$ 41,850	$ 28,346

Long Term Debt - Components of

Long Term Debt - Components of Long-term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Principal	$ 617,500	$ 634,000
Unamortized debt issuance debt costs	1,506	2,753
5.25% Senior Notes due March 15, 2019 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Principal	500,000	500,000
Unamortized debt issuance debt costs	1,506	2,753
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal	$ 117,500	$ 134,000

Long Term Debt - Summary of Ann

Long Term Debt - Summary of Annual Maturities of Long-term Debt (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 0
2,019	617,500
2,020	0
2,021	0
2,022	0
Thereafter	0
Total	$ 617,500

Long Term Debt - Additional Inf

Long Term Debt - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Mar. 17, 2014
Debt Instrument [Line Items]
Carrying value of Long-term Debt	$ 615,994,000	$ 631,247,000
Short-term investment limit	64,237,000	289,806,000
Letters of credit outstanding under the facility	$ 12,400,000	13,000,000
Middle East [Member]
Debt Instrument [Line Items]
Revolving credit facility, maturity date	Oct. 29, 2018
Letter of credit securing workers compensation policy	$ 9,200,000
5.25% Senior Notes due March 15, 2019 [Member]
Debt Instrument [Line Items]
Carrying value of Long-term Debt	500,000,000	500,000,000
Fair market value of Senior Notes	$ 499,200,000	474,400,000
5.25% Senior Notes due March 15, 2019 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	5.25%				5.25%
Percentage of principal amount redeemed	101.00%
Debt instrument restrictive covenants	The Notes contain restrictive covenants, including limitations on incurring indebtedness, creating liens, selling assets, and entering into certain transactions with affiliates. The covenants limit our ability to pay cash dividends on common stock, repurchase or redeem common or preferred equity, prepay subordinated debt, and make certain investments.
Debt Instrument, Maturity Date	Mar. 15, 2019
Interest Expense Fund [Member]
Debt Instrument [Line Items]
Periodic payment of debt interest	$ 30,500,000	$ 29,200,000	$ 27,700,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Increased Borrowing capacity	$ 130,000,000			$ 150,000,000
Revolving Credit facility, Covenants, consolidated working capital ratio	200.00%
Revolving Credit facility, Covenants, consolidated net worth ratio	150.00%
Revolving Credit facility, Covenants, fixed coverage ratio	100.00%			110.00%
Revolving Credit facility, Covenants, consolidated net worth	$ 500,000,000			$ 450,000,000
Debt Covenant, Debt Limit	5,000,000
Letters of credit outstanding under the facility	7,600,000
Letter of credit securing workers compensation policy	$ 3,200,000
Revolving Credit Facility [Member] | LIBOR [Member]
Debt Instrument [Line Items]
LIBOR plus interest rate on borrowed funds	2.75%
Minimum [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Short-term investment limit	$ 150,000,000

Income Taxes - Income before Ta

Income Taxes - Income before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
United States									$ (50,871)	$ (25,604)	$ 45,038
Foreign									(570)	(1,546)	(1,782)
(Loss) earnings before income taxes	$ (20,319)	$ (4,899)	$ (3,150)	$ (23,073)	$ (12,012)	$ (7,766)	$ 117	$ (7,488)	$ (51,441)	$ (27,149)	$ 43,256

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S. Federal:
Current	$ 0	$ 0	$ 0
Deferred	(57,637)	(5,488)	13,629
U. S. Federal Income Tax Expense (Benefit)	(57,637)	(5,488)	13,629
U.S. State:
Current	199	427	284
Deferred	(717)	3,218	(740)
State and Local Income Tax Expense (Benefit)	(518)	3,645	(456)
Foreign Income Tax Expense (Benefit), Continuing Operations [Abstract]
Foreign	108	1,374	3,159
Deferred	(926)	0	0
Foreign Income Tax Expense (Benefit)	(818)	1,374	3,159
Total	$ (58,973)	$ (469)	$ 16,332

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)States	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Income Taxes Disclosure [Line Items]
Federal Statutory rate (percent)	35.00%	35.00%	35.00%
Provisional income tax benefit related to remeasurement of deferred tax balances	$ 49,200,000
Impact on state apportionment percentage changes on income tax expense (benefit)		$ (4,800,000)	$ 1,000,000
Operating loss carryforwards	$ 297,200,000
Operating loss carryforwards, expiration date start	2,026
Operating loss carryforwards, expiration date end	2,037
Net operating loss carryforwards, majority expiration date start	2,024
Net operating loss carryforwards, majority expiration date end	2,037
Number of states where net operating losses will likely be forfeited | States	6
Net deferred tax liabilities	$ 82,696,000	140,915,000
Foreign tax credits	19,453,000	21,492,000
Australian net operating loss carryforward	1,300,000
Valuation allowance - tax credit carryforwards	16,600,000
Valuation allowance - tax credit carryforwards recorded in 2014	7,500,000
Income taxes paid	1,231,000	2,637,000	$ 5,521,000
Unrecognized tax benefits	0
State and Local Jurisdiction [Member]
Income Taxes Disclosure [Line Items]
Operating loss carryforwards	$ 239,500,000
Operating loss carryforwards, expiration date end	2,037
Valuation allowance - state NOL carryforwards	$ 5,998,000	$ 5,318,000
State and Local Jurisdiction [Member] | Valuation Allowance, Operating Loss Carryforwards [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance - state NOL carryforwards	900,000
Australian Operation [Member]
Income Taxes Disclosure [Line Items]
Net deferred tax assets	3,300,000
Deferred tax assets, net operating loss	14,500,000
New Zealand Operation [Member]
Income Taxes Disclosure [Line Items]
Net deferred tax liabilities	$ 200,000

Income Taxes - Schedule of In70

Income Taxes - Schedule of Income Tax Expense as Percentage of Pre-Tax Earnings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes at statutory rate (percent)	35.00%	35.00%	35.00%
Valuation allowance on foreign tax credits (percent)	(12.00%)	(33.00%)	0.00%
Valuation allowance on state net operating loss carryforwards (percent)	(2.00%)	(19.00%)	0.00%
Valuation allowance reversal- investment in foreign entity (percent)		0.00%	(1.00%)
Valuation Allowance – Other (percent)	(3.00%)	0.00%	0.00%
Change in tax rate on deferred items (percent)	0.00%	18.00%	3.00%
Tax reform – Impact of change in tax rate (percent)	96.00%	0.00%	0.00%
State income taxes, net of federal benefit (percent)	3.00%	5.00%	0.00%
Other items - net (percent)	(2.00%)	(4.00%)	1.00%
Total (percent)	115.00%	2.00%	38.00%
Increase (decrease) in taxes resulting from:
Income taxes at statutory rate	$ (18,004)	$ (9,502)	$ 15,140
Valuation allowance on foreign tax credits	6,145	8,991	0
Valuation allowance on state net operating loss carryforwards	868	5,028	0
Valuation allowance reversal- investment in foreign entity	0	0	(456)
Valuation Allowance - Other	1,353	0	0
Change in tax rate on deferred items	0	(4,772)	1,078
Tax reform – Impact of change in tax rate	(49,219)	0	0
State income taxes, net of federal benefit	(1,386)	(1,384)	146
Other items - net	1,270	1,170	424
Total	$ (58,973)	$ (469)	$ 16,332

Income Taxes - Schedule of Tax

Income Taxes - Schedule of Tax Effects of Temporary Differences that Give Rise to Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Deferred compensation	$ 626	$ 937
Foreign tax credits	19,453	21,492
Vacation and bonus accrual	3,936	1,674
Inventory valuation	4,954	7,655
Rental accrual	747	1,416
Hurricane relief credit	1,255	1,255
Stock-based compensation	988	2,202
Other	2,235	3,115
Net operating losses	82,044	89,256
Total deferred tax assets	116,238	129,002
Valuation allowance - tax credit carryforwards	(16,537)	(11,039)
Total deferred tax assets, net	93,605	112,645
Deferred tax liabilities:
Tax depreciation in excess of book depreciation	(171,116)	(253,560)
Other	(5,185)	0
Total deferred tax liabilities	(176,301)	(253,560)
Net deferred tax liabilities	(82,696)	(140,915)
Deferred tax assets – short-term	0	10,798
Deferred tax assets – long-term	3,309	0
Deferred tax liability - long-term	(86,005)	(151,713)
Net deferred tax liabilities	(82,696)	(140,915)
State and Local Jurisdiction [Member]
Deferred tax assets:
Valuation allowance - state NOL carryforwards	(5,998)	(5,318)
Foreign Tax Authority [Member]
Deferred tax assets:
Valuation allowance - state NOL carryforwards	$ (98)	$ 0

Earnings Per Share - Components

Earnings Per Share - Components of Basic and Diluted Earnings Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average outstanding shares of common stock, basic	15,762	15,663	15,566
Dilutive effect of unvested restricted stock units	0	0	76
Weighted average outstanding shares of common stock, diluted	15,762	15,663	15,642

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Anti-dilutive securities	0	24,468	0

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)CompensationPlan	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Aggregate deferred under Compensation Plan	$ 2.7	$ 2.4
Number of incentive compensation plans | CompensationPlan	1
Earnings before tax upon achieving a specified earnings threshold	3.00%
Accrued Incentive Compensation expense	$ 9	1.6	$ 3
Percentage of employee compensation contribution	6.00%
Percentage of vesting contribution	25.00%
Vesting period of employees	5 years
Matching contribution of employees	$ 9.5	10.1	11.8
Safety Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Compensation expense related to incentive plans	$ 0.6	$ 0.9	$ 0.9

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Based Compensation [Line Items]
Compensation expense related to incentive plans	$ 4,400,000	$ (100,000)	$ 5,800,000
Non-Voting Time-Vested Restricted Stock Units [Member]
Stock Based Compensation [Line Items]
Weighted average grant date fair value	$ 11.42	$ 20.07
Aggregate value of vested shares	$ 1,500,000	$ 200,000
Recognized / Unrecognized compensation cost	$ 4,100,000
Weighted average period	2 years 3 months 4 days
Aggregate value of forfeited shares		$ 100,000
Non-Voting Time-Vested Restricted Stock Units [Member] | Maximum [Member]
Stock Based Compensation [Line Items]
Aggregate value of forfeited shares	$ 400,000
Non-Voting Performance Based Restricted Stock Units [Member]
Stock Based Compensation [Line Items]
Weighted average grant date fair value	$ 15.11
Aggregate value of vested shares	$ 0
Recognized / Unrecognized compensation cost	3,300,000
Aggregate value of forfeited shares	5,100,000
Reduction in compensation expense	$ (2,800,000)
2012 Long - Term Incentive Plan [Member] | Amended and Restated 2015 Long Term Incentive Plan [Member]
Stock Based Compensation [Line Items]
Shares available for issuance	1,806,315
Forfeiture restrictions percentage	100.00%
Vesting period of employees	3 years
2012 Long - Term Incentive Plan [Member] | Amended and Restated 2015 Long Term Incentive Plan [Member] | Non-Voting Common Stock [Member]
Stock Based Compensation [Line Items]
Common stock authorized to issue	3,500,000

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Activity for Non-voting Time-vested Restricted Stock (Detail) - Non-Voting Time-Vested Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share unit, Beginning Balance	202,560
Share unit, Granted	480,065
Share unit, Forfeited	(10,211)
Share unit, Vested and released to participants	(137,703)
Share unit, Ending Balance	534,711	202,560
Weighted Average Grant Fair Value, Beginning Balance	$ 37.91
Weighted Average Grants Date Fair Value, Granted	11.42	$ 20.07
Weighted Average Grants Date Fair Value, Forfeited	10.01
Weighted Average Grants Date Fair Value, Vested and released to participants	41.76
Weighted Average Grant Fair Value, Ending Balance	$ 12.80	$ 37.91
Remaining Average Contractual Life, Ending	2 years 3 months 4 days	1 year 3 months
Aggregate Value	$ 6,844	$ 7,679

Stock-based Compensation - Su77

Stock-based Compensation - Summary of Activity for Non-voting Time-vested Restricted Stock Granted to Directors (Detail) - Non-Voting Time-Vested Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share unit, Beginning Balance	202,560
Share unit, Granted	480,065
Share unit, Forfeited	(10,211)
Share unit, Vested and released to participants	(137,703)
Share unit, Ending Balance	534,711	202,560
Weighted Average Grant Fair Value, Beginning Balance	$ 37.91
Weighted Average Grants Date Fair Value, Granted	11.42	$ 20.07
Weighted Average Grants Date Fair Value, Forfeited	10.01
Weighted Average Grants Date Fair Value, Vested and released to participants	41.76
Weighted Average Grant Fair Value, Ending Balance	$ 12.80	$ 37.91
Remaining Average Contractual Life, Ending	2 years 3 months 4 days	1 year 3 months
Aggregate Value	$ 6,844	$ 7,679
Director [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share unit, Beginning Balance	11,559
Share unit, Granted	10,323
Share unit, Forfeited	0
Share unit, Vested and released to participants	(2,202)
Share unit, Ending Balance	19,680	11,559
Weighted Average Grant Fair Value, Beginning Balance	$ 23.01
Weighted Average Grants Date Fair Value, Granted	11.91
Weighted Average Grants Date Fair Value, Forfeited	0
Weighted Average Grants Date Fair Value, Vested and released to participants	44.04
Weighted Average Grant Fair Value, Ending Balance	$ 14.94	$ 23.01
Remaining Average Contractual Life, Ending	2 years 8 months 16 days	2 years 1 month 17 days
Aggregate Value	$ 292	$ 266

Stock-based Compensation - Su78

Stock-based Compensation - Summary of Activity for Non-voting Performance Units (Detail) - Non-Voting Performance Based Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share unit, Beginning Balance	569,418
Share unit, Granted	371,045
Share unit, Forfeited	(122,313)
Share unit, Vested and released to participants	0
Share unit, Ending Balance	818,150	569,418
Weighted Average Grant Fair Value, Beginning Balance	$ 25.83
Weighted Average Grants Date Fair Value, Granted	15.11
Weighted Average Grants Date Fair Value, Forfeited	41.64
Weighted Average Grants Date Fair Value, Vested and released to participants	0
Weighted Average Grant Fair Value, Ending Balance	$ 18.60	$ 25.83
Remaining Average Contractual Life, Ending	1 year 2 months 12 days	1 year 2 months 9 days
Aggregate Value	$ 15,218	$ 14,708

Commitments and Contingencies -

Commitments and Contingencies - Summary of Rental Expense Incurred Under Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Aircraft	$ 39,815	$ 44,130	$ 45,360
Other	9,504	9,451	8,358
Total	$ 49,319	$ 53,581	$ 53,718

Commitments and Contingencies80

Commitments and Contingencies - Summary of Remaining Aggregate Lease Commitments Under Operating Leases Having Initial Non-Cancelable Terms in Excess of One Year (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leased Assets [Line Items]
2,018	$ 40,880
2,019	34,915
2,020	30,714
2,021	29,740
2,022	27,911
Thereafter	38,909
Total	203,069
Other [Member]
Operating Leased Assets [Line Items]
2,018	5,157
2,019	3,670
2,020	3,308
2,021	2,468
2,022	1,153
Thereafter	9,832
Total	25,588
Aircraft [Member]
Operating Leased Assets [Line Items]
2,018	35,723
2,019	31,245
2,020	27,406
2,021	27,272
2,022	26,758
Thereafter	29,077
Total	$ 177,481

Commitments and Contingencies81

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Land_Parcel	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Long-term Purchase Commitment [Line Items]
Aircraft and real estate rental expense	$ 49,319	$ 53,581	$ 53,718
Aggregate amount of guarantees and bonds	1,000
Total aircraft deposits	501	$ 4,818
Aggregate estimated probable liability environmental matters	$ 150
Number of parcels of land exists | Land_Parcel	2
2018 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	$ 127,000
2019 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	129,000
2020 [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase price for aircraft	$ 22,700

Business Segments and Geograp82

Business Segments and Geographic Areas - Schedule of Accounts Receivable and Revenue by Major Customers by Reporting Segments (Detail) - Segment	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Number of reportable segments	3
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	10.70%
Customer Concentration Risk [Member] | Oil and Gas [Member] | Operating Revenues [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	14.00%	14.00%	15.00%
Customer Concentration Risk [Member] | Oil and Gas [Member] | Operating Revenues [Member] | Customer B [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	9.00%	10.00%	11.00%
Customer Concentration Risk [Member] | Air Medical and Technical Services [Member] | Operating Revenues [Member] | Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	0.00%	5.00%	9.00%
Concentration of Credit Risk [Member] | Oil and Gas [Member] | Accounts Receivable [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	11.00%	8.00%
Concentration of Credit Risk [Member] | Oil and Gas [Member] | Accounts Receivable [Member] | Customer B [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	5.00%	8.00%
Concentration of Credit Risk [Member] | Air Medical and Technical Services [Member] | Accounts Receivable [Member] | Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	10.00%	13.00%

Business Segments and Geograp83

Business Segments and Geographic Areas - Schedule of Financial Information Concerning Reportable Operating Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total operating revenues	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
Total segment direct expenses									546,699	592,550	687,050
Total segment selling, general and administrative expenses									53,817	44,418	46,422
Total net segment profit									(22,022)	224	70,111
Interest expense									(32,183)	(30,644)	(29,066)
(Loss) earnings before income taxes	$ (20,319)	$ (4,899)	$ (3,150)	$ (23,073)	$ (12,012)	$ (7,766)	$ 117	$ (7,488)	(51,441)	(27,149)	43,256
Reportable Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues									579,545	634,098	804,228
Total segment direct expenses									547,084	592,399	687,356
Total segment selling, general and administrative expenses									19,746	18,808	17,771
Total segment expenses									566,830	611,207	705,127
Total net segment profit									12,715	22,891	99,101
Reportable Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting Information [Line Items]
Total operating revenues									298,398	324,129	459,611
Total segment direct expenses									321,272	344,640	411,757
Total segment selling, general and administrative expenses									5,899	6,739	6,511
Total net segment profit									(28,773)	(27,250)	41,343
Reportable Operating Segments [Member] | Air Medical [Member]
Segment Reporting Information [Line Items]
Total operating revenues									257,273	281,868	312,775
Total segment direct expenses									208,987	227,877	246,487
Total segment selling, general and administrative expenses									12,442	10,968	10,455
Total net segment profit									35,844	43,023	55,833
Reportable Operating Segments [Member] | Technical Services [Member]
Segment Reporting Information [Line Items]
Total operating revenues									23,874	28,101	31,842
Total segment direct expenses									16,825	19,882	29,112
Total segment selling, general and administrative expenses									1,405	1,101	805
Total net segment profit									5,644	7,118	1,925
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other, net									2,098	6,214	1,872
Interest expense									(32,183)	(30,644)	(29,066)
Corporate [Member]
Segment Reporting Information [Line Items]
Unallocated selling, general and administrative costs									$ (34,071)	$ (25,610)	$ (28,651)

Business Segments and Geograp84

Business Segments and Geographic Areas - Summary of Gains on Disposition of Property and Equipment and Other Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	$ 58,478	$ 82,871	$ 56,575
Depreciation and amortization	68,027	65,743	71,618
Total assets	1,401,846	1,448,440
Reportable Operating Segments [Member] | Oil and Gas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	52,525	59,278	32,501
Depreciation and amortization	39,655	40,170	42,709
Total assets	722,734	674,788
Reportable Operating Segments [Member] | Air Medical [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	5,696	22,429	22,685
Depreciation and amortization	20,413	19,716	18,177
Total assets	372,646	368,474
Reportable Operating Segments [Member] | Technical Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Depreciation and amortization	581	564	518
Total assets	5,979	9,568
Corporate [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Expenditures for long-lived assets	257	1,164	1,389
Depreciation and amortization	7,378	5,293	$ 10,214
Total assets	$ 300,487	$ 395,610

Business Segments and Geograp85

Business Segments and Geographic Areas - Summary of Company's Revenues from External Customers and Long-Lived Assets, by Geographical Areas (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total operating revenues	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
Total Long-Lived Assets	946,765				903,977				946,765	903,977
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total operating revenues									530,115	579,300	722,339
Total Long-Lived Assets	601,530				751,290				601,530	751,290
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total operating revenues									49,430	54,798	$ 81,889
Total Long-Lived Assets	$ 345,235				$ 152,687				$ 345,235	$ 152,687

Quarterly Financial Data - Summ

Quarterly Financial Data - Summary of Condensed Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Operating revenues, net	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
(Loss) gain on disposition of assets, net	287	4	7	0	(504)	(85)	4,298	(359)	(298)	3,350	(339)
(Loss) earnings before income taxes	(20,319)	(4,899)	(3,150)	(23,073)	(12,012)	(7,766)	117	(7,488)	(51,441)	(27,149)	43,256
Net earnings (loss)	$ 29,330	$ (3,277)	$ (3,273)	$ (15,248)	$ (17,058)	$ (4,967)	$ 4,277	$ (8,932)	$ 7,532	$ (26,680)	$ 26,924
Net (loss) earnings per share
Basic (USD per share)	$ 1.87	$ (0.21)	$ (0.21)	$ (0.97)	$ (1.08)	$ (0.32)	$ 0.27	$ (0.57)	$ 0.48	$ (1.70)	$ 1.73
Diluted (USD per share)	$ 1.87	$ (0.21)	$ (0.21)	$ (0.97)	$ (1.08)	$ (0.32)	$ 0.27	$ (0.57)	$ 0.48	$ (1.70)	$ 1.72

Variable Interest Entity - Addi

Variable Interest Entity - Additional Information (Detail) - USD ($) $ in Millions	Dec. 29, 2017	Dec. 31, 2016	Dec. 31, 2017
PHI Century Limited [Member]
Variable Interest Entity [Line Items]
Investment in the common stock			49.00%
PHIC's date of incorporation			May 26, 2011
Earnings (loss) in equity of unconsolidated affiliate			$ 1
Trade receivables			4
Other assets		$ 0.2	0.3
PHI-HNZ Australia Ltd [Member]
Variable Interest Entity [Line Items]
Investment in the common stock	100.00%	50.00%
Earnings (loss) in equity of unconsolidated affiliate			$ 0.6
HNZ Group, Inc. [Member] | PHI-HNZ Australia Ltd [Member]
Variable Interest Entity [Line Items]
Investment in the common stock		50.00%

Condensed Consolidating Finan88

Condensed Consolidating Financial Information - Guarantor Subsidiaries - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Sep. 30, 2017	Mar. 17, 2014
Supplemental Guarantor Financial Information [Line Items]
Ownership of subsidiaries (percent)		100.00%
5.25% Senior Notes due March 15, 2019 [Member] | Senior Notes [Member]
Supplemental Guarantor Financial Information [Line Items]
Debt issued			$ 500,000,000
Interest rate on Senior Notes	5.25%		5.25%

Condensed Consolidating Finan89

Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Balance Sheets (Detail) - USD ($)	Dec. 31, 2017	Dec. 29, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash	$ 8,770,000		$ 2,596,000	$ 2,407,000	$ 6,270,000
Short-term investments	64,237,000		289,806,000
Accounts receivable - net	185,979,000		138,265,000
Inventories of spare parts – net	80,881,000		70,402,000
Prepaid expenses	11,475,000		9,259,000
Deferred income taxes	0		10,798,000
Income taxes receivable	1,271,000		540,000
Total current assets	352,613,000		521,666,000
Property and equipment – net	946,765,000		903,977,000
Restricted cash and investments	12,396,000		13,038,000
Other assets	8,741,000		9,759,000
Deferred income taxes	3,309,000		0
Goodwill	61,299,000	$ 61,299	0
Intangibles	16,723,000		0
Total assets	1,401,846,000		1,448,440,000
Current Liabilities:
Accounts payable	37,186,000		28,704,000
Accrued and other current liabilities	41,850,000		28,346,000
Total current liabilities	79,036,000		57,050,000
Long-term debt	615,994,000		631,247,000
Deferred income taxes and other long-term liabilities	94,162,000		160,365,000
Shareholders’ Equity:
Common stock and paid-in capital	309,933,000		305,815,000
Accumulated other comprehensive loss	(280,000)		(478,000)
Retained earnings	303,001,000		294,441,000
Total shareholders’ equity	612,654,000		599,778,000	626,998,000	597,068,000
Total liabilities and shareholders’ equity	1,401,846,000		1,448,440,000
Parent Company Only (issuer) [Member]
Current Assets:
Cash	47,000		36,000	46,000	51,000
Short-term investments	64,237,000		289,806,000
Accounts receivable - net	90,077,000		71,458,000
Inventories of spare parts – net	68,737,000		61,834,000
Prepaid expenses	8,348,000		6,990,000
Deferred income taxes			10,798,000
Income taxes receivable	345,000		558,000
Total current assets	231,791,000		441,480,000
Investment in subsidiaries and others	397,301,000		353,160,000
Property and equipment – net	617,488,000		589,104,000
Restricted cash and investments	12,382,000		13,023,000
Other assets	139,754,000		8,660,000
Total assets	1,398,716,000		1,405,427,000
Current Liabilities:
Accounts payable	28,130,000		22,744,000
Accrued and other current liabilities	23,147,000		18,725,000
Intercompany payable	113,387,000		57,904,000
Total current liabilities	164,664,000		99,373,000
Long-term debt	615,994,000		631,247,000
Deferred income taxes and other long-term liabilities	5,404,000		75,029,000
Shareholders’ Equity:
Common stock and paid-in capital	309,933,000		305,815,000
Accumulated other comprehensive loss	(280,000)		(478,000)
Retained earnings	303,001,000		294,441,000
Total shareholders’ equity	612,654,000		599,778,000
Total liabilities and shareholders’ equity	1,398,716,000		1,405,427,000
Guarantor Subsidiaries [Member]
Current Assets:
Cash	1,072,000		2,100,000	1,672,000	5,966,000
Accounts receivable - net	74,886,000		62,868,000
Intercompany receivable	126,366,000		91,040,000
Inventories of spare parts – net	9,049,000		8,568,000
Prepaid expenses	1,898,000		2,184,000
Income taxes receivable	9,000		(18,000)
Total current assets	213,280,000		166,742,000
Property and equipment – net	284,984,000		294,197,000
Other assets	908,000		1,099,000
Total assets	499,172,000		462,038,000
Current Liabilities:
Accounts payable	4,636,000		5,822,000
Accrued and other current liabilities	10,577,000		9,418,000
Total current liabilities	15,213,000		15,240,000
Deferred income taxes and other long-term liabilities	84,300,000		85,336,000
Shareholders’ Equity:
Common stock and paid-in capital	77,951,000		77,951,000
Retained earnings	321,708,000		283,511,000
Total shareholders’ equity	399,659,000		361,462,000
Total liabilities and shareholders’ equity	499,172,000		462,038,000
Non-Guarantor Subsidiaries [Member]
Current Assets:
Cash	7,651,000		460,000	689,000	253,000
Accounts receivable - net	38,020,000		3,939,000
Intercompany receivable			(33,136,000)
Inventories of spare parts – net	3,095,000
Prepaid expenses	1,229,000		85,000
Income taxes receivable	917,000
Total current assets	50,912,000		(28,652,000)
Property and equipment – net	44,293,000		20,676,000
Restricted cash and investments	14,000		15,000
Other assets	(131,921,000)
Deferred income taxes	3,309,000
Goodwill	61,299,000
Intangibles	16,723,000
Total assets	44,629,000		(7,961,000)
Current Liabilities:
Accounts payable	21,425,000		138,000
Accrued and other current liabilities	8,126,000		203,000
Intercompany payable	12,978,000
Total current liabilities	42,529,000		341,000
Deferred income taxes and other long-term liabilities	4,458,000
Shareholders’ Equity:
Common stock and paid-in capital	1,375,000		1,240,000
Retained earnings	(3,733,000)		(9,542,000)
Total shareholders’ equity	(2,358,000)		(8,302,000)
Total liabilities and shareholders’ equity	44,629,000		(7,961,000)
Eliminations [Member]
Current Assets:
Cash	0		0	$ 0	$ 0
Accounts receivable - net	(17,004,000)
Intercompany receivable	(126,366,000)		(57,904,000)
Total current assets	(143,370,000)		(57,904,000)
Investment in subsidiaries and others	(397,301,000)		(353,160,000)
Total assets	(540,671,000)		(411,064,000)
Current Liabilities:
Accounts payable	(17,005,000)
Intercompany payable	(126,365,000)		(57,904,000)
Total current liabilities	(143,370,000)		(57,904,000)
Shareholders’ Equity:
Common stock and paid-in capital	(79,326,000)		(79,191,000)
Retained earnings	(317,975,000)		(273,969,000)
Total shareholders’ equity	(397,301,000)		(353,160,000)
Total liabilities and shareholders’ equity	$ (540,671,000)		$ (411,064,000)

Condensed Consolidating Finan90

Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Operating revenues, net	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
Expenses:
Direct expenses									546,699	592,550	687,050
Selling, general, and administrative expenses									53,817	44,418	46,422
Total operating expenses									600,516	636,968	733,472
Loss (gain) on disposition of assets, net	(287)	(4)	(7)	0	504	85	(4,298)	359	298	(3,350)	339
Impairment of assets									368	407	0
Equity in profit (loss) of unconsolidated affiliate									385	(151)	306
Operating (loss) income									(22,022)	224	70,111
Interest expense									32,183	30,644	29,066
Other income, net									(2,764)	(3,271)	(2,211)
Total expenses									29,419	27,373	26,855
(Loss) earnings before income taxes	(20,319)	(4,899)	(3,150)	(23,073)	(12,012)	(7,766)	117	(7,488)	(51,441)	(27,149)	43,256
Income tax (benefit) expense									(58,973)	(469)	16,332
Net earnings (loss)	$ 29,330	$ (3,277)	$ (3,273)	$ (15,248)	$ (17,058)	$ (4,967)	$ 4,277	$ (8,932)	7,532	(26,680)	26,924
Parent Company Only (issuer) [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net									310,449	339,829	476,969
Expenses:
Direct expenses									326,152	347,532	426,239
Selling, general, and administrative expenses									41,134	32,911	35,694
Total operating expenses									367,286	380,443	461,933
Loss (gain) on disposition of assets, net									300	(3,350)	339
Impairment of assets									368	407
Equity in profit (loss) of unconsolidated affiliate									1,021	(151)	306
Operating (loss) income									(58,526)	(37,520)	14,391
Equity in net earnings of consolidated subsidiaries									(38,553)	(22,182)	(31,225)
Interest expense									32,161	30,585	28,946
Other income, net									(2,757)	(3,284)	(2,222)
Total expenses									(9,149)	5,119	(4,501)
(Loss) earnings before income taxes									(49,377)	(42,639)	18,892
Income tax (benefit) expense									(56,909)	(15,959)	(8,032)
Net earnings (loss)									7,532	(26,680)	26,924
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net									262,229	293,329	327,259
Expenses:
Direct expenses									212,691	237,635	259,198
Selling, general, and administrative expenses									12,462	10,984	10,577
Total operating expenses									225,153	248,619	269,775
Loss (gain) on disposition of assets, net									(2)
Operating (loss) income									37,078	44,710	57,484
Interest expense									22	46	120
Other income, net									(2)	(5)	(7)
Total expenses									20	41	113
(Loss) earnings before income taxes									37,058	44,669	57,371
Income tax (benefit) expense									(1,138)	15,490	24,364
Net earnings (loss)									38,196	29,179	33,007
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net									23,871	940
Expenses:
Direct expenses									24,860	7,383	1,631
Selling, general, and administrative expenses									221	541	151
Total operating expenses									25,081	7,924	1,782
Equity in profit (loss) of unconsolidated affiliate									(636)
Operating (loss) income									(574)	(6,984)	(1,782)
Interest expense										13
Other income, net									(5)
Total expenses									(5)	13	0
(Loss) earnings before income taxes									(569)	(6,997)	(1,782)
Income tax (benefit) expense									(926)
Net earnings (loss)									357	(6,997)	(1,782)
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Operating revenues, net									(17,004)
Expenses:
Direct expenses									(17,004)		(18)
Selling, general, and administrative expenses										(18)
Total operating expenses									(17,004)	(18)	(18)
Operating (loss) income									0	18	18
Equity in net earnings of consolidated subsidiaries									38,553	22,182	31,225
Other income, net									0	18	18
Total expenses									38,553	22,200	31,243
(Loss) earnings before income taxes									(38,553)	(22,182)	(31,225)
Net earnings (loss)									$ (38,553)	$ (22,182)	$ (31,225)

Condensed Consolidating Finan91

Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidated Statements of Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net earnings (loss)	$ 29,330	$ (3,277)	$ (3,273)	$ (15,248)	$ (17,058)	$ (4,967)	$ 4,277	$ (8,932)	$ 7,532	$ (26,680)	$ 26,924
Unrealized gain (loss) on short-term investments									310	241	(641)
Other unrealized gain									0	0	24
Changes in pension plan assets and benefit obligations									(3)	(39)	7
Tax effect									(109)	(113)	254
Total comprehensive (loss) income									7,730	(26,591)	26,568
Parent Company Only (issuer) [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings (loss)									7,532	(26,680)	26,924
Unrealized gain (loss) on short-term investments									310	241	(641)
Other unrealized gain											24
Changes in pension plan assets and benefit obligations									(3)	(39)	7
Tax effect									(109)	(113)	254
Total comprehensive (loss) income									7,730	(26,591)	26,568
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings (loss)									38,196	29,179	33,007
Total comprehensive (loss) income									38,196	29,179	33,007
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings (loss)									357	(6,997)	(1,782)
Total comprehensive (loss) income									357	(6,997)	(1,782)
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net earnings (loss)									(38,553)	(22,182)	(31,225)
Total comprehensive (loss) income									$ (38,553)	$ (22,182)	$ (31,225)

Condensed Consolidating Finan92

Condensed Consolidating Financial Information - Guarantor Subsidiaries - Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	$ (19,103)	[1]	$ (564)	$ 133,918
Investing activities:
Purchase of property and equipment	(56,757)		(81,842)	(57,123)
Proceeds from asset dispositions	1,296		14,983	5,236
Purchase of short-term investments	(637,980)		(321,453)	(608,649)
Proceeds from sale of short-term investments	862,942		316,543	505,966
Payments of deposits on aircraft	0		(2,249)	(1,273)
Refund of deposits on aircraft	0		0	6,010
Loan to unconsolidated affiliate	0		(1,200)	0
Loan to third party	(824)		0	0
Business acquisitions net of cash acquired	(126,644)		0	0
Net cash used in investing activities	42,033		(75,218)	(149,833)
Financing activities:
Repurchase of common stock	(256)		(529)	(2,448)
Proceeds from line of credit	152,150		264,700	232,660
Payments on line of credit	(168,650)		(188,200)	(218,160)
Due to/from affiliate, net	0		0	0
Net cash provided by financing activities	(16,756)		75,971	12,052
(Decrease) increase in cash	6,174		189	(3,863)
Cash, beginning of year	2,596		2,407	6,270
Cash, end of year	8,770		2,596	2,407
Parent Company Only (issuer) [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	(62,581)		(46,738)	60,241
Investing activities:
Purchase of property and equipment	(56,757)		(81,484)	(57,123)
Proceeds from asset dispositions	1,296		14,983	5,236
Purchase of short-term investments	(637,980)		(321,453)	(608,649)
Proceeds from sale of short-term investments	862,942		316,543	505,966
Payments of deposits on aircraft	0		(2,249)	(1,273)
Refund of deposits on aircraft				6,010
Loan to unconsolidated affiliate	0		(1,200)
Loan to third party	(824)
Business acquisitions net of cash acquired	(130,788)
Net cash used in investing activities	37,889		(74,860)	(149,833)
Financing activities:
Repurchase of common stock	(256)		(529)	(2,448)
Proceeds from line of credit	152,150		264,700	232,660
Payments on line of credit	(168,650)		(188,200)	(218,160)
Due to/from affiliate, net	41,459		45,617	77,535
Net cash provided by financing activities	24,703		121,588	89,587
(Decrease) increase in cash	11		(10)	(5)
Cash, beginning of year	36		46	51
Cash, end of year	47		36	46
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	40,628		52,873	78,507
Investing activities:
Purchase of property and equipment	0
Net cash used in investing activities	0		0	0
Financing activities:
Due to/from affiliate, net	(41,656)		(52,445)	(82,801)
Net cash provided by financing activities	(41,656)		(52,445)	(82,801)
(Decrease) increase in cash	(1,028)		428	(4,294)
Cash, beginning of year	2,100		1,672	5,966
Cash, end of year	1,072		2,100	1,672
Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	2,850		(6,699)	(4,830)
Investing activities:
Purchase of property and equipment			(358)
Business acquisitions net of cash acquired	4,144
Net cash used in investing activities	4,144		(358)	0
Financing activities:
Due to/from affiliate, net	197		6,828	5,266
Net cash provided by financing activities	197		6,828	5,266
(Decrease) increase in cash	7,191		(229)	436
Cash, beginning of year	460		689	253
Cash, end of year	7,651		460	689
Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash (used in) provided by operating activities	0		0	0
Investing activities:
Net cash used in investing activities	0		0	0
Financing activities:
Net cash provided by financing activities	0		0	0
(Decrease) increase in cash	0		0	0
Cash, beginning of year	0		0	0
Cash, end of year	$ 0		$ 0	$ 0
[1]	Net of the effect of business acquisitions.

Schedule II - Valuation and Q93

Schedule II - Valuation and Qualifying Consolidated Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 6,021	$ 5,151	$ 1,351
Additions Charged to Costs and Expenses	1,218	870	3,800
Deductions	0	0	0
Balance at End of Year	7,239	6,021	5,151
Inventory Valuation Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	17,305	15,385	13,517
Additions Charged to Costs and Expenses	3,570	1,920	1,868
Deductions	0	0	0
Balance at End of Year	20,875	17,305	15,385
Allowance for Contractual Discounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	111,856	103,601	96,590
Additions Charged to Costs and Expenses	480,645	483,449	439,991
Deductions	474,719	475,194	432,980
Balance at End of Year	117,782	111,856	103,601
Allowance for Uncompensated Care [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	46,310	41,924	41,858
Additions Charged to Costs and Expenses	78,883	88,787	84,470
Deductions	72,678	84,401	84,404
Balance at End of Year	$ 52,515	$ 46,310	$ 41,924