Davey Tree Expert 10-K 11 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 08, 2019
Document and Entity Information [Abstract]
Entity registrant name	DAVEY TREE EXPERT CO
Entity central index key	0000277638
Current fiscal year end date	--12-31
Entity filer category	Accelerated Filer
Document type	10-K
Document period end date	Dec. 31, 2018
Document fiscal year focus	2018
Document fiscal period focus	FY
Amendment flag	false
Entity common stock, shares outstanding		22,922,773
Entity well-known seasoned issuer	No
Entity voluntary filers	No
Entity current reporting status	Yes
Entity public float	$ 417,618,382

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash	$ 22,661	$ 13,121
Accounts receivable, net	195,906	168,671
Operating supplies	14,415	10,069
Prepaid expenses	19,529	15,893
Other current assets	2,557	1,371
Total current assets	255,068	209,125
Property and equipment:
Land and land improvements	17,350	18,215
Buildings and leasehold improvements	40,585	40,285
Equipment	581,461	557,536
Property and equipment	639,396	616,036
Less accumulated depreciation	437,111	422,853
Total property and equipment, net	202,285	193,183
Other assets	21,769	29,156
Intangible Assets, Net (Excluding Goodwill)	9,530	6,194
Goodwill	37,971	35,477
Total assets	526,623	473,135
Current liabilities:
Current portion of long-term debt and short-term debt	22,514	16,315
Current portion of capital leases	1,345	651
Accounts payable	43,958	45,093
Accrued expenses	44,061	42,816
Self-insurance accruals	27,434	23,782
Total current liabilities	139,312	128,657
Long-term debt	99,683	105,469
Senior unsecured notes	55,880	11,882
Capital leases	2,862	1,859
Self-insurance accruals	56,351	43,912
Other liabilities	10,125	19,966
Total liabilities	364,213	311,745
Redeemable common shares related to 401KSOP and Employee Stock Ownership Plan (ESOP): 5,642 and 6,467 shares at redemption value as of December 31, 2018 and 2017	119,049	123,520
Common shareholders' equity:
Common shares, $1.00 par value, per share; 48,000 shares authorized; 37,272 and 36,447 shares issued and outstanding before deducting treasury shares and which excludes 5,642 and 6,467 shares subject to redemption as of December 31, 2018 and 2017	37,272	36,447
Additional paid-in capital	82,623	58,554
Common shares subscribed	6,799	7,529
Retained earnings	157,472	143,835
Accumulated other comprehensive loss	(5,034)	(8,393)
Stockholders' equity before treasury stock	279,132	237,972
Less: Cost of Common shares held in treasury; 20,033 shares in 2018 and 18,693 in 2017	235,042	198,327
Common shares subscription receivable	729	1,775
Total common shareholders' equity	43,361	37,870
Total liabilities and shareholders' equity	$ 526,623	$ 473,135

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical)	12 Months Ended
	Dec. 31, 2018$ / sharesshares	Dec. 31, 2017$ / sharesshares
Stock split, conversion ratio	2
Common stock, par value (in dollars per share) | $ / shares	$ 1	$ 1
Common stock, shares authorized	48,000,000	48,000,000
Redeemable stock, outstanding	5,642,154	6,467,027
Common stock, shares issued	37,271,606	36,446,890
Common stock, shares outstanding	37,272,000	36,447,000
Treasury stock, shares	20,033,108	18,692,901

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 1,024,791	$ 915,958	$ 845,678
Costs and expenses:
Operating	665,388	587,333	541,486
Selling	184,388	167,934	152,106
General and administrative	67,462	59,403	58,293
Depreciation	54,914	50,702	47,284
Amortization of intangible assets	2,055	2,384	2,306
Gain on sale of assets, net	(5,106)	(3,989)	(4,664)
Costs and expenses	969,101	863,767	796,811
Income from operations	55,690	52,191	48,867
Other income (expense):
Interest expense	(7,039)	(4,886)	(4,393)
Interest income	350	292	255
Other	(11,505)	(9,603)	(7,485)
Income before income taxes	37,496	37,994	37,244
Income taxes	9,519	15,874	14,960
Net income	$ 27,977	$ 22,120	$ 22,284
Share data:
Earnings per share--basic	$ 1.15	$ 0.87	$ 0.85
Earnings per share--diluted	$ 1.10	$ 0.83	$ 0.82
Weighted-average shares outstanding:
Basic	24,388,738	25,557,468	26,212,040
Diluted	25,480,618	26,697,062	27,247,354
Dividends declared per share	$ 0.100	$ 0.100	$ 0.100

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical)	12 Months Ended
	Dec. 31, 2018
Income Statement [Abstract]
Stock split, conversion ratio	2

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 27,977	$ 22,120	$ 22,284
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments gains/(losses)	(2,514)	2,195	744
Defined benefit pension plans:
Net loss arising during the year	(273)	(1,286)	(1,219)
Amortization of defined benefit pension items:
Net actuarial loss	6,084	2,822	1,912
Prior service cost	62	38	(205)
Amortization of defined benefit pension items:	6,146	2,860	1,707
Defined benefit pension plan adjustments	(5,873)	(1,574)	(488)
Total other comprehensive income, net of tax	3,359	3,769	1,232
Comprehensive income	$ 31,336	$ 25,889	$ 23,516

Statements of Consolidated Shar

Statements of Consolidated Shareholders' Equity - USD ($) $ in Thousands	Total	Common shares	Additional paid-in capital	Common shares subscribed, unissued	Retained earnings	Accumulated other comprehensive income (loss), net of tax	Common shares held in treasury	Common shares subscription receivable
Common shares, at beginning of year at Dec. 31, 2015		35,141,000
Balance at beginning of year, value at Dec. 31, 2015		$ 35,141	$ 24,340	$ 8,591	$ 123,307		$ (159,429)	$ 4,106
Increase (decrease) in stockholders' equity [Roll Forward]
Reclassifications of temporary to permanent equity, shares		716,000
Reclassifications of temporary to permanent equity, value		$ 716
Share subscriptions, beginning balance, shares at Dec. 31, 2015				(872,000)				(872,000)
Balance at beginning of year, shares at Dec. 31, 2015							17,427,000
Balance at the beginning of the year at Dec. 31, 2015	$ (13,394)					$ (13,394)
Increase (decrease) in stockholders' equity [Roll Forward]
Shares purchased, value							$ (25,290)
Shares sold to employees, value			4,182				5,298
Options exercised, value			(992)				(2,442)
Subscription shares, issued, value			(21)				$ 449
Stock-based compensation			2,860
Change in common shares related to 401KSOP and ESOP related shares					(9,043)
Adjustments to additional paid in capital, other			11,215		0
Common shares, issued, value				$ (325)				$ (1,104)
Common shares, issued, shares				(32,000)				(32,000)
Cancellations, value				$ (57)				$ (29)
Cancellations, shares				(6,000)				(6,000)
Net income	22,284				22,284
Dividends					(2,597)
Currency translation adjustments						744
Defined benefit pension plans	(488)					488
Shares purchased, shares							1,492,000
Shares sold							(617,000)
Options exercised, shares							(262,000)
Subscription shares, issued, shares							(49,000)
Balance at ending of year, value at Dec. 31, 2016	$ 27,978	$ 35,857	41,626	$ 8,209	133,951		$ (176,530)	$ 2,973
Share subscriptions, ending balance, shares at Dec. 31, 2016				(834,000)				(834,000)
Balance at ending of year, shares at Dec. 31, 2016	17,866,000						17,991,000
Balance at the end of the year at Dec. 31, 2016	$ (12,162)					(12,162)
Common shares, at end of year at Dec. 31, 2016	35,856,856	35,857,000
Increase (decrease) in stockholders' equity [Roll Forward]
Reclassifications of temporary to permanent equity, shares		590,000
Reclassifications of temporary to permanent equity, value		$ 590
Shares purchased, value							$ (30,566)
Shares sold to employees, value			5,690				5,206
Options exercised, value			76				(2,634)
Subscription shares, issued, value			(35)				$ 929
Stock-based compensation			1,220
Change in common shares related to 401KSOP and ESOP related shares					(9,885)
Adjustments to additional paid in capital, other			9,977		162
Common shares, issued, value				$ (567)				$ (1,123)
Common shares, issued, shares				(59,000)				(59,000)
Cancellations, value				$ (113)				$ (75)
Cancellations, shares				(11,000)				(11,000)
Net income	$ 22,120				22,120
Dividends					(2,513)
Currency translation adjustments						2,196
Defined benefit pension plans	$ (1,574)					1,573
Shares purchased, shares	1,697,727						1,698,000
Shares sold	(662,806)						(663,000)
Options exercised, shares							(242,000)
Subscription shares, issued, shares							(91,000)
Balance at ending of year, value at Dec. 31, 2017	$ 37,870	$ 36,447	58,554	$ 7,529	143,835		$ (198,327)	$ 1,775
Share subscriptions, ending balance, shares at Dec. 31, 2017				(764,000)				(764,000)
Balance at ending of year, shares at Dec. 31, 2017	17,754,000						18,693,000
Balance at the end of the year at Dec. 31, 2017	$ (8,393)					(8,393)
Common shares, at end of year at Dec. 31, 2017	36,446,890	36,447,000
Increase (decrease) in stockholders' equity [Roll Forward]
Reclassifications of temporary to permanent equity, shares		825,000
Reclassifications of temporary to permanent equity, value		$ 825
Shares purchased, value							$ (51,116)
Shares sold to employees, value			6,820				10,617
Options exercised, value			145				(2,326)
Subscription shares, issued, value			(99)				$ 1,458
Stock-based compensation			1,958
Change in common shares related to 401KSOP and ESOP related shares					(11,598)
Adjustments to additional paid in capital, other			15,245		(355)
Common shares, subscribed, value	$ (12,563)
Common shares, subscribed, shares	(1,275,428)
Common shares, issued, value				$ (543)				$ (1,005)
Common shares, issued, shares				(55,000)				(55,000)
Cancellations, value				$ (187)				$ (41)
Cancellations, shares				(19,000)				(19,000)
Net income	$ 27,977				27,977
Dividends					(2,387)
Currency translation adjustments						(2,514)
Defined benefit pension plans	$ (5,873)					5,873
Shares purchased, shares	2,636,943						2,637,000
Shares sold	(960,740)						(961,000)
Options exercised, shares							(207,000)
Subscription shares, issued, shares							(129,000)
Balance at ending of year, value at Dec. 31, 2018	$ 43,361	$ 37,272	$ 82,623	$ 6,799	$ 157,472		$ (235,042)	$ 729
Share subscriptions, ending balance, shares at Dec. 31, 2018				(690,000)				(690,000)
Balance at ending of year, shares at Dec. 31, 2018	17,239,000						20,033,000
Balance at the end of the year at Dec. 31, 2018	$ (5,034)					$ (5,034)
Common shares, at end of year at Dec. 31, 2018	37,271,606	37,272,000

Statement of Consolidated Share

Statement of Consolidated Shareholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2018$ / shares	Dec. 31, 2017$ / shares	Dec. 31, 2016$ / shares
Dividends declared per share	$ 0.100	$ 0.100	$ 0.100
Stock split, conversion ratio	2

Consolidated Statements of Cash

Consolidated Statements of Cash Flow - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net income	$ 27,977	$ 22,120	$ 22,284
Adjustments to reconcile net income to net cash provided by operating activities net of assets/liabilities acquired:
Depreciation	54,914	50,702	47,284
Amortization	2,055	2,384	2,306
Gain on sale of assets	(5,106)	(3,989)	(4,664)
Deferred income taxes	4,014	3,753	60
Other	134	2,581	1,286
Changes in operating assets and liabilities:
Accounts receivable	(26,829)	(20,784)	(26,133)
Accounts payable and accrued expenses	(1,970)	6,164	2,454
Self-insurance accruals	16,091	4,856	2,499
Other assets, net	(9,176)	(11,011)	7,994
Adjustments to reconcile net income to net cash provided by operating activities	34,127	34,656	33,086
Net cash provided by operating activities	62,104	56,776	55,370
Capital expenditures:
Equipment	(58,620)	(53,128)	(54,147)
Land and buildings	(1,790)	(3,972)	(2,499)
Proceeds from sales of property and equipment	7,494	5,034	5,635
Purchases of businesses, net of cash acquired	(8,461)	(7,452)	(3,797)
Net cash used in investing activities	(61,377)	(59,518)	(54,808)
Financing activities
Revolving credit facility borrowings	507,500	328,000	252,500
Revolving credit facility payments	(514,000)	(295,000)	(240,000)
Proceeds from notes payable	74,716	16,610	17,832
Payments of notes payable	(26,339)	(23,008)	(20,638)
Payments of capital leases	(891)	(2,294)	(1,680)
Purchase of common shares for treasury	(51,116)	(30,404)	(25,290)
Sale of common shares from treasury	20,536	13,820	11,019
Cash received on common-share subscriptions	1,046	1,199	1,133
Dividends	(2,387)	(2,513)	(2,597)
Net cash provided by (used in) financing activities	9,065	6,410	(7,721)
Effect of exchange rate changes on cash	(252)	447	135
Increase (Decrease) in cash	9,540	4,115	(7,024)
Cash, beginning of year	13,121	9,006	16,030
Cash, end of year	$ 22,661	$ 13,121	$ 9,006

Our Business

Our Business	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Our Business	Our Business We provide a wide range of arboricultural, horticultural, environmental and consulting services to residential, utility, commercial and government entities throughout the United States and Canada. We have two reportable operating segments organized by type or class of customer: Residential and Commercial, and Utility. Residential and Commercial --Residential and Commercial provides services to our residential and commercial customers including: the treatment, preservation, maintenance, removal and planting of trees, shrubs and other plant life; the practice of landscaping, grounds maintenance, tree surgery, tree feeding and tree spraying; the application of fertilizer, herbicides and insecticides; and, natural resource management and consulting, forestry research and development, and environmental planning. Utility --Utility is principally engaged in providing services to our utility customers--investor-owned, municipal utilities, and rural electric cooperatives--including: the practice of line-clearing and vegetation management around power lines, rights-of-way and chemical brush control; and, natural resource management and consulting, forestry research and development and environmental planning. We also maintain research, technical support and laboratory diagnostic facilities. When we refer to “we,” “us,” “our,” “Davey Tree,” and the “Company,” we mean The Davey Tree Expert Company, unless the context indicates otherwise.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Principles of Consolidation and Basis of Presentation --The consolidated financial statements include the accounts of Davey Tree and our wholly-owned subsidiaries and were prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as codified in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC"). Intercompany accounts and transactions have been eliminated in consolidation. Per Common Share Information --We have given retroactive consideration to the two -for-one stock split of our common shares effective June 1, 2017 including all common share and per share data. Use of Estimates in Financial Statement Preparation --The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect reported amounts. Estimates are used for, but not limited to, accounts receivable valuation, depreciable lives of fixed assets, self-insurance accruals, stock valuation and revenue recognition. Actual results could differ from those estimates. The Company’s fiscal quarters each contain thirteen operating weeks, with the exception of the fourth quarter of a 53-week fiscal year, which contains fourteen operating weeks. Property and Equipment --Property and equipment are stated at cost. Repair and maintenance costs are expensed as incurred. Depreciation is computed for financial reporting purposes by the straight-line method for land improvements, building and leasehold improvements and by the declining-balance method for equipment, based on the estimated useful lives of the assets, as follows: Land improvements 5 to 20 years Buildings 5 to 30 years Equipment 3 to 20 years Leasehold improvements Shorter of lease term or estimated useful life; ranging from 5-to-20 years Intangible Assets --Intangible assets with finite lives, primarily customer lists, noncompete agreements and tradenames, are amortized by the straight-line method based on their estimated useful lives, ranging from one-to-ten years. B. Summary of Significant Accounting Policies (continued) Long-Lived Assets --We assess potential impairment to our long-lived assets, other than goodwill, when there is evidence that events or changes in circumstances have made recovery of the asset’s carrying value unlikely and the carrying amount of the asset exceeds the estimated future undiscounted cash flow. In the event the assessment indicates that the carrying amounts may not be recoverable, an impairment loss would be recognized to reduce the asset’s carrying amount to its estimated fair value based on the present value of the estimated future cash flows. Goodwill --Goodwill is recorded when the cost of acquired businesses exceeds the fair value of the identified net assets acquired. Goodwill is not amortized, but tested for impairment annually or when events or circumstances indicate that impairment may have occurred. Annually, we perform the impairment tests for goodwill during the fourth quarter. Impairment of goodwill is tested at the reporting-unit level, which for us are also our business segments. Impairment of goodwill is tested by comparing the reporting unit’s carrying value, including goodwill, to the fair value of the reporting unit. The fair values of the reporting units are estimated using discounted projected cash flows. If the carrying value of the reporting unit exceeds its fair value, goodwill is considered impaired and an impairment loss should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the carrying value of the goodwill allocated to that reporting unit. We conducted our annual impairment tests and determined that no impairment loss was required to be recognized in 2018 or for any prior periods. There were no events or circumstances from the date of our assessment through December 31, 2018 that would impact this conclusion. Self-Insurance Accruals --We are generally self-insured for losses and liabilities related primarily to workers’ compensation, vehicle liability and general liability claims. We use commercial insurance as a risk-reduction strategy to minimize catastrophic losses. Ultimate losses are accrued based upon estimates of the aggregate liability for claims incurred using certain actuarial assumptions followed in the insurance industry and based on Company-specific experience. Our self-insurance accruals include claims for which the ultimate losses will develop over a period of years. Accordingly, our estimates of ultimate losses can change as claims mature. Our accruals also are affected by changes in the number of new claims incurred and claim severity. The methods for estimating the ultimate losses and the total cost of claims were determined by third-party consulting actuaries; the resulting accruals are reviewed by management, and any adjustments arising from changes in estimates are reflected in income. The workers' compensation accruals are discounted as the amount and timing of cash payments related to those accruals are reliably determinable given the nature of workers' compensation benefits and the level of historical claim volume to support the actuarial assumptions and judgments used to derive the expected loss payment pattern. The workers' compensation accruals are discounted using an interest rate that approximates the long-term investment yields over the expected payment pattern of unpaid losses. Our self-insurance accruals are based on estimates and, while we believe that the amounts accrued are adequate and not excessive, the ultimate claims may be in excess of or less than the amounts provided. Stock-Based Compensation -- Stock-based compensation cost for all share-based payment plans is measured at fair value on the date of grant and recognized over the employee service period on the straight-line recognition method for awards expected to vest. The fair value of all stock-based payment plans—stock option plans, stock-settled stock appreciation rights, and performance-based restricted stock units as well as our Employee Stock Purchase Plan—is determined by the number of awards granted and the price of our common stock. The fair value of each award is estimated on the date of grant using a binomial option-pricing model. The binomial model considers a range of assumptions related to volatility, risk-free interest rate and employee exercise behavior. Expected volatilities utilized in the binomial model are based on historical volatility of our share prices and other factors. Similarly, the dividend yield is based on historical experience and expected future changes. The binomial model also incorporates exercise assumptions based on an analysis of historical data. The expected life of the stock-based awards is derived from the output of the binomial model and represents the period of time that awards granted are expected to be outstanding. Defined Benefit Pension Plans --We record annual expenses relating to our defined benefit pension plans based on calculations that include various actuarial assumptions, including discount rates and expected long-term rates of return on plan assets. Actuarial assumptions are reviewed annually with modifications made to the assumptions, if necessary, based on B. Summary of Significant Accounting Policies (continued) current rates and trends. The effects of the actuarial gains or losses are amortized over future service periods. The funded status (that is, the projected benefit obligation less the fair value of plan assets) for each plan is reported in our balance sheet using a December 31 measurement date. Changes in the funded status of the plans are recognized in the year in which the changes occur and reported in comprehensive income (loss). Income Taxes --We compute taxes on income in accordance with the tax rules and regulations where the income is earned. The income tax rates imposed by these taxing authorities vary. Taxable income may differ from pretax income for financial reporting purposes. We compute and recognize deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amounts and the tax bases of our assets and liabilities. Changes in tax rates and laws are reflected in income in the period when such changes are enacted. We account for uncertain tax positions by recognizing the financial statement effects of a tax position only when, based upon the technical merits, it is more-likely-than-not that the position will be sustained upon examination. Earnings Per Share --Basic earnings per share is determined by dividing the income available to common shareholders by the weighted-average number of common shares outstanding. Diluted earnings per share is computed similarly to basic earnings per share except that the weighted-average number of shares is increased to include the effect of stock awards that were granted and outstanding during the period. Revenue Recognition --We recognize revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers, which we adopted on January 1, 2018, using the modified retrospective method. See Note C for further discussion of the adoption, including the impact on our 2018 financial statements. Performance obligations are satisfied as our services are provided to customers. See Note T for a detailed description of our revenue recognition policy. Concentration of Credit Risk --Credit risk represents the accounting loss that would be recognized if the counterparties failed to perform as contracted. The principal financial instruments subject to credit risk follow: Cash --To limit our exposure, we transact our business and maintain banking relationships with high credit-quality financial institutions. Accounts Receivable --Our residential and commercial customers are located geographically throughout the United States and Canada and, as to commercial customers, within differing industries; thus, minimizing credit risk. The credit exposure of utility services customers is directly affected by conditions within the utility industries as well as the financial condition of individual customers. One utility customer approximated 12% of revenues during 2018 , 11% in 2017 and 12% in 2016 . To reduce credit risk, we evaluate the credit of customers, but generally do not require advance payments or collateral. Exposure to losses on receivables is principally dependent on each customer’s financial condition. Foreign Currency Translation and Transactions --Assets and liabilities of our Canadian operations are translated into U.S. dollars using year-end exchange rates, and revenues and expenses are translated using exchange rates as determined throughout the year. Gains or losses resulting from translation are included in the consolidated balance sheet, classified in shareholders’ equity as a separate component of accumulated other comprehensive income (loss). Gains or losses resulting from Canadian-dollar transactions with the Canadian operations are converted to U.S. dollars at the rates of exchange prevailing at the dates of the transactions. The effect of the transactions gain or loss is classified in the statement of operations as a component of other nonoperating income (expense), net. Interest Rate Risk Management --We have entered into interest rate contracts, from time-to-time, with the objective of altering interest rate exposures related to variable rate debt. In the interest rate contracts, we have agreed with a financial institution to exchange, at specified intervals, the difference between fixed and floating interest amounts calculated on an agreed-upon notional principal amount. During the year ended December 31, 2018, we did not enter into any interest rate contracts. B. Summary of Significant Accounting Policies (continued) Comprehensive Income (Loss) --Comprehensive income (loss) includes net income and other comprehensive income or loss. Other comprehensive income (loss) refers to revenues, expenses, gains and losses that under U.S. GAAP are included in comprehensive income but are excluded from net income as these amounts are recorded directly as an adjustment to shareholders’ equity, net of tax.

Recent Accounting Guidance

Recent Accounting Guidance	12 Months Ended
	Dec. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Guidance	Recent Accounting Guidance Accounting Standards Adopted in 2018 Accounting Standards Update 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business --In January 2017, the FASB issued Accounting Standard Update ("ASU") 2017-01, "Business Combinations (Topic 805): Clarifying the Definition of a Business," which provides guidance to evaluate whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. If substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single asset or a group of similar assets, the assets acquired (or disposed of) are not considered a business. The Company adopted the guidance effective January 1, 2018. ASU 2017-01 applies prospectively for annual and interim periods beginning after December 15, 2017. The adoption of this guidance did not have a material impact on our consolidated financial statements. Accounting Standards Update 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the FASB Emerging Issues Task Force) --In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments,” which provides guidance on how cash receipts and cash payments related to eight specific cash flow issues are presented and classified in the statement of cash flows, with the objective of reducing the existing diversity in practice. The Company adopted ASU 2016-15 prospectively on January 1, 2018. The adoption of ASU 2016-15 did not have a material impact on our consolidated financial statements. Accounting Standards Update 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost --In March 2017, the FASB issued ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost,” which changes the presentation of net periodic benefit cost related to employer sponsored defined benefit plans and other postretirement benefits. Under ASU 2017-07, service costs are included within the same income statement line item as other compensation costs arising from services rendered by pertinent employees during the period. The other components of net periodic benefit pension cost are presented separately outside of income from operations. Additionally, only the service cost component of the net periodic benefit cost may be capitalized in assets. The amendments under ASU 2017-07 also provide a practical expedient that permits the use of amounts disclosed in the pension and other postretirement benefit plan footnote for prior year comparative periods as the estimation basis for applying the guidance retrospectively. The Company adopted ASU 2017-07 on January 1, 2018 and chose to use the practical expedient provided when applying the guidance retrospectively. Upon adoption, service costs are recognized in our financial statements as general and administrative expenses while the remaining components of net periodic benefit cost are recognized as other income (expense). Pension expense of $5,186 for the year ended December 31, 2017 and $3,496 for the year ended December 31, 2016 have been reclassified from general and administrative expense to other income (expense). Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606 )--In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606),” which replaces all current U.S. GAAP guidance on revenue recognition and eliminates all industry-specific guidance. The Company adopted ASU 2014-09 and applied it to all contracts that were not completed as of January 1, 2018 using the modified retrospective method. The cumulative effect of applying the guidance in ASU 2014-09 was not material. Further, the adoption of ASU 2014-09 did not have a significant impact on the amount or timing of revenue recognition. Therefore, we have not disclosed the amount by which each financial statement line item is affected in the current period as a result of applying ASU 2014-09 or an explanation of significant changes between our results as reported and those that would have been reported under legacy U.S. GAAP, as no significant changes were identified. C. Recent Accounting Guidance (continued) Accounting Standards Not Yet Adopted Accounting Standards Update 2016-02, Leases (Topic 842) --In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842).” The FASB issued subsequent amendments to the initial guidance in July 2018 with ASU 2018-10, in August 2018 with ASU 2018-11, and in December 2018 with ASU 2018-20. ASU 2016-02 establishes a comprehensive new lease accounting model. The new standard: (a) clarifies the definition of a lease; (b) requires a dual approach to lease classification similar to current lease classifications; and (c) causes lessees to recognize leases on the balance sheet as a lease liability with a corresponding right-of-use asset for leases with a lease-term of more than twelve months. The new standard is effective for interim and annual periods beginning after December 15, 2018, which for Davey Tree would be January 1, 2019. Management has evaluated all real estate, personal property and other arrangements that may meet the definition of a lease and has implemented a technology solution to assist with the management of leases. We will adopt the new standard on the required effective date of January 1, 2019 using the Comparatives Under ASC 840 approach, which requires application of the new guidance at the beginning of the standard’s effective date. The Company elected the Package of Three practical expedient and has decided not to elect the “Hindsight” practical expedient. As a result, the Company will measure the right of use asset and lease liability for operating leases upon adoption using the remaining portion of the lease term that was determined under ASC 840 when the lease was entered into. A cross-functional implementation team is finalizing policy elections, the discount rate to be used based on January 1, 2019 data, and business processes and controls to support recognition and disclosure under the new standard. The primary impact upon adoption will be the recognition of right of use assets and lease liabilities, on a discounted basis, of our minimum lease obligations, as disclosed in Note K. We currently do not expect ASU 2016-02 to have a material effect on our Consolidated Statements of Income. Accounting Standards Update 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) --In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220)." ASU 2018-02 provides an option to reclassify the stranded tax effects within accumulated other comprehensive income to retained earnings as a result of the Tax Cuts and Jobs Act of 2017 (the "Tax Reform Act"). This standard is effective for interim and annual reporting periods beginning after December 15, 2018, which for Davey Tree would be January 1, 2019. Early adoption is permitted. Management has not yet completed its assessment of the impact of the new standard on the Company's consolidated financial statements. SEC Release No. 33-10532, Disclosure Update and Simplification --In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of shareholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of shareholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. This final rule is effective for all filings made on or after November 5, 2018. Given the effective date and the proximity to most filers' quarterly reports, the SEC is not objecting to filers deferring the presentation of changes in shareholders' equity in their Forms 10-Q until the quarter that begins after the date of adoption, November 5, 2018. We plan to present the interim changes in shareholders' equity required by SEC Release No. 33-10532 beginning with our first quarter 2019 Form 10-Q.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Business Combinations	Business Combinations Our investments in businesses were: (a) $13,244 in 2018 , including liabilities assumed of $2,381 and debt issued of $2,402 ; (b) $13,264 in 2017 , including liabilities assumed of $2,713 and debt issued of $3,099 ; and (c) $4,888 in 2016 , including $216 of liabilities assumed and debt issued of $875 . The net assets of the businesses acquired are accounted for under the acquisition method and were recorded at their fair values at the dates of acquisition. The measurement period for purchase price allocations ends as soon as information of the D. Business Combinations (continued) facts and circumstances becomes available, but does not exceed one year from the acquisition date. On November 30, 2018, we finalized the acquisition of Kerr Environmental, for which purchase accounting entries related to fixed assets, intangible assets and goodwill have not yet been finalized as of December 31, 2018. The Company’s intangible assets consist of tradenames, non-competition agreements and customer relationships. The tradenames and customer relationships intangible assets were assigned an average seven -year useful life, and the non-competition agreements were assigned an average five -year useful life. The excess of the purchase price over the estimated fair values of the net assets acquired was recorded as an increase in goodwill of approximately $2,840 in 2018 (all of which is deductible for tax purposes), $5,131 in 2017 (all of which is deductible for tax purposes) and $817 goodwill in 2016 (all of which is deductible for tax purposes). The results of operations of acquired businesses have been included in the consolidated statements of operations beginning as of the effective dates of acquisition. The effect of these acquisitions on our consolidated revenues and results of operations, either individually or in the aggregate, for the years ended December 31, 2018 , 2017 or 2016 was not significant.

Accounts Receivable, Net and Su

Accounts Receivable, Net and Supplemental Balance Sheet Information	12 Months Ended
	Dec. 31, 2018
Accounts Receivable, Net and Supplemental Balance Sheet Information [Abstract]
Accounts Receivable, Net and Supplemental Balance Sheet Information	Accounts Receivable, Net and Supplemental Balance Sheet Information Accounts receivable, net, consisted of the following: December 31, 2018 2017 Accounts receivable $ 158,556 $ 143,244 Unbilled receivables 40,671 29,895 199,227 173,139 Less allowances for doubtful accounts 3,321 4,468 $ 195,906 $ 168,671 Unbilled Receivables consist of work-in-process in accordance with the terms of contracts, primarily, with utility services customers. The following items comprise the amounts included in the balance sheets: December 31, Other current assets 2018 2017 Refundable income taxes $ 1,625 $ 587 Other 932 784 Total $ 2,557 $ 1,371 December 31, Other assets, noncurrent 2018 2017 Assets invested for self-insurance $ 15,379 $ 19,422 Investment--cost-method affiliate 1,218 1,218 Deferred income taxes 573 4,815 Other 4,599 3,701 Total $ 21,769 $ 29,156 E. Accounts Receivable, Net and Supplemental Balance Sheet Information (continued) December 31, Accrued expenses 2018 2017 Employee compensation $ 24,086 $ 20,794 Accrued compensated absences 9,711 9,267 Self-insured medical claims 3,343 3,193 Customer advances, deposits 1,322 1,672 Income taxes payable 31 3,443 Taxes, other than income 2,546 2,279 Other 3,022 2,168 Total $ 44,061 $ 42,816 December 31, Other liabilities, noncurrent 2018 2017 Pension and retirement plans $ 6,138 $ 14,759 Other 3,987 5,207 Total $ 10,125 $ 19,966

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Supplemental cash flow information follows: Year Ended December 31, Supplemental cash flow information 2018 2017 2016 Interest paid $ 6,375 $ 5,096 $ 4,329 Income taxes paid, net 11,514 10,005 10,578 Noncash transactions: Debt issued for purchases of businesses $ 2,402 $ 3,099 $ 875 Detail of acquisitions: Assets acquired: Accounts receivable $ 1,311 $ 1,753 $ — Operating supplies 23 — 157 Prepaid expense 89 128 55 Equipment 4,079 1,904 2,485 Other assets 7 52 — Intangible assets 4,895 4,296 1,374 Goodwill 2,840 5,131 817 Liabilities assumed (2,381 ) (2,713 ) (216 ) Debt issued for purchases of businesses (2,402 ) (3,099 ) (875 ) Cash paid $ 8,461 $ 7,452 $ 3,797

Identified Intangible Assets an

Identified Intangible Assets and Goodwill, Net	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Identified Intangible Assets and Goodwill, Net [Text Block]	Intangible Assets and Goodwill, Net The carrying amount of the intangible assets and goodwill acquired in connection with our acquisitions were as follows: Weighted-Average Amortization Period (Years) December 31, 2018 December 31, 2017 Carrying Amount Accumulated Amortization Carrying Amount Accumulated Amortization Amortized intangible assets: Customer lists/relationships 3.6 years $ 25,179 $ 18,251 $ 21,487 $ 16,846 Employment-related 2.8 years 8,133 6,954 7,333 6,624 Tradenames 3.7 years 6,858 5,435 5,978 5,134 Total 40,170 $ 30,640 34,798 $ 28,604 Less accumulated amortization 30,640 28,604 Intangible assets, net 9,530 6,194 Goodwill 37,971 35,477 $ 47,501 $ 41,671 The changes in the carrying amounts of goodwill, by segment, for the years ended December 31, 2018 and December 31, 2017 follow: Balance at January 1, 2018 Acquisitions Translation and Other Adjustments Balance at December 31, 2018 Utility $ 3,424 $ 1,487 $ — $ 4,911 Residential and Commercial 32,053 1,353 (346 ) 33,060 Total $ 35,477 $ 2,840 $ (346 ) $ 37,971 Balance at January 1, 2017 Acquisitions Translation and Other Adjustments Balance at December 31, 2017 Utility $ 3,424 $ — $ — $ 3,424 Residential and Commercial 26,881 5,131 41 32,053 Total $ 30,305 $ 5,131 $ 41 $ 35,477 Estimated future aggregate amortization expense of intangible assets -- The estimated aggregate amortization expense of intangible assets, as of December 31, 2018 , in each of the next five years follows: Estimated Future Amortization Expense Year ending December 31, 2019 $ 2,197 2020 2,011 2021 1,569 2022 1,339 2023 1,209 Thereafter 1,205 $ 9,530

Short and Long-Term Debt and Co

Short and Long-Term Debt and Commitments Related to Letters of Credit	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Short and Long-Term Debt and Commitments Related to Letters of Credit [Text Block]	Short and Long-Term Debt and Commitments Related to Letters of Credit Short-term debt consisted of the following: December 31, 2018 2017 Notes payable $ — $ 149 Current portion of long-term debt 22,514 16,166 $ 22,514 $ 16,315 At December 31, 2018 , we also had unused short-term lines of credit with several banks totaling $7,097 , generally at the banks' prime rate or LIBOR plus a margin adjustment of .75% to 1.50% . Long-term debt consisted of the following: December 31, 2018 2017 Revolving credit facility Swing-line borrowings $ 2,500 $ — LIBOR borrowings 91,000 100,000 93,500 100,000 5.09% Senior unsecured notes 12,000 18,000 3.99% Senior unsecured notes 50,000 — Term loans 23,176 16,242 178,676 134,242 Less debt issuance costs 599 725 Less current portion 22,514 16,166 $ 155,563 $ 117,351 Revolving Credit Facility and Senior Unsecured Notes -- In October 2017, the Company amended and restated its revolving credit facility, as further amended in September 2018, as discussed below. The amended and restated credit agreement, which expires in October 2022, permits borrowings as defined up to $250,000 including a letter of credit sublimit of $100,000 and a swing-line commitment of $25,000 . Under certain circumstances, the amount available under the revolving credit facility may be increased to $325,000 . The revolving credit facility contains certain affirmative and negative covenants customary for this type of facility and includes financial covenant ratios with respect to a maximum leverage ratio (not to exceed 3.00 to 1.00 with exceptions in case of material acquisitions) and a minimum interest coverage ratio (not less than 3.00 to 1.00), in each case subject to certain further restrictions as described in the Credit Agreement. On July 22, 2010, we issued $30,000 of 5.09% Senior Unsecured Notes, Series A, due July 22, 2020 (the " 5.09% Senior Notes"). The 5.09% Senior Notes were issued pursuant to a Master Note Purchase Agreement (the “Purchase Agreement”), between the Company and the purchasers of the 5.09% Senior Notes. The net proceeds of the 5.09% Senior Notes were used to pay down borrowings under our revolving credit facility. The 5.09% Senior Notes are equal in right of payment with our revolving credit facility and all other senior unsecured obligations of the Company. Interest is payable semiannually and five equal, annual principal payments commenced on July 22, 2016 (the sixth anniversary of issuance). The Purchase Agreement contains customary events of default and covenants related to limitations on indebtedness and transactions with affiliates and the maintenance of certain financial ratios. On September 21, 2018, we issued 3.99 % Senior Notes, Series A (the " 3.99 % Senior Notes"), in the aggregate principal amount of $50,000 . The 3.99 % Senior Notes are due September 21, 2028. The 3.99 % Senior Notes were issued pursuant to a Note Purchase and Private Shelf Agreement (the “Note Purchase and Shelf Agreement”) between the Company, PGIM, Inc. and the purchasers of the 3.99 % Senior Notes. Subsequent series of I. Short and Long-Term Debt and Commitments Related to Letters of Credit (continued) promissory notes may be issued pursuant to the 3.99 % Senior Note Purchase Agreement (the "Shelf Notes") in an aggregate additional principal amount not to exceed $50,000 . The net proceeds of the 3.99 % Senior Notes were used to pay down borrowings under our revolving credit facility. The 3.99 % Senior Notes are equal in right of payment with our revolving credit facility and all other senior unsecured obligations of the Company. Interest is payable semiannually and five equal, annual principal payments of $10,000 commence on September 21, 2024 (the sixth anniversary of issuance). The Note Purchase and Shelf Agreement contains customary events of default and covenants related to limitations on indebtedness and transactions with affiliates and the maintenance of certain financial ratios. The Company may prepay at any time all, or from time to time any part of, the outstanding principal amount of the 3.99 % Senior Notes, subject to the payment of a make-whole amount. In conjunction with the issuance of the 3.99 % Senior Notes, on September 21, 2018, the Company entered into an amendment to its revolving credit facility. The amendment amended certain provisions and covenants in the credit agreement to generally conform them to the corresponding provisions and covenants in the Note Purchase and Shelf Agreement. The amendment also permitted the Company to incur indebtedness arising under the Note Purchase and Shelf Agreement in an aggregate principal amount not to exceed $75,000 , which included the $50,000 of 3.99 % Senior Notes, plus an additional $25,000 in Shelf Notes. As of December 31, 2018 , we had unused commitments under the revolving credit facility approximating $153,377 and $96,623 committed, which consisted of borrowings of $93,500 and issued letters of credit of $3,123 . Borrowings outstanding bear interest, at the Company's option, of either (a) the base rate or (b) LIBOR plus a margin adjustment ranging from .875% to 1.50% --with the margin adjustments in both instances based on the Company's leverage ratio at the time of borrowing. The base rate is the greater of (i) the agent bank’s prime rate, (ii) LIBOR plus 1.5% , or (iii) the federal funds rate plus .5% . A commitment fee ranging from .10% to .225% is also required based on the average daily unborrowed commitment. Term loans --Periodically, the company will enter into term loans for the procurement of insurance or to finance acquisitions. Term Loans, Weighted-Average Interest Rate --The weighted-average interest on the term loans approximated 4.28% at December 31, 2018 and 3.56% at December 31, 2017 . Aggregate Maturities of Long-Term Debt --Aggregate maturities of long-term debt for the five years subsequent to December 31, 2018 were as follows: 2019 -- $22,514 ; 2020 -- $7,569 ; 2021 -- $5,093 ; 2022 -- $93,500 ; 2023 -- $0 ; and thereafter $50,000 . Accounts Receivable Securitization Facility --In May 2018, Davey Tree amended its Accounts Receivable Securitization Facility (the “AR securitization facility”), to extend the scheduled termination date for an additional one -year period, to May 6, 2019. In addition, for purposes of determining events of default, the Days' Sales Outstanding calculation was amended to include the most recent six fiscal months. The prior calculation was based on the most recent three fiscal months. Under the AR Securitization program, Davey Tree transfers by selling or contributing current and future trade receivables to a wholly-owned, bankruptcy-remote financing subsidiary which pledges a perfected first priority security interest in the trade receivables--equal to the issued letters of credit ("LCs") as of December 31, 2018 --to the bank in exchange for the bank issuing LCs. Fees payable to the bank include: (a) an LC issuance fee, payable on each settlement date, in the amount of .90% per annum on the aggregate amount of all LCs outstanding plus outstanding reimbursement obligations (e.g., arising from drawn LCs), if any, and (b) an unused LC fee, payable monthly, equal to (i) .35% per annum for each day on which the sum of the total LCs outstanding plus any outstanding reimbursement obligations is greater than or equal to 50% of the facility limit and (ii) .45% per annum for each day on which the sum of the total LCs outstanding plus any outstanding reimbursement obligations is less than 50% of the facility limit. If an LC is drawn and the bank is not immediately reimbursed in full for the drawn amount, any outstanding reimbursement obligation will accrue interest at a per annum rate equal to a reserve-adjusted LIBOR or, in certain circumstances, a base rate equal to the higher of (i) the bank’s prime rate and (ii) the federal funds rate plus .50% and, I. Short and Long-Term Debt and Commitments Related to Letters of Credit (continued) following any default, 2.00% plus the greater of (a) adjusted LIBOR and (b) a base rate equal to the higher of (i) the bank’s prime rate and (ii) the federal funds rate plus .50% . The agreements underlying the AR securitization facility contains various customary representations and warranties, covenants, and default provisions which provide for the termination and acceleration of the commitments under the AR securitization facility in circumstances including, but not limited to, failure to make payments when due, breach of a representation, warranty or covenant, certain insolvency events or failure to maintain the security interest in the trade receivables, and defaults under other material indebtedness. The AR Securitization program has a limit of $100,000 , of which $67,438 was issued for letters of credit as of December 31, 2018 . Total Commitments Related to Issued Letters of Credit --As of December 31, 2018 , total commitments related to issued letters of credit were $72,565 , of which $3,123 were issued under the revolving credit facility, $67,438 were issued under the AR securitization facility and $2,004 were issued under short-term lines of credit. As of December 31, 2017 , total commitments related to issued letters of credit were $63,242 , of which $3,088 were issued under the revolving credit facility, $58,150 were issued under the AR securitization facility and $2,004 were issued under short-term lines of credit. As of December 31, 2018 , we are in compliance with all debt covenants.

Self-Insurance Accruals

Self-Insurance Accruals	12 Months Ended
	Dec. 31, 2018
Self-Insurance Accruals [Abstract]
Self-Insurance Accruals [Text Block]	Self-Insurance Accruals Components of our self-insurance accruals for workers’ compensation, vehicle liability and general liability follow: December 31, 2018 2017 Workers' compensation $ 41,577 $ 40,764 Present value discount 3,099 2,346 38,478 38,418 Vehicle liability 13,342 5,536 General liability 31,965 23,740 Total 83,785 67,694 Less current portion 27,434 23,782 Noncurrent portion $ 56,351 $ 43,912 The changes in our self-insurance accruals and the discount rate used for the workers’ compensation accrual are summarized in the table below. December 31, 2018 2017 Balance, beginning of year $ 67,694 $ 62,838 Provision for claims 51,685 34,884 Payment of claims (35,594 ) (30,028 ) Balance, end of year $ 83,785 $ 67,694 Workers' compensation discount rate 2.50 % 2.00 % The increase in the provision for claims primarily relates to increases for certain vehicle and general liability claims that are anticipated to settle in the future at or near our retention levels.

Lease Obligations

Lease Obligations	12 Months Ended
	Dec. 31, 2018
Leases [Abstract]
Lease Obligations [Text Block]	Lease Obligations Assets acquired under capital leases and included in property and equipment consisted of the following: December 31, 2018 2017 Equipment $ 6,534 $ 3,481 Less accumulated amortization 1,797 805 $ 4,737 $ 2,676 We also lease facilities under noncancelable operating leases, which are used for district office and warehouse operations and equipment used in operations. These leases extend for varying periods of time up to five years and, in some cases, contain renewal options. Minimum rental commitments under all capital and noncancelable operating leases, as of December 31, 2018 , were as follows: Lease Obligations Minimum lease obligations Capital Operating Year ending December 31, 2019 $ 1,426 $ 14,023 2020 1,371 11,272 2021 1,183 7,712 2022 272 5,129 2023 71 2,060 2024 and after — 1,923 Total minimum lease payments 4,323 $ 42,119 Amounts representing interest 116 Present value of net minimum lease payments 4,207 Less current portion 1,345 Long-term capital lease obligations, December 31, 2018 $ 2,862 Total rent expense under all operating leases was $9,594 in 2018 , $7,998 in 2017 and $7,536 in 2016 .

Common Shares, Redeemable Commo

Common Shares, Redeemable Common Shares and Preferred Shares	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Common Shares, Redeemable Common Shares and Preferred Shares [Text Block]	Common Shares, Redeemable Common Shares and Preferred Shares We have given retroactive consideration to the two -for-one stock split of our common shares effective June 1, 2017 including all common share and per share data. Preferred Shares --We have authorized a class of 4,000,000 preferred shares, no par value, of which none were issued as of December 31, 2018 . Redeemable Common Shares - Our Davey 401KSOP and ESOP Plan includes a put option for shares of the Company’s common stock distributed from the plan. Due to the Company’s obligation under the put option, shares held in the Davey 401KSOP and ESOP Plan as well as distributed shares subject to the put option are reclassified from permanent equity to temporary equity. The number of redeemable common shares for each of the three years in the period ended December 31, 2018 was as follows: 2018-- 5,642,154 ; 2017-- 6,467,027 ; and 2016-- 7,056,904 . Common Shares --The number of common shares authorized is 48,000,000 , par value $1.00 . The number of common shares issued during each of the three years in the period ended December 31, 2018 was as follows: 2018-- 37,271,606 ; 2017-- 36,446,890 and 2016-- 35,856,856 . The number of shares in the treasury for each of the three years in the period ended December 31, 2018 was as follows: 2018 -- 20,033,108 ; 2017 -- 18,692,901 ; and 2016 -- 17,990,620 . L. Common Shares, Redeemable Common Shares and Preferred Shares (continued) Our common and redeemable common shares are not listed or traded on an established public trading market, and market prices are, therefore, not available. Semiannually, an independent stock valuation firm determines the fair market value of our common and redeemable common shares based upon our performance and financial condition. Since 1979, we have provided a ready market for all shareholders through our direct purchase of their common shares, although we are under no obligation to do so (other than repurchases pursuant to the put option under the Davey 401KSOP and ESOP Plan, as described in Note N). During 2018 , purchases of common shares, both redeemable and common, totaled 2,636,943 shares for $51,116 in cash; we also had direct sales to directors and employees of 17,992 shares for $345 , excluding those shares issued through either the exercise of options or the Employee Stock Purchase Plan. We also sold 395,586 shares to our 401(k) plan for $7,647 and issued 198,189 shares to participant accounts to satisfy our liability for the 2017 employer match in the amount of $3,785 . The liability accrued at December 31, 2018 for the 2018 employer match was $4,126 . There were also 348,973 shares purchased during 2018 under the Employee Stock Purchase Plan. Common and Redeemable Shares Outstanding -- The table below reconciles the activity of the common and redeemable shares outstanding: Common Shares Net of Treasury Shares Redeemable Shares Total Shares outstanding, December 31, 2016 17,866,236 7,056,904 24,923,140 Shares purchased (807,718 ) (890,009 ) (1,697,727 ) Shares sold 362,674 300,132 662,806 Stock subscription offering, employee cash purchases 90,645 — 90,645 Options exercised 241,995 — 241,995 Shares outstanding, December 31, 2017 17,753,832 6,467,027 24,220,859 Shares purchased (1,530,528 ) (1,106,415 ) (2,636,943 ) Shares sold 679,197 281,543 960,740 Stock subscription offering, employee cash purchases 129,245 — 129,245 Options exercised 206,751 — 206,751 Shares outstanding, December 31, 2018 17,238,497 5,642,155 22,880,652 On December 31, 2018 , we had 22,880,652 common shares outstanding, employee options exercisable to purchase 889,814 common shares, partially-paid subscription for 690,260 common shares and purchase rights outstanding for 241,236 common shares. Stock Subscription Offering --Beginning May 2012, the Company offered to eligible employees and nonemployee directors the right to subscribe to common shares of the Company at $9.85 per share in accordance with the provisions of The Davey Tree Expert Company 2004 Omnibus Stock Plan and the rules of the Compensation Committee of the Company's Board of Directors (collectively, the "plan"). The offering period ended on August 1, 2012 and resulted in the subscription of 1,275,428 common shares for $12,563 at $9.85 per share. Under the plan, a participant in the offering purchasing common shares for an aggregate purchase price of less than $5 had to pay with cash. All participants (excluding Company directors and officers) purchasing $5 or more of the common shares had an option to finance their purchase through a down-payment of at least 10% of the total purchase price and a seven -year promissory note for the balance due with interest at 2% . Payments on the promissory note can be made either by payroll deductions or annual lump-sum payments of both principal and interest. Common shares purchased under the plan have been pledged as security for the payment of the promissory note and the common shares will not be issued until the promissory note is paid-in-full. Dividends will be paid on all subscribed shares, subject to forfeiture to the extent that payment is not ultimately made for the shares. L. Common Shares, Redeemable Common Shares and Preferred Shares (continued) All participants in the offering purchasing in excess of $5 of common shares were granted a "right" to purchase one additional common share at a price of $9.85 per share for every three common shares purchased under the plan. As a result of the stock subscription, employees were granted rights to purchase 423,600 common shares. Each right may be exercised at the rate of one-seventh per year and will expire seven years after the date that the right was granted. Employees may not exercise a right should they cease to be employed by the Company.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Accumulated other comprehensive income (loss)	Accumulated Other Comprehensive Income (Loss) Comprehensive income (loss) is comprised of net income and other adjustments that relate to foreign currency translation adjustments and defined benefit pension plan adjustments. We do not provide income taxes on currency translation adjustments, as the earnings of our Canadian operations are considered to be indefinitely reinvested. The following summarizes the components of other comprehensive income (loss) accumulated in shareholders’ equity: Foreign Currency Translation Adjustments Defined Benefit Pension Plans Accumulated Other Comprehensive Income (Loss) Balance at January 1, 2016 $ (6,244 ) $ (7,150 ) $ (13,394 ) Unrealized gains (losses) 744 — 744 Amounts reclassified from accumulated other comprehensive income (loss) — 2,844 2,844 Tax effect — (1,137 ) (1,137 ) Unrecognized amounts from defined benefit pension plans — (2,032 ) (2,032 ) Tax effect — 813 813 Net of tax amount 744 488 1,232 Balance at December 31, 2016 $ (5,500 ) $ (6,662 ) $ (12,162 ) Unrealized gains (losses) 2,195 — 2,195 Amounts reclassified from accumulated other comprehensive income (loss) — 4,822 4,822 Tax effect — (1,962 ) (1,962 ) Unrecognized amounts from defined benefit pension plans — (2,169 ) (2,169 ) Tax effect — 883 883 Net of tax amount 2,195 1,574 3,769 Balance at December 31, 2017 $ (3,305 ) $ (5,088 ) $ (8,393 ) Unrealized gains (losses) (2,514 ) — (2,514 ) Amounts reclassified from accumulated other comprehensive income (loss) — 6,291 6,291 Tax effect — (145 ) (145 ) Unrecognized amounts from defined benefit pension plans — (279 ) (279 ) Tax effect — 6 6 Net of tax amount (2,514 ) 5,873 3,359 Balance at December 31, 2018 $ (5,819 ) $ 785 $ (5,034 ) The amounts reclassified from accumulated other comprehensive income (loss) related to defined benefit pension plans for 2018 , 2017 and 2016 are included in net periodic pension expense classified in the statement of operations as general and administrative or other income (expense).

The Davey 401KSOP and Employee

The Davey 401KSOP and Employee Stock Ownership Plan	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
The Davey 401KSOP and Employee Stock Ownership Plan	The Davey 401KSOP and Employee Stock Ownership Plan On March 15, 1979, we consummated a plan, which transferred control of the Company to our employees. As a part of this plan, we initially sold 120,000 common shares (presently, 23,040,000 common shares adjusted for stock splits) to our Employee Stock Ownership Trust (“ESOT”) for $2,700 . The Employee Stock Ownership Plan (“ESOP”), in conjunction with the related ESOT, provided for the grant to certain employees of certain ownership rights in, but not possession of, the common shares held by the trustee of the ESOT. Annual allocations of shares have been made to individual accounts established for the benefit of the participants. Defined Contribution and Savings Plans-- Most employees are eligible to participate in The Davey 401KSOP and ESOP. Effective January 1, 1997, the plan commenced operations and retained the existing ESOP participant accounts and incorporated a deferred savings plan (a "401(k) plan") feature. Participants in the 401(k) plan are allowed to make before-tax contributions, within Internal Revenue Service established limits, through payroll deductions. Effective January 1, 2009, we match, in either cash or our common shares, 100% of the first one percent and 50% of the next three percent of each participant's before-tax contribution, limited to the first four percent of the employee's compensation deferred each year. All nonbargaining domestic employees who attained age 21 and completed one year of service are eligible to participate. In May 2004, we adopted the 401K Match Restoration Plan, a defined contribution plan that supplements the retirement benefits of certain employees that participate in the savings plan feature of The Davey 401KSOP and ESOP Plan, but are limited in contributions because of tax rules and regulations. The Davey 401KSOP and ESOP Plan includes a put option for shares of the Company’s common stock distributed from the plan. Shares are distributed from the Davey 401KSOP and ESOP Plan to former participants of the plan, their beneficiaries, donees or heirs (each, a “participant”). Since our common stock is not currently traded on an established securities market, if the owners of distributed shares desire to sell their shares, the Company is required to purchase the shares at fair value for two 60 -day periods after distribution of the shares from the Davey 401KSOP and ESOP. The fair value of distributed shares subject to the put option totaled $6,288 and $3,843 as of December 31, 2018 and December 31, 2017, respectively. The fair value of the shares held in the Davey 401KSOP and ESOP totaled $112,761 and $119,677 as of December 31, 2018 and December 31, 2017, respectively. Due to the Company’s obligation under the put option, the distributed shares subject to the put option and the shares held in the Davey 401KSOP and ESOP (collectively referred to as 401KSOP and ESOP related shares) are classified as temporary equity in the mezzanine section of the consolidated balance sheets and totaled $119,049 and $123,520 as of December 31, 2018 and December 31, 2017, respectively. Changes in the fair value of the Davey 401KSOP and ESOP Plan related shares are reflected in retained earnings while net share activity associated with the Davey 401KSOP and ESOP Plan related shares are first reflected in additional paid-in capital and then retained earnings if additional paid in-capital is insufficient. Total compensation for these plans, consisting primarily of the employer match, was $4,053 in 2018 , $3,794 in 2017 , and $3,661 in 2016 .

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation Our shareholders approved the 2014 Omnibus Stock Plan (the “2014 Stock Plan”) at our annual meeting of shareholders on May 20, 2014. The 2014 Stock Plan replaced the expired 2004 Omnibus Stock Plan (the “2004 plan”) previously approved by the shareholders in 2004. The 2014 Stock Plan is administered by the Compensation Committee of the Board of Directors and will remain in effect for ten years. All directors of the Company and employees of the Company and its subsidiaries are eligible to participate in the 2014 Stock Plan. The 2014 Stock Plan (similar to the 2004 plan) continues the maintenance of the Employee Stock Purchase Plan, as well as provisions for the grant of stock options and other stock-based incentives. The 2014 Stock Plan provides for the grant of five percent of the number of the Company’s common shares outstanding as of the first day of each fiscal year plus the number of common shares that were available for grant of awards, but not granted, in prior years. In no event, however, may the number of common shares available for the grant of awards in any fiscal year exceed ten percent of the common shares outstanding as of the first day of that fiscal year. Common shares subject to an O. Stock-Based Compensation (continued) award that is forfeited, terminated, or canceled without having been exercised are generally added back to the number of shares available for grant under the 2014 Stock Plan. Stock-based compensation expense under all share-based payment plans—our Employee Stock Purchase Plan, stock option plans, stock-settled stock appreciation rights, and performance-based restricted stock units—included in the results of operations follows: Year Ended December 31, 2018 2017 2016 Compensation expense, all share-based payment plans $ 3,370 $ 4,049 $ 2,811 Income tax benefit 602 1,315 823 Stock-based compensation consisted of the following: Employee Stock Purchase Plan --Under the Employee Stock Purchase Plan, all full-time employees with one year of service are eligible to purchase, through payroll deduction, common shares. Employee purchases under the Employee Stock Purchase Plan are at 85% of the fair market value of the common shares--a 15% discount. Compensation costs are recognized as payroll deductions are made. The 15% discount of total shares purchased under the plan resulted in compensation cost recognized of $998 in 2018 , $888 in 2017 and $727 in 2016 . Stock Options Plan --The stock options outstanding were awarded under a graded vesting schedule, measured at fair value, and have a term of ten years. Compensation costs for stock options are recognized over the requisite service period on the straight-line recognition method. Compensation cost recognized for stock options was $663 in 2018 , $705 in 2017 and $596 in 2016 . Stock-Settled Stock Appreciation Rights --During the year ended December 31, 2018 , the Compensation Committee of the Board of Directors awarded 121,243 Stock-Settled Stock Appreciation Rights (“SSARs”) to certain management employees which vest ratably over five years. A stock-settled stock appreciation right is an award that allows the recipient to receive common stock equal to the appreciation in the fair market value of our common stock between the date the award was granted and the conversion date of the shares vested. The following table summarizes the SSARs as of December 31, 2018 : Stock-Settled Stock Appreciation Rights Number of Rights Weighted- Average Award Date Value Weighted- Average Remaining Contractual Life Unrecognized Compensation Cost Aggregate Intrinsic Value Unvested, January 1, 2018 448,180 $ 3.10 Granted 121,243 3.84 Forfeited — — Vested (188,441 ) 2.93 Unvested, December 31, 2018 380,982 $ 3.42 2.4 years $ 924 $ 7,505 Compensation costs for SSARs are determined using a fair-value method and amortized over the requisite service period. Compensation expense for SSARs totaled $540 in 2018 , $1,035 in 2017 and $591 in 2016 . O. Stock-Based Compensation (continued) Restricted Stock Units --During the year ended December 31, 2018 , the Compensation Committee of the Board of Directors awarded 31,738 performance-based restricted stock units ("PRSUs") to certain management employees and 13,188 restricted stock units ("RSUs") to nonemployee directors. The Compensation Committee made similar awards in prior periods. The awards vest over specified periods. The following table summarizes restricted stock units as of December 31, 2018 : Restricted Stock Units Number of Stock Units Weighted- Average Grant Date Value Weighted- Average Remaining Contractual Life Unrecognized Compensation Cost Aggregate Intrinsic Value Unvested, January 1, 2018 290,666 $ 14.41 Granted 44,926 18.55 Forfeited — — Vested (87,754 ) 12.94 Unvested, December 31, 2018 247,838 $ 15.68 1.9 years $ 1,727 $ 4,882 Employee PRSUs 209,186 $ 15.40 2.2 years $ 1,401 $ 4,121 Nonemployee Director RSUs 38,652 $ 17.17 1.3 years $ 326 $ 761 Compensation cost for awards is determined using a fair-value method, amortized over the requisite service period. “Intrinsic value” is defined as the amount by which the fair market value of a common share of stock exceeds the exercise price of a performance-based restricted stock unit. Compensation expense on restricted stock unit awards totaled $1,169 in 2018 , $1,421 in 2017 and $897 in 2016 . The fair value of each award was estimated on the date of grant using a binomial option-pricing model. The binomial model considers a range of assumptions related to volatility, risk-free interest rate and employee exercise behavior. Expected volatilities utilized in the binomial model are based on historical volatility of our share prices and other factors. Similarly, the dividend yield is based on historical experience and expected future changes. The binomial model also incorporates exercise and forfeiture assumptions based on an analysis of historical data. The expected life of the stock-based awards is derived from the output of the binomial model and represents the period of time that awards granted are expected to be outstanding. The fair values of stock-based awards granted were estimated at the dates of grant with the following weighted-average assumptions: Year Ended December 31, 2018 2017 2016 Volatility rate 10.1 % 10.3 % 10.6 % Risk-free interest rate 2.7 % 2.2 % 1.8 % Expected dividend yield .7 % .7 % .7 % Expected life of awards (years) 9.2 8.9 9.5 O. Stock-Based Compensation (continued) General Stock Option Information --The following table summarizes activity under the stock option plans for the year ended December 31, 2018 : Stock Options Number of Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life Unrecognized Compensation Cost Aggregate Intrinsic Value Outstanding, January 1, 2018 1,528,615 $ 13.05 Granted 143,250 19.10 Exercised (147,321 ) 9.93 Forfeited (58,280 ) 13.29 Outstanding, December 31, 2018 1,466,264 $ 13.94 5.9 years $ 1,393 $ 8,446 Exercisable, December 31, 2018 889,814 $ 11.79 4.7 years $ 7,037 “Intrinsic value” is defined as the amount by which the market price of a common share of stock exceeds the exercise price of an option. Information regarding the stock options outstanding at December 31, 2018 is summarized below: Stock Options Exercise Price Number Outstanding Weighted-Average Remaining Contractual Life Weighted- Average Exercise Price Number Exercisable Weighted- Average Exercise Price Employee options: $ 8.00 88,413 0.8 years $ 8.00 88,413 $ 8.00 8.30 107,000 1.8 years 8.30 107,000 8.30 11.60 270,414 4.5 years 11.60 270,414 11.60 13.20 284,822 5.5 years 13.20 211,422 13.20 15.05 219,965 6.5 years 15.05 112,765 15.05 16.35 230,800 7.5 years 16.35 77,800 16.35 17.60 129,300 8.5 years 17.60 22,000 17.60 19.10 135,550 9.5 years 19.10 — 19.10 1,466,264 5.9 years $ 13.94 889,814 $ 11.79 We issue common shares from treasury upon the exercise of stock options, stock-settled stock appreciation rights, performance-based restricted stock units or purchases under the Employee Stock Purchase Plan. Tax Benefits of Stock-Based Compensation-- Our total income tax benefit from share-based awards--as recognized in our consolidated statement of operations--for the last three years was: $602 in 2018 , $1,315 in 2017 , and $823 in 2016 . Tax benefits for share-based awards are accrued as stock compensation expense and recognized in our consolidated statement of operations. Tax benefits on share-based awards are realized when: (a) stock-settled stock appreciation rights are exercised; (b) performance-based restricted stock units vest; and (c) stock options are exercised. When actual tax benefits realized exceed the tax benefits accrued for share-based awards, we realize an excess tax benefit. We had excess tax benefits of: $453 in 2018 , $691 in 2017 , and $1,113 in 2016 .

Defined Benefit Pension Plans

Defined Benefit Pension Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Defined Benefit Pension Plans	Defined Benefit Pension Plans We have defined benefit pension plans covering certain current and retired U.S. employees. Plans include: (i) the Employee Retirement Plan (“ERP”) for employees hired prior to January 1, 2009; (ii) a Supplemental Executive Retirement Plan (“SERP”) for which future benefit accruals were frozen effective at the end of the second quarter 2015; and (iii) a Benefit Restoration Pension Plan (“Restoration Plan”) for certain key employees hired prior to January 1, 2009. Both the SERP and the Restoration Plan are defined benefit plans under which nonqualified supplemental pension benefits will be paid in addition to amounts paid under our qualified retirement defined benefit pension plans, which are subject to Internal Revenue Service limitations on covered compensation. Effective December 31, 2008, enhanced benefits were implemented to our defined contribution savings plan--The Davey 401KSOP and ESOP--at which time, the Board of Directors approved an amendment to freeze the ERP and the Restoration Plan. The ERP was closed to new participants after December 2008. In connection with the freeze of the ERP, the Restoration Plan and the SERP, (a) benefits currently being paid to retirees continue and (b) benefits accrued through December 31, 2008 for employees covered by the ERP were not affected. All ERP, Restoration Plan and SERP balances remain intact and participant account balances, as well as service credits for vesting and retirement eligibility, remain intact and continue in accordance with the terms of the plans. Only future accruals were eliminated with: (i) the 2008 freeze of the ERP and Restoration Plan and (ii) the 2015 freeze of the SERP. The change in benefit obligations and the fair value of plans assets follows: December 31, 2018 2017 Change in benefit obligation Projected benefit obligation at beginning of year $ 19,403 $ 24,833 Service cost 400 530 Interest cost 718 1,002 Actuarial (gains)/losses (77 ) 1,865 Amendments — — Settlements (13,118 ) (8,400 ) Benefits paid (262 ) (427 ) Projected benefit obligation at end of year $ 7,064 $ 19,403 Accumulated benefit obligation at end of year $ 7,064 $ 19,403 December 31, 2018 2017 Change in fair value of plan assets Fair value of plan assets at beginning of year $ 7,105 $ 11,509 Actual return on plan assets 239 845 Plan expenses, including PBGC premiums (364 ) (513 ) Employer contributions 10,158 4,091 Settlements (13,118 ) (8,400 ) Benefits paid (262 ) (427 ) Fair value of plan assets at end of year $ 3,758 $ 7,105 The settlements in the change in benefit obligation and in the change in fair value of plan assets arise from: (i) lump sum offering to 905 participants in our ERP plan during the fourth quarter 2018 as part of our plan termination process; and (ii) a purchase of a guaranteed group annuity contract during the fourth quarter 2017 from a third-party insurance company which P. Defined Benefit Pension Plans (continued) unconditionally and irrevocably guarantees the full payment of all annuity payments to a combination of participants currently receiving benefits or entitled to future benefits from the ERP plan. December 31, 2018 2017 Funded status of the plans Fair value of plan assets $ 3,758 $ 7,105 Projected benefit obligation 7,064 19,403 Funded status of the plans $ (3,306 ) $ (12,298 ) December 31, 2018 2017 Funded status by plan ERP $ (332 ) $ (9,084 ) SERP (2,564 ) (2,759 ) Restoration Plan (410 ) (455 ) $ (3,306 ) $ (12,298 ) December 31, 2018 2017 Amounts reported in the consolidated balance sheets Current liability $ (187 ) $ (175 ) Noncurrent liability (3,119 ) (12,123 ) Funded status of the plans $ (3,306 ) $ (12,298 ) Amounts included in accumulated other comprehensive income (loss), related to our defined benefit pension plans follow: At December 31, 2018 At December 31, 2017 Pretax Net of Tax Pretax Net of Tax Amounts reported in accumulated other comprehensive income Unrecognized net actuarial loss $ 2,139 $ (714 ) $ 8,086 $ 4,919 Unrecognized prior service cost 214 (71 ) 278 169 $ 2,353 $ (785 ) $ 8,364 $ 5,088 To the extent actuarial losses exceed the greater of 10% of the projected benefit obligation or market-related value of plan assets, the unrecognized actuarial losses will be amortized straight-line on a plan-by-plan basis, over the remaining expected future working lifetime of active participants, except for the SERP, which, after the plan freeze, is being amortized based on the remaining life expectancy of plan participants. The total amount of unrecognized prior service cost was amortized straight-line on a plan-by-plan basis. P. Defined Benefit Pension Plans (continued) The total amortization associated with these amounts that is expected to be recognized in net periodic benefit expense for 2019 follows: Year ending December 31, 2019 Pretax Net of Tax Amortization of Costs Expected to be Recognized Next Year Unrecognized net actuarial loss $ 175 $ 131 Unrecognized prior service cost 64 48 $ 239 $ 179 The aggregate projected benefit obligation, accumulated benefit obligation and fair value of plan assets for plans in which the fair value of plan assets is less than either the projected benefit obligation or accumulated benefit obligation follow: December 31, 2018 2017 For pension plans with accumulated benefit obligations in excess of plan assets Projected benefit obligation $ 7,064 $ 19,403 Accumulated benefit obligation 7,064 19,403 Fair value of plan assets 3,758 7,105 The actuarial assumptions follow. The discount rates were used to measure the year-end benefit obligation and compute pension expense for the subsequent year. December 31, 2018 2017 2016 Actuarial assumptions Discount rate 4.35 % 3.70 % 4.20 % Expected long-term rate of return on plan assets 2.50 2.50 5.00 Net periodic benefit expense (income) associated with the defined benefit pension plans included the following components: Year Ended December 31, 2018 2017 2016 Components of pension expense (income) Service costs--increase in benefit obligation earned $ 400 $ 530 $ 370 Interest cost on projected benefit obligation 718 1,002 1,243 Expected return on plan assets (231 ) (638 ) (1,044 ) Curtailment loss — — — Settlement loss 5,499 3,849 2,346 Amortization of net actuarial loss 728 909 951 Amortization of prior service cost 64 64 — Net pension expense of defined benefit pension plans $ 7,178 $ 5,716 $ 3,866 P. Defined Benefit Pension Plans (continued) Investment Strategy and Risk Management for Plan Assets-- Our investment strategy is to manage the plan assets in order to pay retirement benefits to plan participants while minimizing our cash contributions over the life of the plans. This is accomplished by maintaining liquidity and preserving principal through diversification in high-quality investments through the use of investment managers and mutual funds. Performance of all investment managers and mutual funds is monitored quarterly and evaluated over rolling three -to- five year periods. In December 2017, we revised our investment policy to reallocate 100% of our plan assets into the fixed income and cash asset class from the prior target allocations of: (a) equities of a minimum 20% to a maximum of 40% ; (b) fixed income and cash of a minimum 50% to a maximum of 70% ; and, (c) alternative investments of a minimum of zero to a maximum of 15% . The purpose of the fixed income asset class is to provide a deflation hedge, to reduce the overall volatility of plan assets and to produce current income in support of the needs of the plan. Fixed income assets can be invested in U.S. government and prime money market funds, U.S. Treasuries, insured certificates of deposit and U.S. investment grade corporates of at least "A" or better quality and other high-quality debt securities. Other than investments in U.S. government or government agencies, no single debt issue will be allowed to exceed 5% market value of the debt portfolio. Short-selling, securities lending, financial futures, margins, options, and derivatives are not used. Investments in nonmarketable securities, commodities, or direct ownership of real estate are prohibited. Rate-of-return-on-assets assumptions are made based on the mix of assets according to our investment policy. Given the reallocation of plan assets into the fixed income and cash asset class, the overall expected long-term rate-of-return-on-plan assets net of investment manager fees as at December 31, 2018 , was 2.50% . Plan Assets --The fair values of our pension plan assets at December 31, 2018 by asset category, using the three-level hierarchy of fair value inputs, were as follows: Fair Value Measurements at December 31, 2018 Using: Description Total Carrying Value at December 31, 2018 Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Asset Category Money market funds $ 3,758 $ 3,758 $ — U.S. large-cap equities Growth — — — Value — — — U.S. small/mid-cap equities Growth — — — Value — — — International equities Growth — — — Value — — — Fixed income — — — Multiclass world-allocation mutual funds — — — $ 3,758 $ — $ 3,758 $ — P. Defined Benefit Pension Plans (continued) The fair values of our pension plan assets at December 31, 2017 by asset category, using the three-level hierarchy of fair value inputs, were as follows: Fair Value Measurements at December 31, 2017 Using: Description Total Carrying Value at December 31, 2017 Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Asset Category Money market funds $ 897 $ — $ 897 $ — U.S. large-cap equities Growth 576 576 — — Value 542 542 — — U.S. small/mid-cap equities Growth 246 246 — — Value 247 247 — — International equities Growth 376 376 — — Value 366 366 — — Fixed income 3,070 3,070 — — Multiclass world-allocation mutual funds 785 785 — — $ 7,105 $ 6,208 $ 897 $ — Within the pension plan asset categories, the Level 1 investments are publicly traded in active markets and are valued using the net asset value or closing price of the investment at the measurement date. Securities held by a money market fund are generally high quality and liquid; however, they are reflected as Level 2 because the inputs used to determine fair value are not quoted prices in an active market. Expected Benefit Plan Contributions --It is our practice to make contributions to comply with the minimum funding requirements of ERISA. In accordance with such practice, contributions totaling $191 are required for 2019; however, we may make additional discretionary contributions. Expected Benefit Plan Payments --The benefits, as of December 31, 2018 , expected to be paid to defined-benefit plan participants in each of the next five years, and in the aggregate for the five years thereafter, follows: Participants Benefits Estimated future payments Year ending December 31, 2019 $ 356 2020 379 2021 384 2022 386 2023 389 Years 2024 to 2028 1,986 Multiemployer Defined Benefit Pension Plans --In providing services to our utility services customers, we contribute to multiemployer defined benefit pension plans under the terms of collective-bargaining agreements that cover certain of our union-represented employees. P. Defined Benefit Pension Plans (continued) These plans generally provide retirement benefits to participants based on their service to contributing employers. We do not administer these multiemployer plans. In general, these plans are managed by a board of trustees with the unions appointing certain trustees and other contributing employers of the plan appointing certain members. We generally are not represented on the board of trustees. The risks of participating in these multiemployer plans are different from single-employer plans in that: (a) assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers; (b) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be assumed by the remaining participating employers; and, (c) if we choose to stop participating in a multiemployer plan, we may be required to pay the plan an amount based on the underfunded status of the plan, referred to as a withdrawal liability. Our participation in the multiemployer defined benefit pension plans is summarized in the table below. The “EIN/Pension Plan Number” column provides the Employer Identification Number (“EIN”) and the three-digit plan number. The most recent Pension Protection Act of 2006 (the “PPA”) zone status is from the Form 5500, “Annual Return/Report of Employee Benefit Plan,” filed by the plan and certified by the plan's actuary. The PPA zone status describes plans that are underfunded. Among other factors, plans in the “critical” red zone are generally less than 65% funded; plans in the “endangered” yellow zone are less than 80% funded; and, plans in the “safe” green zone are at least 80% funded. Pension Fund EIN/Pension Plan Number Pension Protection Act Zone Status FIP/RP Status Pending Implemented Davey Tree Contributions Surcharge Imposed Expiration Dates of Bargaining Agreement 2018 2017 2018 2017 2016 National Electric Benefit Fund 53-0181657/001 Green Green No $ 768 $ 785 $ 712 No Ranging from December 31, 2018 to December 31, 2022 Eighth District Electrical Pension Fund 84-6100393/001 Green Green No 142 102 90 No December 26, 2020 $ 910 $ 887 $ 802 We were not listed in the Form 5500 for either plan as having provided more than 5% of the total contributions. Both the National Electric Benefit Fund and the Eighth District Electrical Pension Fund are green zone status--safe--which represents at least 80% funded and does not require a “financial improvement plan” (“FIP”) or a “rehabilitation plan” (“RP”). We are party to ten collective-bargaining agreements with the National Electric Benefit Fund, with expiration dates ranging from December 31, 2018 to December 31, 2022, and one collective-bargaining agreement with Eighth District Electrical Pension Fund which expires on December 26, 2020. Expired agreements are currently being renegotiated.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On December 22, 2017, the President of the United States (“U.S.”) signed into law the Tax Cuts and Jobs Act (the "Tax Reform Act"), which enacted significant changes to U.S. tax laws. Some of the provisions of the new tax law affecting corporations include, but are not limited to lowering the U.S. corporate income tax rate from 35% to 21% effective January 1, 2018, immediate expensing of certain qualified capital expenditures, implementing a territorial tax system and imposing a one-time transitional toll tax on deferred foreign earnings. In the fourth quarter 2017, the Company recorded the provisional tax effects, including a tax charge of $1,000 due to the remeasurement of deferred tax assets and liabilities and an estimated tax liability of $6,100 due to the transition toll tax on the deemed repatriation of deferred foreign earnings of non-U.S. operations. The Tax Reform Act was the main reason for the reduction of our effective tax rate for the year ended December 31, 2018. On December 22, 2017, the Securities and Exchange Commission (“SEC”) issued Staff Accounting Bulletin 118 (“SAB 118”). This guidance allowed registrants a “measurement period”, not to exceed one year from the date of enactment, to complete their accounting for the tax effects of the Tax Reform Act. SAB 118 further directed that during the measurement Q. Income Taxes (continued) period, registrants who were able to make reasonable estimates for the tax effects of the Tax Reform Act should include those amounts in their financial statements as “provisional” amounts. Registrants were to reflect adjustments over subsequent periods as they were able to refine their estimates and complete their accounting for the tax effects of the Tax Reform Act. The provisional amounts computed by the Company were finalized when the U.S. corporate income tax return for 2017 was filed in September 2018. The change for the provisional amount to the final amount was immaterial. Other provisions of the Tax Reform Act include a new minimum tax on certain foreign earnings (the Global Intangibles Low-taxed Income, or “GILTI”), a new tax on certain payments to foreign related parties (the Base Erosion Anti-Avoidance tax, or “BEAT”), a new incentive for Foreign-derived Intangibles Income (“FDII”), repealing the deduction for domestic production activities, changes to the limitation on the deductibility of certain executive compensation, and new limitations on the deductibility of interest expense. Generally, the tax effect of these other provisions began for the Company in the year ended December 31, 2018 with no material effect. Income before income taxes was attributable to the following sources: Year Ended December 31, 2018 2017 2016 United States $ 37,377 $ 38,800 $ 35,867 Canada 119 (806 ) 1,377 Total $ 37,496 $ 37,994 $ 37,244 The provision for income taxes follows: Year Ended December 31, 2018 2017 2016 Currently payable: Federal $ 3,165 $ 9,914 $ 12,216 State 2,290 2,469 2,286 Canadian 50 (262 ) 398 Total current 5,505 12,121 14,900 Deferred taxes 4,014 3,753 60 Total taxes on income $ 9,519 $ 15,874 $ 14,960 A reconciliation of the expected statutory U.S. federal rate to our actual effective income tax rate follows: Year Ended December 31, 2018 2017 2016 Statutory U.S. federal tax rate 21.0 % 35.0 % 35.0 % State income taxes, net of federal benefit 5.7 4.9 4.0 Effect of Canadian income taxes .1 .3 (.2 ) Nondeductible expenses 2.1 2.2 2.2 ESOP dividend deduction (.3 ) (.6 ) (.7 ) Uncertain tax adjustments and audit settlement (3.8 ) (.2 ) .2 Income tax reform - deferred rate remeasurement — 2.5 — All other, net .6 (2.3 ) (.3 ) Effective income tax rate 25.4 % 41.8 % 40.2 % Q. Income Taxes (continued) Deferred income taxes reflect the tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. A valuation allowance is recorded when it is more-likely-than-not that an income tax benefit will not be realized. Significant components of our noncurrent net deferred tax assets and liabilities at December 31, were as follows: December 31, 2018 2017 Deferred tax assets: Self-insurance accruals $ 17,579 $ 14,186 Accrued compensated absences 1,565 1,747 Accrued expenses and other liabilities 742 798 Accrued stock compensation 1,772 1,571 Defined benefit pension plans 442 2,289 Foreign tax credit carryforward 2,117 605 Other future deductible amounts, net 3,271 3,661 27,488 24,857 Less deferred tax asset valuation allowance 1,683 — 25,805 24,857 Deferred tax liabilities: Intangibles 1,178 969 Prepaid expenses 3,160 2,300 Property and equipment 20,894 16,773 25,232 20,042 Net deferred tax assets--noncurrent $ 573 $ 4,815 We treat all of our Canadian subsidiary earnings through December 31, 2018 as permanently reinvested and have not provided any U.S. federal or state tax thereon. As of December 31, 2018 , approximately $28,856 of undistributed earnings attributable to our Canadian operations was considered to be indefinitely invested. Presently, our intention is to reinvest the earnings permanently. If, in the future, these earnings are distributed to the U.S. in the form of dividends or otherwise, or if the Company determines such earnings will be remitted in the foreseeable future, the Company would be subject to Canadian withholding taxes. It is not practicable to estimate the amount of taxes that would be payable upon remittance of these earnings given the various tax planning alternatives that we could employ should we decide to repatriate those earnings. As of December 31, 2018, we recorded a valuation allowance on foreign tax credit carryforwards that arose due to the transition toll tax on the deemed repatriation of deferred foreign earnings of non-U.S. operations due to the Tax Reform Act and the remaining carryforward credits that were generated in 2010. Management presently believes that it is more-likely-than-not that the deferred tax asset, related to the foreign tax credits that expire in 2020 and 2027, will not be fully realized. The criteria considered in making the determination included the ability to utilize tax-planning strategies, historical and projected operating results, and the period of time over which the foreign tax credit can be utilized. The amount of income taxes that we pay is subject to audit by U.S. federal, state, local and Canadian tax authorities, which may result in proposed assessments. Our estimate for the potential outcome for any uncertain tax issue is highly judgmental. Uncertain tax positions are recognized only if they are more-likely-than-not to be upheld during examination based on their technical merits. The measurement of the uncertain tax position is based on the largest benefit amount that is more-likely-than-not (determined on a cumulative probability basis) to be realized upon settlement of the matter. If payment of these Q. Income Taxes (continued) amounts ultimately proves to be unnecessary, the reversal of the liabilities would result in tax benefits being recognized in the period when we determine the liabilities are no longer necessary. If the estimate of tax liabilities proves to be less than the ultimate settlement, a further charge to expense may result. The balance of unrecognized benefits and the amount of related interest and penalties at December 31, were as follows: December 31, 2018 2017 Unrecognized tax benefits $ 1,325 $ 2,581 Portion, if recognized, would reduce tax expense and effective tax rate 599 1,948 Accrued interest on unrecognized tax benefits 35 128 We recognize interest accrued related to unrecognized tax benefits in income tax expense. Penalties, if incurred, would be recognized as a component of income tax expense. The Company is routinely under audit by U.S. federal, state, local and Canadian authorities in the area of income tax. These audits include questioning the timing and the amount of income and deductions and the allocation of income and deductions among various tax jurisdictions. During 2018, we decreased our unrecognized tax benefits by $1,500 as a result of the proposed settlement of the IRS audits of our 2015 and 2016 U.S. income tax returns. The audit was closed in the third quarter 2018. With the exception of U.S. state jurisdictions and Canada, the Company is no longer subject to examination by tax authorities for the years through 2016. As of December 31, 2018 , we believe it is reasonably possible that the total amount of unrecognized tax benefits will not significantly increase or decrease. The changes in our unrecognized tax benefits are summarized in the table below: Year Ended December 31, 2018 2017 2016 Balance, beginning of year $ 2,581 $ 2,532 $ 2,557 Additions based on tax positions related to the current year 224 650 402 Additions for tax positions of prior years 20 (21 ) 51 Reductions for tax positions of prior years (1,500 ) — (39 ) Lapses in statutes of limitations — (580 ) (439 ) Balance, end of year $ 1,325 $ 2,581 $ 2,532

Earnings Per Share Information

Earnings Per Share Information	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share Information	Earnings Per Share Information Earnings per share is computed as follows (prior periods have been adjusted for the two-for-one stock split of our common shares effective June 1, 2017): Year Ended December 31, 2018 2017 2016 Income available to common shareholders: Net income $ 27,977 $ 22,120 $ 22,284 Weighted-average shares: Basic: Outstanding 23,698,478 24,793,086 25,378,600 Partially-paid share subscriptions 690,260 764,382 833,440 Basic weighted-average shares 24,388,738 25,557,468 26,212,040 Diluted: Basic from above 24,388,738 25,557,468 26,212,040 Incremental shares from assumed: Exercise of stock subscription purchase rights 141,287 146,453 142,746 Exercise of stock options and awards 950,593 993,141 892,568 Diluted weighted-average shares 25,480,618 26,697,062 27,247,354 Share data: Earnings per share--basic $ 1.15 $ .87 $ .85 Earnings per share--diluted $ 1.10 $ .83 $ .82

Operations by Business Segment

Operations by Business Segment and Geographic Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Operations by Business Segment and Geographic Information	Operations by Business Segment and Geographic Information We provide a wide range of arboricultural, horticultural, environmental and consulting services to residential, utility, commercial and government entities throughout the United States and Canada. We have two reportable operating segments organized by type or class of customer: Residential and Commercial, and Utility. Residential and Commercial --Residential and Commercial provides services to our residential and commercial customers including: the treatment, preservation, maintenance, removal and planting of trees, shrubs and other plant life; the practice of landscaping, grounds maintenance, tree surgery, tree feeding and tree spraying; the application of fertilizer, herbicides and insecticides; and, natural resource management and consulting, forestry research and development, and environmental planning. Utility --Utility is principally engaged in providing services to our utility customers--investor-owned, municipal utilities, and rural electric cooperatives--including: the practice of line-clearing and vegetation management around power lines, rights-of-way and chemical brush control; and, natural resource management and consulting, forestry research and development and environmental planning. All other operating activities, including research, technical support and laboratory diagnostic facilities, are included in “All Other.” Measurement of Segment Profit and Loss and Segment Assets --We evaluate performance and allocate resources based primarily on operating income and also actively manage business unit operating assets. The accounting policies of the reportable segments are the same as those described in the summary of significant accounting policies except that (a) we compute and recognize depreciation expense for our segments only by the straight-line method and (b) state income taxes are allocated to the segments. Corporate expenses are substantially allocated among the operating segments, but the nature of expenses allocated may differ from year-to-year. There are no intersegment revenues. S. Operations by Business Segment and Geographic Information (continued) Segment assets are those generated or directly used by each segment, and include accounts receivable, operating supplies, and property and equipment. Information on reportable segments and reconciliation to the consolidated financial statements follows: Utility Services Residential Commercial Services All Other Reconciling Adjustments Consolidated Fiscal Year 2018 Revenues $ 537,484 $ 486,005 $ 1,302 $ — $ 1,024,791 Income (loss) from operations 32,370 47,812 (19,816 ) (4,676 ) (a) 55,690 Interest expense (7,039 ) (7,039 ) Interest income 350 350 Other income (expense), net (11,505 ) (11,505 ) Income before income taxes $ 37,496 Depreciation $ 29,526 $ 21,720 $ — $ 3,668 (b) $ 54,914 Amortization 211 1,842 — 2 2,055 Capital expenditures 32,148 22,256 — 6,006 60,410 Segment assets, total 239,426 208,369 — 78,828 (c) 526,623 Fiscal Year 2017 Revenues $ 466,727 $ 446,028 $ 3,203 $ — $ 915,958 Income (loss) from operations 18,223 41,158 (2,634 ) (4,556 ) (a) 52,191 Interest expense (4,886 ) (4,886 ) Interest income 292 292 Other income (expense), net (9,603 ) (9,603 ) Income before income taxes $ 37,994 Depreciation $ 27,928 $ 19,384 $ — $ 3,390 (b) $ 50,702 Amortization 122 2,240 — 22 2,384 Capital expenditures 26,910 23,199 — 6,991 57,100 Segment assets, total 189,662 197,698 — 85,775 (c) 473,135 Fiscal Year 2016 Revenues $ 433,379 $ 410,878 $ 1,421 $ — $ 845,678 Income (loss) from operations 19,256 36,640 (4,318 ) (2,711 ) (a) 48,867 Interest expense (4,393 ) (4,393 ) Interest income 255 255 Other income (expense), net (7,485 ) (7,485 ) Income before income taxes $ 37,244 Depreciation $ 26,855 $ 17,198 $ — $ 3,231 (b) $ 47,284 Amortization 135 2,136 — 35 2,306 Capital expenditures 28,660 21,819 — 6,167 56,646 Segment assets, total 171,220 166,858 — 85,861 (c) 423,939 S. Operations by Business Segment and Geographic Information (continued) Reconciling adjustments from segment reporting to consolidated external financial reporting include unallocated corporate items: (a) Reconciling adjustments from segment reporting to consolidated external financial reporting include reclassification of depreciation expense and allocation of corporate expenses. (b) Adjustments to declining-balance method depreciation expense from straight-line method and depreciation and amortization of corporate assets. (c) Corporate assets include cash, prepaid expenses, corporate facilities, enterprise-wide information systems and other nonoperating assets. Geographic Information -- The following presents revenues and long-lived assets by geographic territory: Year Ended December 31, 2018 2017 2016 Revenues United States $ 949,317 $ 847,540 $ 775,870 Canada 75,474 68,418 69,808 $ 1,024,791 $ 915,958 $ 845,678 December 31, 2018 2017 2016 Long-lived assets, net United States $ 251,181 $ 242,118 $ 224,727 Canada 20,374 21,893 20,439 $ 271,555 $ 264,011 $ 245,166

Revenue Recognition (Notes)

Revenue Recognition (Notes)	12 Months Ended
	Dec. 31, 2018
Revenue Recognition [Abstract]
Revenue from contracts with customers [Text Block]	Revenue Recognition We account for revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers, which we adopted on January 1, 2018, using the modified retrospective method. See Note C for further discussion of the adoption, including the impact on our 2018 financial statements. Nature of Performance Obligations and Significant Judgments At contract inception, the Company assesses the goods and services promised in its contracts with customers and identifies a performance obligation for each promised good or service (or bundle of goods and services) that is distinct. To identify the performance obligations, the Company considers all of the goods or services promised in the contract regardless of whether they are explicitly stated or are implied by customary business practices. A description of our performance obligations is included below. • Residential and Commercial Services - We provide a wide array of services for our residential and commercial customers including the treatment, preservation, maintenance, removal and planting of trees, shrubs and other plant life, landscaping, grounds maintenance, the application of fertilizer, herbicides and insecticides, natural resource management and consulting, forestry research and development, and environmental planning. A contract with a customer may include only one of these services, all of these services, or a combination of these services. For contracts in which we provide all, or a combination of, these services, we believe that the nature of our promise is to provide an integrated property management service for our customer. In these contracts, the customer has effectively outsourced the care and maintenance of its property grounds to us during the duration of the contract as we are responsible for providing a continuous delivery of outsourced maintenance activities over the contract term. As such, T. Revenue Recognition (continued) for contracts that contain a combination of services, we have concluded that we have a single performance obligation, which is accounted for as a series of distinct services. • Utility Services - We provide a suite of vegetation management or arboricultural services to our utility customers (investor-owned, municipal utilities, and rural electric cooperatives) including the practice of line-clearing and vegetation management around power lines and rights-of-way, chemical brush control, natural resource management and consulting, forestry research and development, and environmental planning. A contract with a customer may include only one of these services, all of these services, or a combination of these services. For contracts in which we provide all, or a combination of, these services, we believe that the nature of our promise is to provide an integrated overall vegetation management service, rather than the performance of discrete activities or services for the customer. As such, for contracts that contain a combination of services, we have concluded that we have a single performance obligation, which is accounted for as a series of distinct services. Our contracts with our customers generally originate upon the completion of a quote for services for residential and commercial customers or the receipt of a purchase order (or similar work order) for utility customers. In some cases, our contracts are governed by master services agreements, in which case our contract under ASC 606 consists of the combination of the master services agreement and the quote/purchase order. Many of our contracts have a stated duration of one year or less or contain termination clauses that allow the customer to cancel the contract after a specified notice period, which is typically less than 90 days. Due to the fact that many of our arrangements allow the customer to terminate for convenience, the duration of the contract for revenue recognition purposes generally does not extend beyond the services that we have actually transferred. As a result, many of our contracts are, in effect, day-to-day or month-to-month contracts. Revenue from our residential, commercial, and utility performance obligations is recognized over time as the customer simultaneously receives and consumes the benefits of our services as we perform them. Many of our contracts compensate us based on an agreed upon price for each increment of service provided to the customer. Therefore, revenue is mainly recognized as each increment of service is provided to the customer at the amount that we are contractually entitled to. For contracts that contain a fixed price, we generally use a units-delivered based output method to measure progress. Revenue from our consulting services is also recognized over time and we use a cost-based input method to measure progress. Payment for our services is generally due within 30 days of such services being provided to the customer. The transaction price for our contracts is determined upon establishment of the contract that contains the final terms of the sale, including the description, quantity, and price of each service purchased. Certain of our contracts contain variable consideration, including index-based pricing, chargebacks, and prompt payment discounts. The Company estimates variable consideration and performs a constraint analysis for these contracts on the basis of both historical information and current trends. However, these types of variable consideration do not have a material effect on the Company’s revenue, either individually or in the aggregate. In addition, although our contracts generally include fixed pricing for each increment of service, the ultimate quantity of services that will be required in order to fulfill our performance obligations is unknown at contract inception. Therefore, our total transaction price ultimately varies based on the quantity and types of services provided to our customer. However, this type of variable consideration is allocated entirely to the distinct services within the series to which it relates. T. Revenue Recognition (continued) Disaggregation of Revenue The following tables disaggregate our revenue for the year ended December 31, 2018 by major sources: Year Ended December 31, 2018 Utility Residential and Commercial All Other Consolidated Type of service: Tree and plant care $ 394,481 $ 290,940 $ (1,520 ) $ 683,901 Grounds maintenance — 117,498 — 117,498 Storm damage services 13,864 9,447 — 23,311 Consulting and other 129,139 68,120 2,822 200,081 Total revenues $ 537,484 $ 486,005 $ 1,302 $ 1,024,791 Geography: United States $ 499,242 $ 448,773 $ 1,302 $ 949,317 Canada 38,242 37,232 — 75,474 Total revenues $ 537,484 $ 486,005 $ 1,302 $ 1,024,791 Contract Balances Our contract liabilities consist of advance payments, billings in excess of costs incurred and deferred revenue. The Company has recognized $1,443 of revenue for the twelve months ended months ended December 31, 2018 that was included in the contract liability balance at December 31, 2017 . Net contract liabilities consisted of the following: December 31, December 31, Contract liabilities - current $ 2,907 $ 2,072 Contract liabilities - noncurrent 2,287 2,020 Net contract liabilities $ 5,194 $ 4,092 Practical Expedients & Accounting Policy Elections • Remaining performance obligations - The Company’s contracts for service revenue have an original duration of one year or less. Therefore, because of the short duration of these contracts, the Company has not disclosed the transaction price for the future performance obligations as of the end of each reporting period or when the Company expects to recognize this revenue. • Incremental costs of obtaining a contract - The Company’s contracts for service revenue have an original duration of one year or less. Therefore, the Company has elected to expense these costs as incurred. • Right to invoice - For the Company’s contracts in which it has the right to invoice the customer on the basis of actual work performed (i.e., output), the Company has elected to measure the satisfaction of performance obligation(s) on the basis of actual work performed, as the invoiced amount directly corresponds to the value transferred to the customer. • Sales taxes - The Company has, as an accounting policy election, decided to exclude from the measurement of the transaction price all sales taxes assessed by a governmental authority. • Significant financing component - The Company’s contracts do not allow for payment terms which exceed one year, and thus need not account for the effects of a significant financing component.

Fair Value Measurements and Fin

Fair Value Measurements and Financial Instruments	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value measurements and financial instruments	Fair Value Measurements and Financial Instruments Financial Accounting Standards Board Accounting Standard Codification 820, “Fair Value of Measurements and Disclosures (“Topic 820”)” defines fair value based on the price that would be received to sell an asset or the exit price that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. Market participants are defined as buyers or sellers in the principal or most advantageous market for the asset or liability that are independent of the reporting entity, knowledgeable and able and willing to transact for the asset or liability. Valuation Hierarchy --Topic 820 establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value. The hierarchy prioritizes the inputs into three broad levels: Level 1 inputs are quoted prices in active markets for identical assets or liabilities that the entity has the ability to access. Level 2 inputs are observable inputs other than prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated with observable market data. Level 3 inputs are unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. Our assets and liabilities measured at fair value on a recurring basis at December 31, 2018 and December 31, 2017 , were as follows: Fair Value Measurements at December 31, 2018 Using: Total Carrying Value at Quoted prices in active markets Significant other observable inputs Significant unobservable inputs Description December 31, 2018 (Level 1) (Level 2) (Level 3) Assets: Assets invested for self-insurance, classified as other assets, noncurrent $ 15,379 $ 15,379 $ — $ — Defined benefit pension plan assets 3,758 — 3,758 — Liabilities: Deferred compensation $ 2,459 $ — $ 2,459 $ — U. Fair Value Measurements and Financial Instruments (continued) Fair Value Measurements at December 31, 2017 Using: Total Carrying Value at Quoted prices in active markets Significant other observable inputs Significant unobservable inputs Description December 31, 2017 (Level 1) (Level 2) (Level 3) Assets: Assets invested for self-insurance, classified as other assets, noncurrent $ 19,422 $ 19,422 $ — $ — Defined benefit pension plan assets 7,105 6,208 897 — Liabilities: Deferred compensation $ 2,146 $ — $ 2,146 $ — The estimated fair value of the deferred compensation--classified as Level 2--is based on the value of the Company's common shares, determined by independent valuation. Fair Value of Financial Instruments --The fair values of our current financial assets and current liabilities, including cash, accounts receivable, accounts payable, and accrued expenses among others, approximate their reported carrying values because of their short-term nature. The assets invested for self-insurance are certificates of deposit and money market funds--classified as Level 1--based on quoted market prices of the identical underlying securities in active markets. Financial instruments classified as noncurrent liabilities and their carrying values and fair values were as follows: December 31, 2018 December 31, 2017 Carrying Value Fair Value Carrying Value Fair Value Revolving credit facility, noncurrent $ 93,500 $ 93,500 $ 100,000 $ 100,000 Senior unsecured notes 56,000 56,002 12,000 12,389 Term loans, noncurrent 6,662 6,868 7,935 10,038 Total $ 156,162 $ 156,370 $ 119,935 $ 122,427 The carrying value of our revolving credit facility approximates fair value--classified as Level 2--as the interest rates on the amounts outstanding are variable. The fair value of our senior unsecured notes and term loans--classified as Level 2--is determined based on expected future weighted-average interest rates with the same remaining maturities. Market Risk-- In the normal course of business, we are exposed to market risk related to changes in foreign currency exchange rates, changes in interest rates and changes in fuel prices. We do not hold or issue derivative financial instruments for trading or speculative purposes. In prior years, we have used derivative financial instruments to manage risk, in part, associated with changes in interest rates and changes in fuel prices. Presently, we are not engaged in any hedging or derivative activities.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Letters of Credit At December 31, 2018 , we were contingently liable to our principal banks in the amount of $72,565 for letters of credit outstanding primarily related to insurance coverage. V. Commitments and Contingencies (continued) Surety Bonds In certain circumstances, we have performance obligations that are supported by surety bonds in connection with our contractual commitments. Litigation We are party to a number of lawsuits, threatened lawsuits and other claims arising out of the normal course of business. We assess our liabilities and contingencies in connection with outstanding legal proceedings utilizing the latest information available. Where it is probable that we will incur a loss and the amount of the loss can be reasonably estimated, we record a liability in our consolidated financial statements. These legal accruals may be increased or decreased to reflect any relevant developments on a quarterly basis. Where a loss is not probable or the amount of the loss is not estimable, we do not record an accrual, consistent with applicable accounting guidance. Based on information currently available to us, advice of counsel, and available insurance coverage, we believe that our established accruals are adequate and the liabilities arising from the legal proceedings will not have a material adverse effect on our consolidated financial condition. We note, however, that in light of the inherent uncertainty in legal proceedings there can be no assurance that the ultimate resolution of a matter will not exceed established accruals. As a result, the outcome of a particular matter or a combination of matters may be material to our results of operations for a particular period, depending upon the size of the loss or our income for that particular period. In November 2017, a suit was filed in Savannah, Georgia state court (“State Court”) against Davey Tree, its subsidiary, Wolf Tree, Inc., a former Davey employee, two Wolf employees, and a former Wolf employee alleging various acts of negligence and seeking compensatory and punitive damages for wrongful death and assault and battery of the plaintiff’s husband, a Wolf Tree employee, who was shot and killed in August 2017. The case was mediated unsuccessfully in December 2018 and was set for trial on January 22, 2019. In July 2018, a related survival action was filed by the deceased’s estate against Davey Tree, its subsidiary, Wolf Tree, Inc., and four current and former employees in Savannah, Georgia, which arises out of the same allegations, seeks compensatory and punitive damages and also includes three RICO claims under Georgia law seeking compensatory damages, treble damages, and punitive damages. The 2018 case was removed to the United States District Court for the Southern District of Georgia, Savannah Division, on August 2, 2018 (“Federal Court”). The Company filed a motion to dismiss the RICO claims. Plaintiffs filed a motion to remand the case to state court, which the Company has opposed. The motions are pending. On December 6, 2018, a former Wolf Tree employee pled guilty to conspiracy to conceal, harbor, and shield illegal aliens. On December 21, 2018, the United States federal prosecutors filed a motion to stay both actions on the grounds that on December 13, 2018, an indictment was issued charging two former Wolf employees and one other individual with various crimes, including conspiracy to murder the deceased. On December 17, 2018, the United States Attorney’s Office for the Southern District of Georgia informed the Company and Wolf Tree that they are also under investigation for potential violations of immigration and other laws relating to the subject matter of the ongoing criminal investigation referenced above. The Company and Wolf Tree are cooperating with the investigation. On December 28, 2018, the State Court granted the United States’ motion to stay but indicated that it would nonetheless consider certain pending matters, including: (1) Plaintiff and a co-defendant’s motions that Davey Tree be forced to produce privileged documents and testimony, which had been submitted to a Special Master for recommendation; and (2) the Defendants’ motions for summary judgment. On January 11, 2019, the Special Master issued his recommendation that both Plaintiff and the co-defendant’s motions to force Davey to disclose privileged information be denied. The State Court judge has not yet moved on the recommendation. On January 29, 2019, the State Court heard oral argument on Defendants’ motions for summary judgment, and the motions remain pending. On January 28, 2019, the Federal Court also granted the United States’ motion to stay. On January 29, 2019, the State Court ordered the parties to return to mediation; the case is now set for mediation on April 17, 2019. In both cases, the Company has denied all liability and is vigorously defending the action. It also has retained separate counsel for some of the individual defendants, each of whom has denied all liability and also is vigorously defending the action.

Quarterly Results of Operations

Quarterly Results of Operations	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations (Unaudited)	Quarterly Results of Operations (Unaudited) The following is a summary of the results of operations for each quarter of 2018 and 2017 . We have given retroactive consideration to the two-for-one stock split of our common shares effective June 1, 2017. Fiscal 2018, Three Months Ended Mar 31 Jun 30 Sep 29 Dec 31 Revenues $ 208,651 $ 270,649 $ 265,318 $ 280,173 Gross profit (revenues less costs and expenses, operating) 64,028 102,967 94,193 98,215 Income (loss) from operations (5,666 ) 29,800 14,585 16,971 Net income (loss) (6,627 ) 21,714 8,384 4,506 Net income (loss) per share -- Basic $ (.26 ) $ .94 $ .35 $ .12 Net income (loss) per share -- Diluted $ (.26 ) $ .89 $ .34 $ .13 ESOT valuation per share $ 19.10 $ 19.70 $ 19.70 $ 21.10 Fiscal 2017, Three Months Ended Apr 1 Jul 1 Sep 30 Dec 31 Revenues $ 192,813 $ 245,037 $ 249,588 $ 228,520 Gross profit (revenues less costs and expenses, operating) 59,154 93,512 91,973 83,986 Income (loss) from operations (3,995 ) 25,659 19,049 11,478 Net income (loss) (3,887 ) 14,223 10,237 1,547 Net income (loss) per share -- Basic $ (.15 ) $ .57 $ .41 $ .04 Net income (loss) per share -- Diluted $ (.15 ) $ .55 $ .39 $ .04 ESOT valuation per share $ 17.60 $ 18.30 $ 18.30 $ 19.10 Fourth quarters of 2018 and 2017 include adjustments to casualty insurance expense that had the effect of decreasing gross profit in 2018 by $7,324 and increasing gross profit in 2017 by $2,735.

Subsequent Events (Notes)

Subsequent Events (Notes)	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent events [Text Block]	Subsequent Events PG&E Bankruptcy Filing On January 29, 2019, Pacific Gas & Electric Company, and its parent Company PG&E Corporation (“PG&E”), our largest utility customer, filed voluntary bankruptcy petitions under Chapter 11 of the United States Bankruptcy Code in the U.S. Bankruptcy Court for the Northern District of California. PG&E approximated 12% of revenues during 2018, 11% in 2017 and 12% in 2016. As a utility company, PG&E serves residential and industrial customers in California and has an ongoing obligation to continue to serve its customers, and we continue to perform under our contracts with PG&E post-petition. As of the date of the bankruptcy filing, we had pre-petition accounts receivable of approximately $13,000 which we believe to be collectible. While uncertainty exists as to the outcome of the bankruptcy proceedings, we do not anticipate PG&E's bankruptcy to have a material impact on our future cash flows and results of operations. AR Securitization On January 24, 2019, we amended our AR securitization facility to address insolvency proceedings, specifically those receivables from PG&E Corporation and its regulated utility subsidiary, Pacific Gas and Electric Company (collectively “Pacific Gas & Electric”), which filed voluntary bankruptcy petitions under Chapter 11 of the United States Bankruptcy Code in the U.S. Bankruptcy Court for the Northern District of California. Under the terms of the receivable financing agreement, receivables from Pacific Gas and Electric, while remaining in the securitized pool, will be considered ineligible and are excluded from performance ratios and reserves. Acquisition of Businesses Subsequent to December 31, 2018 and through March 11, 2019, we acquired two businesses approximating $3,950 with no liabilities assumed and debt issued of $1,092 . The acquired companies are in our Residential and Commercial segment in the Houston, Texas and Omaha, Nebraska markets. The effect of these acquisitions on our consolidated revenues and results of operations, either individually or in the aggregate, are not significant. F. Subsequent Events (continued) Issuance of Debt On February 5, 2019 we issued 4.00 % Senior Notes, Series B (the " 4.00 % Senior Notes") pursuant to the Note Purchase and Shelf Agreement in the aggregate principal amount of $25,000 . The notes are due September 21, 2028. Subsequent series of promissory notes may be issued pursuant to the Note Purchase and Shelf Agreement in an aggregate additional principal amount not to exceed $25,000 . The 4.00% Senior Notes are equal in right of payment with our revolving credit facility and all other senior unsecured obligations of the Company. Interest is payable semiannually and 5 equal, annual principal payments commence on September 21, 2024 (the sixth anniversary of issuance of the 3.99 % Senior Notes).

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Principles of consolidation and basis of presentation [Text Block]	Principles of Consolidation and Basis of Presentation --The consolidated financial statements include the accounts of Davey Tree and our wholly-owned subsidiaries and were prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as codified in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC"). Intercompany accounts and transactions have been eliminated in consolidation. Per Common Share Information --We have given retroactive consideration to the two -for-one stock split of our common shares effective June 1, 2017 including all common share and per share data.
Use of estimates in financial statement preparation [Policy Text Block]	Use of Estimates in Financial Statement Preparation --The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect reported amounts. Estimates are used for, but not limited to, accounts receivable valuation, depreciable lives of fixed assets, self-insurance accruals, stock valuation and revenue recognition. Actual results could differ from those estimates.
Property and equipment [Policy Text Block]	Property and Equipment --Property and equipment are stated at cost. Repair and maintenance costs are expensed as incurred. Depreciation is computed for financial reporting purposes by the straight-line method for land improvements, building and leasehold improvements and by the declining-balance method for equipment, based on the estimated useful lives of the assets, as follows: Land improvements 5 to 20 years Buildings 5 to 30 years Equipment 3 to 20 years Leasehold improvements Shorter of lease term or estimated useful life; ranging from 5-to-20 years
Intangible assets [Policy Text Block]	Intangible Assets --Intangible assets with finite lives, primarily customer lists, noncompete agreements and tradenames, are amortized by the straight-line method based on their estimated useful lives, ranging from one-to-ten years.
Long-lived assets [Policy Text Block]	Long-Lived Assets --We assess potential impairment to our long-lived assets, other than goodwill, when there is evidence that events or changes in circumstances have made recovery of the asset’s carrying value unlikely and the carrying amount of the asset exceeds the estimated future undiscounted cash flow. In the event the assessment indicates that the carrying amounts may not be recoverable, an impairment loss would be recognized to reduce the asset’s carrying amount to its estimated fair value based on the present value of the estimated future cash flows.
Goodwill [Policy Text Block]	Goodwill --Goodwill is recorded when the cost of acquired businesses exceeds the fair value of the identified net assets acquired. Goodwill is not amortized, but tested for impairment annually or when events or circumstances indicate that impairment may have occurred. Annually, we perform the impairment tests for goodwill during the fourth quarter. Impairment of goodwill is tested at the reporting-unit level, which for us are also our business segments. Impairment of goodwill is tested by comparing the reporting unit’s carrying value, including goodwill, to the fair value of the reporting unit. The fair values of the reporting units are estimated using discounted projected cash flows. If the carrying value of the reporting unit exceeds its fair value, goodwill is considered impaired and an impairment loss should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the carrying value of the goodwill allocated to that reporting unit. We conducted our annual impairment tests and determined that no impairment loss was required to be recognized in 2018 or for any prior periods. There were no events or circumstances from the date of our assessment through December 31, 2018 that would impact this conclusion.
Self-insurance accruals [Policy Text Block]	Self-Insurance Accruals --We are generally self-insured for losses and liabilities related primarily to workers’ compensation, vehicle liability and general liability claims. We use commercial insurance as a risk-reduction strategy to minimize catastrophic losses. Ultimate losses are accrued based upon estimates of the aggregate liability for claims incurred using certain actuarial assumptions followed in the insurance industry and based on Company-specific experience. Our self-insurance accruals include claims for which the ultimate losses will develop over a period of years. Accordingly, our estimates of ultimate losses can change as claims mature. Our accruals also are affected by changes in the number of new claims incurred and claim severity. The methods for estimating the ultimate losses and the total cost of claims were determined by third-party consulting actuaries; the resulting accruals are reviewed by management, and any adjustments arising from changes in estimates are reflected in income. The workers' compensation accruals are discounted as the amount and timing of cash payments related to those accruals are reliably determinable given the nature of workers' compensation benefits and the level of historical claim volume to support the actuarial assumptions and judgments used to derive the expected loss payment pattern. The workers' compensation accruals are discounted using an interest rate that approximates the long-term investment yields over the expected payment pattern of unpaid losses. Our self-insurance accruals are based on estimates and, while we believe that the amounts accrued are adequate and not excessive, the ultimate claims may be in excess of or less than the amounts provided.
Stock-based compensation [Policy Text Block]	Stock-Based Compensation -- Stock-based compensation cost for all share-based payment plans is measured at fair value on the date of grant and recognized over the employee service period on the straight-line recognition method for awards expected to vest. The fair value of all stock-based payment plans—stock option plans, stock-settled stock appreciation rights, and performance-based restricted stock units as well as our Employee Stock Purchase Plan—is determined by the number of awards granted and the price of our common stock. The fair value of each award is estimated on the date of grant using a binomial option-pricing model. The binomial model considers a range of assumptions related to volatility, risk-free interest rate and employee exercise behavior. Expected volatilities utilized in the binomial model are based on historical volatility of our share prices and other factors. Similarly, the dividend yield is based on historical experience and expected future changes. The binomial model also incorporates exercise assumptions based on an analysis of historical data. The expected life of the stock-based awards is derived from the output of the binomial model and represents the period of time that awards granted are expected to be outstanding.
Defined benefit pension plans [Policy Text Block]	Defined Benefit Pension Plans --We record annual expenses relating to our defined benefit pension plans based on calculations that include various actuarial assumptions, including discount rates and expected long-term rates of return on plan assets. Actuarial assumptions are reviewed annually with modifications made to the assumptions, if necessary, based on B. Summary of Significant Accounting Policies (continued) current rates and trends. The effects of the actuarial gains or losses are amortized over future service periods. The funded status (that is, the projected benefit obligation less the fair value of plan assets) for each plan is reported in our balance sheet using a December 31 measurement date. Changes in the funded status of the plans are recognized in the year in which the changes occur and reported in comprehensive income (loss).
Income taxes [Policy Text Block]	Income Taxes --We compute taxes on income in accordance with the tax rules and regulations where the income is earned. The income tax rates imposed by these taxing authorities vary. Taxable income may differ from pretax income for financial reporting purposes. We compute and recognize deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amounts and the tax bases of our assets and liabilities. Changes in tax rates and laws are reflected in income in the period when such changes are enacted. We account for uncertain tax positions by recognizing the financial statement effects of a tax position only when, based upon the technical merits, it is more-likely-than-not that the position will be sustained upon examination.
Earnings per share [Policy Text Block]	Earnings Per Share --Basic earnings per share is determined by dividing the income available to common shareholders by the weighted-average number of common shares outstanding. Diluted earnings per share is computed similarly to basic earnings per share except that the weighted-average number of shares is increased to include the effect of stock awards that were granted and outstanding during the period.
Revenue recognition [Policy Text Block]	Revenue Recognition --We recognize revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers, which we adopted on January 1, 2018, using the modified retrospective method. See Note C for further discussion of the adoption, including the impact on our 2018 financial statements. Performance obligations are satisfied as our services are provided to customers. See Note T for a detailed description of our revenue recognition policy.
Concentration of credit risk [Policy Text Block]	Concentration of Credit Risk --Credit risk represents the accounting loss that would be recognized if the counterparties failed to perform as contracted. The principal financial instruments subject to credit risk follow: Cash --To limit our exposure, we transact our business and maintain banking relationships with high credit-quality financial institutions. Accounts Receivable --Our residential and commercial customers are located geographically throughout the United States and Canada and, as to commercial customers, within differing industries; thus, minimizing credit risk. The credit exposure of utility services customers is directly affected by conditions within the utility industries as well as the financial condition of individual customers. One utility customer approximated 12% of revenues during 2018 , 11% in 2017 and 12% in 2016 . To reduce credit risk, we evaluate the credit of customers, but generally do not require advance payments or collateral. Exposure to losses on receivables is principally dependent on each customer’s financial condition.
Foreign currency translation and transactions [Policy Text Block]	Foreign Currency Translation and Transactions --Assets and liabilities of our Canadian operations are translated into U.S. dollars using year-end exchange rates, and revenues and expenses are translated using exchange rates as determined throughout the year. Gains or losses resulting from translation are included in the consolidated balance sheet, classified in shareholders’ equity as a separate component of accumulated other comprehensive income (loss). Gains or losses resulting from Canadian-dollar transactions with the Canadian operations are converted to U.S. dollars at the rates of exchange prevailing at the dates of the transactions. The effect of the transactions gain or loss is classified in the statement of operations as a component of other nonoperating income (expense), net.
Interst rate risk management [Policy Text Block]	Interest Rate Risk Management --We have entered into interest rate contracts, from time-to-time, with the objective of altering interest rate exposures related to variable rate debt. In the interest rate contracts, we have agreed with a financial institution to exchange, at specified intervals, the difference between fixed and floating interest amounts calculated on an agreed-upon notional principal amount. During the year ended December 31, 2018, we did not enter into any interest rate contracts.
Comprehensive income (loss) [Policy Text Block]	Comprehensive Income (Loss) --Comprehensive income (loss) includes net income and other comprehensive income or loss. Other comprehensive income (loss) refers to revenues, expenses, gains and losses that under U.S. GAAP are included in comprehensive income but are excluded from net income as these amounts are recorded directly as an adjustment to shareholders’ equity, net of tax.
Business combinations [Policy Text Block]	The net assets of the businesses acquired are accounted for under the acquisition method and were recorded at their fair values at the dates of acquisition.
Commitments and contingencies [Policy Text Block]	We are party to a number of lawsuits, threatened lawsuits and other claims arising out of the normal course of business. We assess our liabilities and contingencies in connection with outstanding legal proceedings utilizing the latest information available. Where it is probable that we will incur a loss and the amount of the loss can be reasonably estimated, we record a liability in our consolidated financial statements. These legal accruals may be increased or decreased to reflect any relevant developments on a quarterly basis. Where a loss is not probable or the amount of the loss is not estimable, we do not record an accrual, consistent with applicable accounting guidance.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Property, plant and equipment [Table Text Block]	Depreciation is computed for financial reporting purposes by the straight-line method for land improvements, building and leasehold improvements and by the declining-balance method for equipment, based on the estimated useful lives of the assets, as follows: Land improvements 5 to 20 years Buildings 5 to 30 years Equipment 3 to 20 years Leasehold improvements Shorter of lease term or estimated useful life; ranging from 5-to-20 years

Accounts Receivable, Net and _2

Accounts Receivable, Net and Supplemental Balance Sheet Information (Tables)	12 Months Ended
	Dec. 31, 2018
Accounts Receivable, Net and Supplemental Balance Sheet Information [Abstract]
Schedule of accounts receivable [Table Text Block]	Accounts receivable, net, consisted of the following: December 31, 2018 2017 Accounts receivable $ 158,556 $ 143,244 Unbilled receivables 40,671 29,895 199,227 173,139 Less allowances for doubtful accounts 3,321 4,468 $ 195,906 $ 168,671
Schedule of other current assets [Table Text Block]	The following items comprise the amounts included in the balance sheets: December 31, Other current assets 2018 2017 Refundable income taxes $ 1,625 $ 587 Other 932 784 Total $ 2,557 $ 1,371
Schedule of other assets, noncurrent [Table Text Block]	December 31, Other assets, noncurrent 2018 2017 Assets invested for self-insurance $ 15,379 $ 19,422 Investment--cost-method affiliate 1,218 1,218 Deferred income taxes 573 4,815 Other 4,599 3,701 Total $ 21,769 $ 29,156
Schedule of accrued expenses [Table Text Block]	December 31, Accrued expenses 2018 2017 Employee compensation $ 24,086 $ 20,794 Accrued compensated absences 9,711 9,267 Self-insured medical claims 3,343 3,193 Customer advances, deposits 1,322 1,672 Income taxes payable 31 3,443 Taxes, other than income 2,546 2,279 Other 3,022 2,168 Total $ 44,061 $ 42,816
Schedule of other liabilities, noncurrent [Table Text Block]	December 31, Other liabilities, noncurrent 2018 2017 Pension and retirement plans $ 6,138 $ 14,759 Other 3,987 5,207 Total $ 10,125 $ 19,966

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental cash flow information [Table Text Block]	Supplemental cash flow information follows: Year Ended December 31, Supplemental cash flow information 2018 2017 2016 Interest paid $ 6,375 $ 5,096 $ 4,329 Income taxes paid, net 11,514 10,005 10,578 Noncash transactions: Debt issued for purchases of businesses $ 2,402 $ 3,099 $ 875 Detail of acquisitions: Assets acquired: Accounts receivable $ 1,311 $ 1,753 $ — Operating supplies 23 — 157 Prepaid expense 89 128 55 Equipment 4,079 1,904 2,485 Other assets 7 52 — Intangible assets 4,895 4,296 1,374 Goodwill 2,840 5,131 817 Liabilities assumed (2,381 ) (2,713 ) (216 ) Debt issued for purchases of businesses (2,402 ) (3,099 ) (875 ) Cash paid $ 8,461 $ 7,452 $ 3,797

Identified Intangible Assets _2

Identified Intangible Assets and Goodwill, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of acquired finite-lived intangible assets by major class [Table Text Block]	The carrying amount of the intangible assets and goodwill acquired in connection with our acquisitions were as follows: Weighted-Average Amortization Period (Years) December 31, 2018 December 31, 2017 Carrying Amount Accumulated Amortization Carrying Amount Accumulated Amortization Amortized intangible assets: Customer lists/relationships 3.6 years $ 25,179 $ 18,251 $ 21,487 $ 16,846 Employment-related 2.8 years 8,133 6,954 7,333 6,624 Tradenames 3.7 years 6,858 5,435 5,978 5,134 Total 40,170 $ 30,640 34,798 $ 28,604 Less accumulated amortization 30,640 28,604 Intangible assets, net 9,530 6,194 Goodwill 37,971 35,477 $ 47,501 $ 41,671
Schedule of goodwill [Table Text Block]	The changes in the carrying amounts of goodwill, by segment, for the years ended December 31, 2018 and December 31, 2017 follow: Balance at January 1, 2018 Acquisitions Translation and Other Adjustments Balance at December 31, 2018 Utility $ 3,424 $ 1,487 $ — $ 4,911 Residential and Commercial 32,053 1,353 (346 ) 33,060 Total $ 35,477 $ 2,840 $ (346 ) $ 37,971 Balance at January 1, 2017 Acquisitions Translation and Other Adjustments Balance at December 31, 2017 Utility $ 3,424 $ — $ — $ 3,424 Residential and Commercial 26,881 5,131 41 32,053 Total $ 30,305 $ 5,131 $ 41 $ 35,477
Schedule of finite-lived intangible assets, future amortization expense [Table Text Block]	The estimated aggregate amortization expense of intangible assets, as of December 31, 2018 , in each of the next five years follows: Estimated Future Amortization Expense Year ending December 31, 2019 $ 2,197 2020 2,011 2021 1,569 2022 1,339 2023 1,209 Thereafter 1,205 $ 9,530

Short and Long-Term Debt and _2

Short and Long-Term Debt and Commitments Related to Letters of Credit (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of short-term debt [Table Text Block]	Short-term debt consisted of the following: December 31, 2018 2017 Notes payable $ — $ 149 Current portion of long-term debt 22,514 16,166 $ 22,514 $ 16,315
Schedule of long-term debt instruments [Table Text Block]	Long-term debt consisted of the following: December 31, 2018 2017 Revolving credit facility Swing-line borrowings $ 2,500 $ — LIBOR borrowings 91,000 100,000 93,500 100,000 5.09% Senior unsecured notes 12,000 18,000 3.99% Senior unsecured notes 50,000 — Term loans 23,176 16,242 178,676 134,242 Less debt issuance costs 599 725 Less current portion 22,514 16,166 $ 155,563 $ 117,351

Self-Insurance Accruals (Tables

Self-Insurance Accruals (Tables)	12 Months Ended
	Dec. 31, 2018
Self-Insurance Accruals [Abstract]
Schedule of self-insurance accruals [Table Text Block]	Components of our self-insurance accruals for workers’ compensation, vehicle liability and general liability follow: December 31, 2018 2017 Workers' compensation $ 41,577 $ 40,764 Present value discount 3,099 2,346 38,478 38,418 Vehicle liability 13,342 5,536 General liability 31,965 23,740 Total 83,785 67,694 Less current portion 27,434 23,782 Noncurrent portion $ 56,351 $ 43,912
Schedule of changes in self-insurance accruals [Table Text Block]	The changes in our self-insurance accruals and the discount rate used for the workers’ compensation accrual are summarized in the table below. December 31, 2018 2017 Balance, beginning of year $ 67,694 $ 62,838 Provision for claims 51,685 34,884 Payment of claims (35,594 ) (30,028 ) Balance, end of year $ 83,785 $ 67,694 Workers' compensation discount rate 2.50 % 2.00 % The increase in the provision for claims primarily relates to increases for certain vehicle and general liability claims that are anticipated to settle in the future at or near our retention levels.

Lease Obligations (Tables)

Lease Obligations (Tables)	12 Months Ended
	Dec. 31, 2018
Leases [Abstract]
Schedule of assets acquired under capital leases [Table Text Block]	Assets acquired under capital leases and included in property and equipment consisted of the following: December 31, 2018 2017 Equipment $ 6,534 $ 3,481 Less accumulated amortization 1,797 805 $ 4,737 $ 2,676
Schedule of future minimum lease payments for capital leases [Table Text Block]	Minimum rental commitments under all capital and noncancelable operating leases, as of December 31, 2018 , were as follows: Lease Obligations Minimum lease obligations Capital Operating Year ending December 31, 2019 $ 1,426 $ 14,023 2020 1,371 11,272 2021 1,183 7,712 2022 272 5,129 2023 71 2,060 2024 and after — 1,923 Total minimum lease payments 4,323 $ 42,119 Amounts representing interest 116 Present value of net minimum lease payments 4,207 Less current portion 1,345 Long-term capital lease obligations, December 31, 2018 $ 2,862
Schedule of future minimum rental payments for operating leases [Table Text Block]	Minimum rental commitments under all capital and noncancelable operating leases, as of December 31, 2018 , were as follows: Lease Obligations Minimum lease obligations Capital Operating Year ending December 31, 2019 $ 1,426 $ 14,023 2020 1,371 11,272 2021 1,183 7,712 2022 272 5,129 2023 71 2,060 2024 and after — 1,923 Total minimum lease payments 4,323 $ 42,119 Amounts representing interest 116 Present value of net minimum lease payments 4,207 Less current portion 1,345 Long-term capital lease obligations, December 31, 2018 $ 2,862

Common Shares, Redeemable Com_2

Common Shares, Redeemable Common Shares and Preferred Shares (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of stock by class [Table Text Block]	Common and Redeemable Shares Outstanding -- The table below reconciles the activity of the common and redeemable shares outstanding: Common Shares Net of Treasury Shares Redeemable Shares Total Shares outstanding, December 31, 2016 17,866,236 7,056,904 24,923,140 Shares purchased (807,718 ) (890,009 ) (1,697,727 ) Shares sold 362,674 300,132 662,806 Stock subscription offering, employee cash purchases 90,645 — 90,645 Options exercised 241,995 — 241,995 Shares outstanding, December 31, 2017 17,753,832 6,467,027 24,220,859 Shares purchased (1,530,528 ) (1,106,415 ) (2,636,943 ) Shares sold 679,197 281,543 960,740 Stock subscription offering, employee cash purchases 129,245 — 129,245 Options exercised 206,751 — 206,751 Shares outstanding, December 31, 2018 17,238,497 5,642,155 22,880,652

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of accumulated other comprehensive income (loss) [Table Text Block]	The following summarizes the components of other comprehensive income (loss) accumulated in shareholders’ equity: Foreign Currency Translation Adjustments Defined Benefit Pension Plans Accumulated Other Comprehensive Income (Loss) Balance at January 1, 2016 $ (6,244 ) $ (7,150 ) $ (13,394 ) Unrealized gains (losses) 744 — 744 Amounts reclassified from accumulated other comprehensive income (loss) — 2,844 2,844 Tax effect — (1,137 ) (1,137 ) Unrecognized amounts from defined benefit pension plans — (2,032 ) (2,032 ) Tax effect — 813 813 Net of tax amount 744 488 1,232 Balance at December 31, 2016 $ (5,500 ) $ (6,662 ) $ (12,162 ) Unrealized gains (losses) 2,195 — 2,195 Amounts reclassified from accumulated other comprehensive income (loss) — 4,822 4,822 Tax effect — (1,962 ) (1,962 ) Unrecognized amounts from defined benefit pension plans — (2,169 ) (2,169 ) Tax effect — 883 883 Net of tax amount 2,195 1,574 3,769 Balance at December 31, 2017 $ (3,305 ) $ (5,088 ) $ (8,393 ) Unrealized gains (losses) (2,514 ) — (2,514 ) Amounts reclassified from accumulated other comprehensive income (loss) — 6,291 6,291 Tax effect — (145 ) (145 ) Unrecognized amounts from defined benefit pension plans — (279 ) (279 ) Tax effect — 6 6 Net of tax amount (2,514 ) 5,873 3,359 Balance at December 31, 2018 $ (5,819 ) $ 785 $ (5,034 )

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of share-based compensation arrangements by share-based payment award [Table Text Block]	Stock-based compensation expense under all share-based payment plans—our Employee Stock Purchase Plan, stock option plans, stock-settled stock appreciation rights, and performance-based restricted stock units—included in the results of operations follows: Year Ended December 31, 2018 2017 2016 Compensation expense, all share-based payment plans $ 3,370 $ 4,049 $ 2,811 Income tax benefit 602 1,315 823
Schedule of share-based compensation, stock-settled stock appreciation rights award activity [Table Text Block]	The following table summarizes the SSARs as of December 31, 2018 : Stock-Settled Stock Appreciation Rights Number of Rights Weighted- Average Award Date Value Weighted- Average Remaining Contractual Life Unrecognized Compensation Cost Aggregate Intrinsic Value Unvested, January 1, 2018 448,180 $ 3.10 Granted 121,243 3.84 Forfeited — — Vested (188,441 ) 2.93 Unvested, December 31, 2018 380,982 $ 3.42 2.4 years $ 924 $ 7,505
Schedule of share-based compensation, restricted stock units award activity [Table Text Block]	The following table summarizes restricted stock units as of December 31, 2018 : Restricted Stock Units Number of Stock Units Weighted- Average Grant Date Value Weighted- Average Remaining Contractual Life Unrecognized Compensation Cost Aggregate Intrinsic Value Unvested, January 1, 2018 290,666 $ 14.41 Granted 44,926 18.55 Forfeited — — Vested (87,754 ) 12.94 Unvested, December 31, 2018 247,838 $ 15.68 1.9 years $ 1,727 $ 4,882 Employee PRSUs 209,186 $ 15.40 2.2 years $ 1,401 $ 4,121 Nonemployee Director RSUs 38,652 $ 17.17 1.3 years $ 326 $ 761
Schedule of share-based payment award, stock options, valuation assumptions [Table Text Block]	The fair values of stock-based awards granted were estimated at the dates of grant with the following weighted-average assumptions: Year Ended December 31, 2018 2017 2016 Volatility rate 10.1 % 10.3 % 10.6 % Risk-free interest rate 2.7 % 2.2 % 1.8 % Expected dividend yield .7 % .7 % .7 % Expected life of awards (years) 9.2 8.9 9.5
Schedule of share-based compensation, stock options, activity [Table Text Block]	The following table summarizes activity under the stock option plans for the year ended December 31, 2018 : Stock Options Number of Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life Unrecognized Compensation Cost Aggregate Intrinsic Value Outstanding, January 1, 2018 1,528,615 $ 13.05 Granted 143,250 19.10 Exercised (147,321 ) 9.93 Forfeited (58,280 ) 13.29 Outstanding, December 31, 2018 1,466,264 $ 13.94 5.9 years $ 1,393 $ 8,446 Exercisable, December 31, 2018 889,814 $ 11.79 4.7 years $ 7,037
Schedule of share-based compensation, shares authorized under stock option plans, by exercise price range [Table Text Block]	Information regarding the stock options outstanding at December 31, 2018 is summarized below: Stock Options Exercise Price Number Outstanding Weighted-Average Remaining Contractual Life Weighted- Average Exercise Price Number Exercisable Weighted- Average Exercise Price Employee options: $ 8.00 88,413 0.8 years $ 8.00 88,413 $ 8.00 8.30 107,000 1.8 years 8.30 107,000 8.30 11.60 270,414 4.5 years 11.60 270,414 11.60 13.20 284,822 5.5 years 13.20 211,422 13.20 15.05 219,965 6.5 years 15.05 112,765 15.05 16.35 230,800 7.5 years 16.35 77,800 16.35 17.60 129,300 8.5 years 17.60 22,000 17.60 19.10 135,550 9.5 years 19.10 — 19.10 1,466,264 5.9 years $ 13.94 889,814 $ 11.79

Defined Benefit Pension Plans (

Defined Benefit Pension Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of changes in projected benefit obligations [Table Text Block]	The change in benefit obligations and the fair value of plans assets follows: December 31, 2018 2017 Change in benefit obligation Projected benefit obligation at beginning of year $ 19,403 $ 24,833 Service cost 400 530 Interest cost 718 1,002 Actuarial (gains)/losses (77 ) 1,865 Amendments — — Settlements (13,118 ) (8,400 ) Benefits paid (262 ) (427 ) Projected benefit obligation at end of year $ 7,064 $ 19,403 Accumulated benefit obligation at end of year $ 7,064 $ 19,403
Schedule of changes in fair value of plan sssets [Table Text Block]	December 31, 2018 2017 Change in fair value of plan assets Fair value of plan assets at beginning of year $ 7,105 $ 11,509 Actual return on plan assets 239 845 Plan expenses, including PBGC premiums (364 ) (513 ) Employer contributions 10,158 4,091 Settlements (13,118 ) (8,400 ) Benefits paid (262 ) (427 ) Fair value of plan assets at end of year $ 3,758 $ 7,105
Schedule of net funded status [Table Text Block]	December 31, 2018 2017 Funded status of the plans Fair value of plan assets $ 3,758 $ 7,105 Projected benefit obligation 7,064 19,403 Funded status of the plans $ (3,306 ) $ (12,298 ) December 31, 2018 2017 Funded status by plan ERP $ (332 ) $ (9,084 ) SERP (2,564 ) (2,759 ) Restoration Plan (410 ) (455 ) $ (3,306 ) $ (12,298 )
Schedule of amounts recognized in balance sheet [Table Text Block]	December 31, 2018 2017 Amounts reported in the consolidated balance sheets Current liability $ (187 ) $ (175 ) Noncurrent liability (3,119 ) (12,123 ) Funded status of the plans $ (3,306 ) $ (12,298 )
Schedule of amounts in accumulated other comprehensive income [Table Text Block]	Amounts included in accumulated other comprehensive income (loss), related to our defined benefit pension plans follow: At December 31, 2018 At December 31, 2017 Pretax Net of Tax Pretax Net of Tax Amounts reported in accumulated other comprehensive income Unrecognized net actuarial loss $ 2,139 $ (714 ) $ 8,086 $ 4,919 Unrecognized prior service cost 214 (71 ) 278 169 $ 2,353 $ (785 ) $ 8,364 $ 5,088
Schedule of amounts in accumulated other comprehensive income (loss) to be recognized over next fiscal year [Table Text Block]	P. Defined Benefit Pension Plans (continued) The total amortization associated with these amounts that is expected to be recognized in net periodic benefit expense for 2019 follows: Year ending December 31, 2019 Pretax Net of Tax Amortization of Costs Expected to be Recognized Next Year Unrecognized net actuarial loss $ 175 $ 131 Unrecognized prior service cost 64 48 $ 239 $ 179
Schedule of accumulated benefit obligations in excess of fair value of plan assets [Table Text Block]	The aggregate projected benefit obligation, accumulated benefit obligation and fair value of plan assets for plans in which the fair value of plan assets is less than either the projected benefit obligation or accumulated benefit obligation follow: December 31, 2018 2017 For pension plans with accumulated benefit obligations in excess of plan assets Projected benefit obligation $ 7,064 $ 19,403 Accumulated benefit obligation 7,064 19,403 Fair value of plan assets 3,758 7,105
Schedule of assumptions used [Table Text Block]	The actuarial assumptions follow. The discount rates were used to measure the year-end benefit obligation and compute pension expense for the subsequent year. December 31, 2018 2017 2016 Actuarial assumptions Discount rate 4.35 % 3.70 % 4.20 % Expected long-term rate of return on plan assets 2.50 2.50 5.00
Components of pension expense (income) [Table Text Block]	Net periodic benefit expense (income) associated with the defined benefit pension plans included the following components: Year Ended December 31, 2018 2017 2016 Components of pension expense (income) Service costs--increase in benefit obligation earned $ 400 $ 530 $ 370 Interest cost on projected benefit obligation 718 1,002 1,243 Expected return on plan assets (231 ) (638 ) (1,044 ) Curtailment loss — — — Settlement loss 5,499 3,849 2,346 Amortization of net actuarial loss 728 909 951 Amortization of prior service cost 64 64 — Net pension expense of defined benefit pension plans $ 7,178 $ 5,716 $ 3,866
Schedule of allocation of plan assets [Table Text Block]	The fair values of our pension plan assets at December 31, 2018 by asset category, using the three-level hierarchy of fair value inputs, were as follows: Fair Value Measurements at December 31, 2018 Using: Description Total Carrying Value at December 31, 2018 Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Asset Category Money market funds $ 3,758 $ 3,758 $ — U.S. large-cap equities Growth — — — Value — — — U.S. small/mid-cap equities Growth — — — Value — — — International equities Growth — — — Value — — — Fixed income — — — Multiclass world-allocation mutual funds — — — $ 3,758 $ — $ 3,758 $ — P. Defined Benefit Pension Plans (continued) The fair values of our pension plan assets at December 31, 2017 by asset category, using the three-level hierarchy of fair value inputs, were as follows: Fair Value Measurements at December 31, 2017 Using: Description Total Carrying Value at December 31, 2017 Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Asset Category Money market funds $ 897 $ — $ 897 $ — U.S. large-cap equities Growth 576 576 — — Value 542 542 — — U.S. small/mid-cap equities Growth 246 246 — — Value 247 247 — — International equities Growth 376 376 — — Value 366 366 — — Fixed income 3,070 3,070 — — Multiclass world-allocation mutual funds 785 785 — — $ 7,105 $ 6,208 $ 897 $ —
Schedule of expected benefit payments [Table Text Block]	The benefits, as of December 31, 2018 , expected to be paid to defined-benefit plan participants in each of the next five years, and in the aggregate for the five years thereafter, follows: Participants Benefits Estimated future payments Year ending December 31, 2019 $ 356 2020 379 2021 384 2022 386 2023 389 Years 2024 to 2028 1,986
Schedule of multiemployer plans [Table Text Block]	Our participation in the multiemployer defined benefit pension plans is summarized in the table below. The “EIN/Pension Plan Number” column provides the Employer Identification Number (“EIN”) and the three-digit plan number. The most recent Pension Protection Act of 2006 (the “PPA”) zone status is from the Form 5500, “Annual Return/Report of Employee Benefit Plan,” filed by the plan and certified by the plan's actuary. The PPA zone status describes plans that are underfunded. Among other factors, plans in the “critical” red zone are generally less than 65% funded; plans in the “endangered” yellow zone are less than 80% funded; and, plans in the “safe” green zone are at least 80% funded. Pension Fund EIN/Pension Plan Number Pension Protection Act Zone Status FIP/RP Status Pending Implemented Davey Tree Contributions Surcharge Imposed Expiration Dates of Bargaining Agreement 2018 2017 2018 2017 2016 National Electric Benefit Fund 53-0181657/001 Green Green No $ 768 $ 785 $ 712 No Ranging from December 31, 2018 to December 31, 2022 Eighth District Electrical Pension Fund 84-6100393/001 Green Green No 142 102 90 No December 26, 2020 $ 910 $ 887 $ 802

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of income before income tax, domestic and foreign [Table Text Block]	Income before income taxes was attributable to the following sources: Year Ended December 31, 2018 2017 2016 United States $ 37,377 $ 38,800 $ 35,867 Canada 119 (806 ) 1,377 Total $ 37,496 $ 37,994 $ 37,244
Schedule of components of income tax expense (benefit) [Table Text Block]	The provision for income taxes follows: Year Ended December 31, 2018 2017 2016 Currently payable: Federal $ 3,165 $ 9,914 $ 12,216 State 2,290 2,469 2,286 Canadian 50 (262 ) 398 Total current 5,505 12,121 14,900 Deferred taxes 4,014 3,753 60 Total taxes on income $ 9,519 $ 15,874 $ 14,960
Schedule of effective income tax rate reconciliation [Table Text Block]	A reconciliation of the expected statutory U.S. federal rate to our actual effective income tax rate follows: Year Ended December 31, 2018 2017 2016 Statutory U.S. federal tax rate 21.0 % 35.0 % 35.0 % State income taxes, net of federal benefit 5.7 4.9 4.0 Effect of Canadian income taxes .1 .3 (.2 ) Nondeductible expenses 2.1 2.2 2.2 ESOP dividend deduction (.3 ) (.6 ) (.7 ) Uncertain tax adjustments and audit settlement (3.8 ) (.2 ) .2 Income tax reform - deferred rate remeasurement — 2.5 — All other, net .6 (2.3 ) (.3 ) Effective income tax rate 25.4 % 41.8 % 40.2 %
Deferred tax assets and liabilities, noncurrent [Table Text Block]	Significant components of our noncurrent net deferred tax assets and liabilities at December 31, were as follows: December 31, 2018 2017 Deferred tax assets: Self-insurance accruals $ 17,579 $ 14,186 Accrued compensated absences 1,565 1,747 Accrued expenses and other liabilities 742 798 Accrued stock compensation 1,772 1,571 Defined benefit pension plans 442 2,289 Foreign tax credit carryforward 2,117 605 Other future deductible amounts, net 3,271 3,661 27,488 24,857 Less deferred tax asset valuation allowance 1,683 — 25,805 24,857 Deferred tax liabilities: Intangibles 1,178 969 Prepaid expenses 3,160 2,300 Property and equipment 20,894 16,773 25,232 20,042 Net deferred tax assets--noncurrent $ 573 $ 4,815
Summary of unrecognized income tax benefits [Table Text Block]	The balance of unrecognized benefits and the amount of related interest and penalties at December 31, were as follows: December 31, 2018 2017 Unrecognized tax benefits $ 1,325 $ 2,581 Portion, if recognized, would reduce tax expense and effective tax rate 599 1,948 Accrued interest on unrecognized tax benefits 35 128
Schedule of unrecognized tax benefits roll forward [Table Text Block]	The changes in our unrecognized tax benefits are summarized in the table below: Year Ended December 31, 2018 2017 2016 Balance, beginning of year $ 2,581 $ 2,532 $ 2,557 Additions based on tax positions related to the current year 224 650 402 Additions for tax positions of prior years 20 (21 ) 51 Reductions for tax positions of prior years (1,500 ) — (39 ) Lapses in statutes of limitations — (580 ) (439 ) Balance, end of year $ 1,325 $ 2,581 $ 2,532

Earnings Per Share Information

Earnings Per Share Information (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of earnings per share calculation [Table Text Block]	Earnings per share is computed as follows (prior periods have been adjusted for the two-for-one stock split of our common shares effective June 1, 2017): Year Ended December 31, 2018 2017 2016 Income available to common shareholders: Net income $ 27,977 $ 22,120 $ 22,284 Weighted-average shares: Basic: Outstanding 23,698,478 24,793,086 25,378,600 Partially-paid share subscriptions 690,260 764,382 833,440 Basic weighted-average shares 24,388,738 25,557,468 26,212,040 Diluted: Basic from above 24,388,738 25,557,468 26,212,040 Incremental shares from assumed: Exercise of stock subscription purchase rights 141,287 146,453 142,746 Exercise of stock options and awards 950,593 993,141 892,568 Diluted weighted-average shares 25,480,618 26,697,062 27,247,354 Share data: Earnings per share--basic $ 1.15 $ .87 $ .85 Earnings per share--diluted $ 1.10 $ .83 $ .82

Operations by Business Segmen_2

Operations by Business Segment and Geographic Information Operations by business segment (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of segment reporting information, by segment [Table Text Block]	Information on reportable segments and reconciliation to the consolidated financial statements follows: Utility Services Residential Commercial Services All Other Reconciling Adjustments Consolidated Fiscal Year 2018 Revenues $ 537,484 $ 486,005 $ 1,302 $ — $ 1,024,791 Income (loss) from operations 32,370 47,812 (19,816 ) (4,676 ) (a) 55,690 Interest expense (7,039 ) (7,039 ) Interest income 350 350 Other income (expense), net (11,505 ) (11,505 ) Income before income taxes $ 37,496 Depreciation $ 29,526 $ 21,720 $ — $ 3,668 (b) $ 54,914 Amortization 211 1,842 — 2 2,055 Capital expenditures 32,148 22,256 — 6,006 60,410 Segment assets, total 239,426 208,369 — 78,828 (c) 526,623 Fiscal Year 2017 Revenues $ 466,727 $ 446,028 $ 3,203 $ — $ 915,958 Income (loss) from operations 18,223 41,158 (2,634 ) (4,556 ) (a) 52,191 Interest expense (4,886 ) (4,886 ) Interest income 292 292 Other income (expense), net (9,603 ) (9,603 ) Income before income taxes $ 37,994 Depreciation $ 27,928 $ 19,384 $ — $ 3,390 (b) $ 50,702 Amortization 122 2,240 — 22 2,384 Capital expenditures 26,910 23,199 — 6,991 57,100 Segment assets, total 189,662 197,698 — 85,775 (c) 473,135 Fiscal Year 2016 Revenues $ 433,379 $ 410,878 $ 1,421 $ — $ 845,678 Income (loss) from operations 19,256 36,640 (4,318 ) (2,711 ) (a) 48,867 Interest expense (4,393 ) (4,393 ) Interest income 255 255 Other income (expense), net (7,485 ) (7,485 ) Income before income taxes $ 37,244 Depreciation $ 26,855 $ 17,198 $ — $ 3,231 (b) $ 47,284 Amortization 135 2,136 — 35 2,306 Capital expenditures 28,660 21,819 — 6,167 56,646 Segment assets, total 171,220 166,858 — 85,861 (c) 423,939
Schedule of revenue from external customers and long-lived assets attributed to foreign countries by geographic area [Table Text Block]	Geographic Information -- The following presents revenues and long-lived assets by geographic territory: Year Ended December 31, 2018 2017 2016 Revenues United States $ 949,317 $ 847,540 $ 775,870 Canada 75,474 68,418 69,808 $ 1,024,791 $ 915,958 $ 845,678 December 31, 2018 2017 2016 Long-lived assets, net United States $ 251,181 $ 242,118 $ 224,727 Canada 20,374 21,893 20,439 $ 271,555 $ 264,011 $ 245,166

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue Recognition [Abstract]
Disaggregation of revenue [Table Text Block]	The following tables disaggregate our revenue for the year ended December 31, 2018 by major sources: Year Ended December 31, 2018 Utility Residential and Commercial All Other Consolidated Type of service: Tree and plant care $ 394,481 $ 290,940 $ (1,520 ) $ 683,901 Grounds maintenance — 117,498 — 117,498 Storm damage services 13,864 9,447 — 23,311 Consulting and other 129,139 68,120 2,822 200,081 Total revenues $ 537,484 $ 486,005 $ 1,302 $ 1,024,791 Geography: United States $ 499,242 $ 448,773 $ 1,302 $ 949,317 Canada 38,242 37,232 — 75,474 Total revenues $ 537,484 $ 486,005 $ 1,302 $ 1,024,791
Contract with customer, asset and liability [Table Text Block]	Net contract liabilities consisted of the following: December 31, December 31, Contract liabilities - current $ 2,907 $ 2,072 Contract liabilities - noncurrent 2,287 2,020 Net contract liabilities $ 5,194 $ 4,092

Fair Value Measurements and F_2

Fair Value Measurements and Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value, assets measured on recurring basis [Table Text Block]	Our assets and liabilities measured at fair value on a recurring basis at December 31, 2018 and December 31, 2017 , were as follows: Fair Value Measurements at December 31, 2018 Using: Total Carrying Value at Quoted prices in active markets Significant other observable inputs Significant unobservable inputs Description December 31, 2018 (Level 1) (Level 2) (Level 3) Assets: Assets invested for self-insurance, classified as other assets, noncurrent $ 15,379 $ 15,379 $ — $ — Defined benefit pension plan assets 3,758 — 3,758 — Liabilities: Deferred compensation $ 2,459 $ — $ 2,459 $ — U. Fair Value Measurements and Financial Instruments (continued) Fair Value Measurements at December 31, 2017 Using: Total Carrying Value at Quoted prices in active markets Significant other observable inputs Significant unobservable inputs Description December 31, 2017 (Level 1) (Level 2) (Level 3) Assets: Assets invested for self-insurance, classified as other assets, noncurrent $ 19,422 $ 19,422 $ — $ — Defined benefit pension plan assets 7,105 6,208 897 — Liabilities: Deferred compensation $ 2,146 $ — $ 2,146 $ —
Fair value, by balance sheet grouping [Table Text Block]	Financial instruments classified as noncurrent liabilities and their carrying values and fair values were as follows: December 31, 2018 December 31, 2017 Carrying Value Fair Value Carrying Value Fair Value Revolving credit facility, noncurrent $ 93,500 $ 93,500 $ 100,000 $ 100,000 Senior unsecured notes 56,000 56,002 12,000 12,389 Term loans, noncurrent 6,662 6,868 7,935 10,038 Total $ 156,162 $ 156,370 $ 119,935 $ 122,427

Quarterly Results of Operatio_2

Quarterly Results of Operations Quarterly Results of Operations (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information [Table Text Block]	The following is a summary of the results of operations for each quarter of 2018 and 2017 . We have given retroactive consideration to the two-for-one stock split of our common shares effective June 1, 2017. Fiscal 2018, Three Months Ended Mar 31 Jun 30 Sep 29 Dec 31 Revenues $ 208,651 $ 270,649 $ 265,318 $ 280,173 Gross profit (revenues less costs and expenses, operating) 64,028 102,967 94,193 98,215 Income (loss) from operations (5,666 ) 29,800 14,585 16,971 Net income (loss) (6,627 ) 21,714 8,384 4,506 Net income (loss) per share -- Basic $ (.26 ) $ .94 $ .35 $ .12 Net income (loss) per share -- Diluted $ (.26 ) $ .89 $ .34 $ .13 ESOT valuation per share $ 19.10 $ 19.70 $ 19.70 $ 21.10 Fiscal 2017, Three Months Ended Apr 1 Jul 1 Sep 30 Dec 31 Revenues $ 192,813 $ 245,037 $ 249,588 $ 228,520 Gross profit (revenues less costs and expenses, operating) 59,154 93,512 91,973 83,986 Income (loss) from operations (3,995 ) 25,659 19,049 11,478 Net income (loss) (3,887 ) 14,223 10,237 1,547 Net income (loss) per share -- Basic $ (.15 ) $ .57 $ .41 $ .04 Net income (loss) per share -- Diluted $ (.15 ) $ .55 $ .39 $ .04 ESOT valuation per share $ 17.60 $ 18.30 $ 18.30 $ 19.10 Fourth quarters of 2018 and 2017 include adjustments to casualty insurance expense that had the effect of decreasing gross profit in 2018 by $7,324 and increasing gross profit in 2017 by $2,735.

Our Business Reportable segment

Our Business Reportable segments (Details)	12 Months Ended
	Dec. 31, 2018
Number of reportable segments	2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies Stock split adjustment (Details)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Stock split, conversion ratio	2

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2018
Minimum [Member]
Property, plant and equipment [Line Items]
Intangible assets, estimated useful life (in years)	1 year
Maximum [Member]
Property, plant and equipment [Line Items]
Intangible assets, estimated useful life (in years)	10 years
Land improvements [Member] | Minimum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	5 years
Land improvements [Member] | Maximum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	20 years
Buildings [Member] | Minimum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	5 years
Buildings [Member] | Maximum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	30 years
Equipment [Member] | Minimum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	3 years
Equipment [Member] | Maximum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	20 years
Leasehold improvements [Member] | Minimum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	5 years
Leasehold improvements [Member] | Maximum [Member]
Property, plant and equipment [Line Items]
Property and equipment, estimated useful lives (in years)	20 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies Goodwill impairment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Goodwill, impairment loss	$ 0	$ 0	$ 0

Recent Accounting Guidance Rece

Recent Accounting Guidance Recent accounting guidance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounting Standards Update 2017-07 [Member]
Pension cost	$ 5,186	$ 3,496

Business Combinations (Details)

Business Combinations (Details) - USD ($) $ in Thousands	2 Months Ended	12 Months Ended
	Mar. 11, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business acquisition [Line Items]
Investments in businesses		$ 13,244	$ 13,264	$ 4,888
Liabilities assumed		2,381	2,713	216
Debt issued		2,402	3,099	875
Goodwill		2,840	5,131	817
Goodwill acquired during period, tax deductible amount		$ 2,840	$ 5,131	$ 1,410
Subsequent event [Member]
Business acquisition [Line Items]
Liabilities assumed	$ 0
Debt issued	$ 1,092
Customer lists/relationships
Business acquisition [Line Items]
Intangible assets, estimated useful life (in years)		7 years
Tradenames
Business acquisition [Line Items]
Intangible assets, estimated useful life (in years)		7 years
Noncompete agreements [Member]
Business acquisition [Line Items]
Intangible assets, estimated useful life (in years)		5 years

Accounts Receivable, Net and _3

Accounts Receivable, Net and Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, net
Accounts receivable	$ 158,556	$ 143,244
Unbilled receivables	40,671	29,895
Accounts receivable, gross, current	199,227	173,139
Less allowances for doubtful accounts	3,321	4,468
Accounts receivable, net	195,906	168,671
Other current assets
Refundable income taxes	1,625	587
Other	932	784
Other current assets, total	2,557	1,371
Other assets, noncurrent
Assets invested for self-insurance	15,379	19,422
Investment--cost-method affiliate	1,218	1,218
Deferred income taxes	573	4,815
Other	4,599	3,701
Other assets, noncurrent, total	21,769	29,156
Accrued expenses
Employee compensation	24,086	20,794
Accrued compensated absences	9,711	9,267
Self-insured medical claims	3,343	3,193
Customer advances, deposits	1,322	1,672
Income taxes payable	31	3,443
Taxes, other than income	2,546	2,279
Other	3,022	2,168
Accrued expenses, total	44,061	42,816
Other liabilities, noncurrent
Pension and retirement plans	6,138	14,759
Other	3,987	5,207
Other liabilities, noncurrent, total	$ 10,125	$ 19,966

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental cash flow information
Interest paid	$ 6,375	$ 5,096	$ 4,329
Income taxes paid, net	11,514	10,005	10,578
Noncash transactions
Debt issued for purchases of businesses	(2,402)	(3,099)	(875)
Detail of acquisitions:
Accounts receivable	1,311	1,753	0
Operating supplies	23	0	157
Prepaid expense	89	128	55
Equipment	4,079	1,904	2,485
Other assets	7	52	0
Intangible assets	4,895	4,296	1,374
Goodwill	2,840	5,131	817
Liabilities assumed	2,381	2,713	216
Cash paid	$ 8,461	$ 7,452	$ 3,797

Identified Intangible Assets _3

Identified Intangible Assets and Goodwill, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired finite-lived intangible assets [line Items]
Finite-lived intangible assets, gross	$ 40,170	$ 34,798
Accumulated amortization	30,640	28,604
Intangible assets, net	9,530	6,194
Goodwill	37,971	35,477	$ 30,305
Identified intangible assets and goodwill, net	$ 47,501	41,671
Customer lists/relationships
Acquired finite-lived intangible assets [line Items]
Finite-lived intangible assets, remaining amortization period	3 years 7 months 6 days
Finite-lived intangible assets, gross	$ 25,179	21,487
Accumulated amortization	$ 18,251	16,846
Employment-related
Acquired finite-lived intangible assets [line Items]
Finite-lived intangible assets, remaining amortization period	2 years 9 months 18 days
Finite-lived intangible assets, gross	$ 8,133	7,333
Accumulated amortization	$ 6,954	6,624
Tradenames
Acquired finite-lived intangible assets [line Items]
Finite-lived intangible assets, remaining amortization period	3 years 8 months 12 days
Finite-lived intangible assets, gross	$ 6,858	5,978
Accumulated amortization	$ 5,435	$ 5,134

Identified Intangible Assets _4

Identified Intangible Assets and Goodwill, Net Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, balance at January 1, 2018	$ 35,477	$ 30,305
Goodwill, acquisitions	2,840	5,131	$ 817
Goodwill, translation and other adjustments	(346)	41
Goodwill, balance at December 31, 2018	37,971	35,477	30,305
Utility
Goodwill [Roll Forward]
Goodwill, balance at January 1, 2018	3,424	3,424
Goodwill, acquisitions	1,487	0
Goodwill, translation and other adjustments	0	0
Goodwill, balance at December 31, 2018	4,911	3,424	3,424
Residential and Commercial
Goodwill [Roll Forward]
Goodwill, balance at January 1, 2018	32,053	26,881
Goodwill, acquisitions	1,353	5,131
Goodwill, translation and other adjustments	(346)	41
Goodwill, balance at December 31, 2018	$ 33,060	$ 32,053	$ 26,881

Identified Intangible Assets _5

Identified Intangible Assets and Goodwill, Net (Future Amortization of Intangibles) (Details) $ in Thousands	Dec. 31, 2018USD ($)
Finite-lived intangible assets, net, amortization expense, fiscal year maturity [Abstract]
Year ending December 31, 2019	$ 2,197
2020	2,011
2021	1,569
2022	1,339
2023	1,209
Thereafter	$ 1,205

Short and Long-Term Debt and _3

Short and Long-Term Debt and Commitments Related to Letters of Credit Long-Term Debt (Details) - USD ($) $ in Thousands	Feb. 05, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt instrument [Line Items]
Notes payable		$ 0	$ 149
Short-term debt		22,514	16,315
Revolving credit facility, noncurrent		93,500	100,000
Term loans		23,176	16,242
Long-term debt		178,676	134,242
Less debt issuance costs		599	725
Less current portion		22,514	16,166
Long-term debt, excluding current maturities		155,563	117,351
Swing-line borrowings [Member]
Debt instrument [Line Items]
Revolving credit facility, noncurrent		2,500	0
LIBOR borrowings [Member]
Debt instrument [Line Items]
Revolving credit facility, noncurrent		91,000	100,000
5.09% Senior unsecured notes [Member]
Debt instrument [Line Items]
Senior unsecured notes		12,000	18,000
3.99% Senior unsecured notes [Member]
Debt instrument [Line Items]
Senior unsecured notes		50,000	0
Letter of credit [Member]
Debt instrument [Line Items]
Letters of credit outstanding		72,565	63,242
Letter of credit [Member] | Accounts receivable securitization [Member]
Debt instrument [Line Items]
Letters of credit outstanding		$ 67,438	$ 58,150
Subsequent event [Member] | 3.99% Senior unsecured notes [Member]
Debt instrument [Line Items]
Unsecured debt additional shelf note capacity allowed by credit facility	$ 25,000

Short and Long-Term Debt and _4

Short and Long-Term Debt and Commitments Related to Letters of Credit Narrative (Details)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	May 07, 2017USD ($)
Debt instrument [Line Items]
Committed under credit facility	$ 7,097,000
Revolving credit facility, current borrowing capacity	250,000,000
Revolving credit facility, maximum borrowing capacity	325,000,000
Swing line commitment	$ 25,000,000
Number of principal payments	5
Anniversary when principal payments begin	6
Debt Instrument, Annual Principal Payment	$ 10,000,000
Unused commitments under credit facility	153,377,000
Revolving credit facility, noncurrent	$ 93,500,000	$ 100,000,000
Long-term debt, weighted average interest rate	4.28%	3.56%
Long-term debt, fiscal year maturity [Abstract]
2019	$ 22,514,000
2020	7,569,000
2021	5,093,000
2022	93,500,000
2023	0
thereafter year five	$ 50,000,000
Minimum [Member]
Debt instrument [Line Items]
Line of credit facility, commitment fee percentage	0.10%
Maximum [Member]
Debt instrument [Line Items]
Line of credit facility, commitment fee percentage	0.225%
Line of credit [Member]
Debt instrument [Line Items]
Revolving credit facility, noncurrent	$ 96,623,000
Letter of credit [Member]
Debt instrument [Line Items]
Letters of credit outstanding	$ 72,565,000	$ 63,242,000
London Interbank Offered Rate (LIBOR) [Member] | Line of credit [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	1.50%
London Interbank Offered Rate (LIBOR) [Member] | Line of credit [Member] | Minimum [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	0.875%
London Interbank Offered Rate (LIBOR) [Member] | Line of credit [Member] | Maximum [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	1.50%
Base rate [Member] | Line of credit [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	0.50%
Line of credit [Member] | Letter of credit [Member]
Debt instrument [Line Items]
Letters of credit outstanding	$ 2,004,000	2,004,000
5.09% Senior unsecured notes [Member]
Debt instrument [Line Items]
Senior unsecured notes	$ 12,000,000	18,000,000
Senior unsecured notes, interest rate	5.09%
Debt Instrument, Face Amount	$ 30,000,000
3.99% Senior unsecured notes [Member]
Debt instrument [Line Items]
Senior unsecured notes	$ 50,000,000	0
Senior unsecured notes, interest rate	3.99%
Debt Instrument, Face Amount	$ 50,000,000
Unsecured debt additional shelf note capacity	50,000,000
Unsecured debt maximum borrowing capacity allowed by credit facility	$ 75,000,000
Revolving credit facility [Member] | Minimum [Member]
Debt instrument [Line Items]
Interest coverage ratio	3
Revolving credit facility [Member] | Maximum [Member]
Debt instrument [Line Items]
Ratio of Indebtedness to Net Capital	3
Revolving credit facility [Member] | Letter of credit [Member]
Debt instrument [Line Items]
Letters of credit outstanding	$ 3,123,000	3,088,000
Accounts receivable securitization [Member]
Debt instrument [Line Items]
Senior unsecured notes, interest rate	0.90%
Long-term debt, fiscal year maturity [Abstract]
Unused commitment fee threshold percent	0.50
Debt instrument variable rate base rate calculation, default rate	2.00%
Accounts receivable securitization [Member] | Letter of credit [Member]
Debt instrument [Line Items]
Revolving credit facility, maximum borrowing capacity			$ 100,000,000
Letters of credit outstanding	$ 67,438,000	$ 58,150,000
Long-term debt, fiscal year maturity [Abstract]
Debt instrument, term (in years)	1 year
Accounts receivable securitization [Member] | Letter of credit [Member] | Minimum [Member]
Debt instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.35%
Accounts receivable securitization [Member] | Letter of credit [Member] | Maximum [Member]
Debt instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.45%
Accounts receivable securitization [Member] | Base rate, federal funds [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	0.50%
Line of credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	0.75%
Line of credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt instrument [Line Items]
Outstanding borrowings interest rate margin adjustment range	1.50%
Letter of credit [Member]
Debt instrument [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 100,000,000

Self-Insurance Accruals (Detail

Self-Insurance Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Self-Insurance Accruals [Abstract]
Workers' compensation			$ 41,577	$ 40,764
Present value discount			3,099	2,346
Workers' Compensation, Net of Discount			38,478	38,418
Vehicle liability			13,342	5,536
General liability			31,965	23,740
Total	$ 67,694	$ 62,838	83,785	67,694
Less current portion			27,434	23,782
Noncurrent portion			$ 56,351	$ 43,912
Loss contingency accrual [Roll Forward]
Balance, beginning of year	67,694	62,838
Provision for claims	51,685	34,884
Payment of claims	(35,594)	(30,028)
Balance, end of year	$ 83,785	$ 67,694
Workers' compensation discount rate	2.50%	2.00%

Lease Obligations (Details)

Lease Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capital leased assets [Line Items]
Assets acquired under captial lease, net	$ 4,737	$ 2,676
Capital leases, future minimum payments due, fiscal year maturity [Abstract]
Year ending December 31, 2019	1,426
2020	1,371
2021	1,183
2022	272
2023	71
2024 and after	0
Total minimum lease payments	4,323
Amounts representing interest	116
Present value of net minimum lease payments	4,207
Less current portion	1,345	651
Long-term capital lease obligations, December 31, 2018	2,862	1,859
Operating leases, future minimum payments due, fiscal year maturity [Abstract]
Year ending December 31, 2019	14,023
2020	11,272
2021	7,712
2022	5,129
2023	2,060
2024 and after	1,923
Total minimum lease payments	42,119
Operating leases, rent expense	9,594	7,998	$ 7,536
Equipment [Member]
Capital leased assets [Line Items]
Equipment	6,534	3,481
Less accumulated amortization	$ 1,797	$ 805

Lease Obligations lessee, opera

Lease Obligations lessee, operating lease disclosure (Details)	12 Months Ended
	Dec. 31, 2018
Maximum [Member]
Lessor, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	5 years

Common Shares, Redeemable Com_3

Common Shares, Redeemable Common Shares and Preferred Shares Common shares outstanding (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)shares
Stock split, conversion ratio	2
Preferred shares
Preferred stock, shares authorized	4,000,000
Preferred stock, par value | $ / shares	$ 0
Preferred stock, shares issued	0
Redeemable stock, outstanding	5,642,154	6,467,027	7,056,904
Common stock, number of shares, par value and other disclosures [Abstract]
Common stock, shares authorized	48,000,000	48,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 1	$ 1
Common stock, shares issued	37,271,606	36,446,890	35,856,856
Treasury stock, shares	20,033,108	18,692,901	17,990,620
Common shares, direct sales	17,992
Common shares, value, direct sales | $	$ 345
Stock issued during period, shares, employee benefit plan	395,586
Stock issued during period, value, employee retirement plan | $	$ 7,647
Common shares, employer matching contribution, shares	198,189
Employee retirement plan, employer match | $	$ 3,785
Accrued 401K match | $	$ 4,126
Stock issued during period, shares, employee stock purchase plan	348,973
Increase (decrease) in stockholders' equity [Roll Forward]
Shares outstanding, beginning of year	24,220,859	24,923,140
Shares purchased	(2,636,943)	(1,697,727)
Shares sold	960,740	662,806
Stock subscription offering, employee cash purchases	129,245	90,645
Options exercised	206,751	241,995
Shares outstanding, end of year	22,880,652	24,220,859	24,923,140
Per share amounts and common shares outstanding [Abstract]
Share-based compensation arrangement by share-based payment award, options, exercisable, number	889,814
Stock subscription offering, number of partially-paid subscriptions	690,260
Stock subscription offering, number of rights outstanding	241,236
Treasury stock [Member]
Common stock, number of shares, par value and other disclosures [Abstract]
Shares purchased, value | $	$ 51,116	$ 30,566	$ 25,290
Increase (decrease) in stockholders' equity [Roll Forward]
Shares purchased	(2,637,000)	(1,698,000)	(1,492,000)
Shares sold	961,000	663,000	617,000

Common Shares, Redeemable Com_4

Common Shares, Redeemable Common Shares and Preferred Shares Stock subscription (Details)	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Stock subscription offering [Abstract]
Stock subscription offering, subscription price | $ / shares	$ 9.85
Stock subscription offering, number of shares subscribed | shares	1,275,428
stock subscription offering, value of shares subscribed | $	$ 12,563,000
Stock subscription offering, minimum financed amount | $	$ 5,000
Stock subscription offering, down payment	10.00%
Stock subscription offering, term	7 years
Stock subscription offering interest rate	2.00%
Stock subscription offering, minimum amount to receive right | $	$ 5,000
stock subscription offering, number of shares purchased to receive one right | shares	3
Stock subscription offering, number of rights issued | shares	423,600
Stock subscription offering, portion exercisable per year	14.29%
Stock subscription offering, right expiration term	7 years

Common Shares, Redeemable Com_5

Common Shares, Redeemable Common Shares and Preferred Shares Common shares by class (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Shares, Outstanding	22,880,652	24,220,859	24,923,140
Treasury Stock, Shares, Acquired	(2,636,943)	(1,697,727)
Shares sold	960,740	662,806
Stock subscription offering, employee cash purchases	129,245	90,645
Options exercised	206,751	241,995
Permanent equity [Member]
Class of Stock [Line Items]
Shares, Outstanding	17,238,497	17,753,832	17,866,236
Treasury Stock, Shares, Acquired	(1,530,528)	(807,718)
Shares sold	679,197	362,674
Stock subscription offering, employee cash purchases	129,245	90,645
Options exercised	206,751	241,995
Temporary equity [Member]
Class of Stock [Line Items]
Shares, Outstanding	5,642,155	6,467,027	7,056,904
Treasury Stock, Shares, Acquired	(1,106,415)	(890,009)
Shares sold	281,543	300,132
Stock subscription offering, employee cash purchases	0	0
Options exercised	0	0

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss)	$ (5,034,000)	$ (8,393,000)	$ (12,162,000)	$ (13,394,000)
Unrealized gains (losses)	(2,514,000)	2,195,000	744,000
Amounts reclassified from accumulated other comprehensive income (loss)	6,291,000	4,822,000	2,844,000
Tax effect	(145,000)	(1,962,000)	(1,137,000)
Unrecognized amounts from defined benefit pension plans	(279,000)	(2,169,000)	(2,032,000)
Tax effect	6,000	883,000	813,000
Net of tax amount	3,359,000	3,769,000	1,232,000
Foreign currency translation adjustments [Member]
Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss)	(5,819,000)	(3,305,000)	(5,500,000)	(6,244,000)
Unrealized gains (losses)	(2,514,000)	2,195,000	744,000
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Tax effect	0	0	0
Unrecognized amounts from defined benefit pension plans	0	0	0
Tax effect	0	0	0
Net of tax amount	(2,514,000)	2,195,000	744,000
Defined benefit pension plans [Member]
Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss)	785,000	(5,088,000)	(6,662,000)	$ (7,150,000)
Unrealized gains (losses)	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	6,291,000	4,822,000	2,844,000
Tax effect	(145,000)	(1,962,000)	(1,137,000)
Unrecognized amounts from defined benefit pension plans	(279,000)	(2,169,000)	(2,032,000)
Tax effect	6,000	883,000	813,000
Net of tax amount	$ 5,873,000	$ 1,574,000	$ 488,000

The Davey 401KSOP and Employe_2

The Davey 401KSOP and Employee Stock Ownership Plan (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Employee Stock Ownership Plan (ESOP) disclosures [Line Items]
Employee stock ownership plan (ESOP), initial shares in ESOP | shares	120,000
Employee stock ownership plan (ESOP), shares adjusted for stock splits | shares	23,040,000
Employee stock ownership plan (ESOP), initial value in ESOP	$ 2,700
Defined contribution plan, eligible age	21
Defined contribution plan, service requirement for eligibility (in years)	1 year
Number of put option periods	2
Duration of put option periods (in days)	60 days
Employee Stock Ownership Plan (ESOP), Fair Value of Shares Subject to Repurchase Obligation	$ 6,288	$ 3,843
Company shares held in 401KSOP and ESOP, fair value	112,761	119,677
Redeemable common shares related to 401KSOP and Employee Stock Ownership Plan (ESOP):	119,049	123,520
Employee retirement plan, employer match	$ 4,053	$ 3,794	$ 3,661
First 1% [Member]
Employee Stock Ownership Plan (ESOP) disclosures [Line Items]
Defined contribution plan, employer matching contribution, percent	100.00%
1% to 4% [Member]
Employee Stock Ownership Plan (ESOP) disclosures [Line Items]
Defined contribution plan, employer matching contribution, percent	50.00%
Minimum [Member] | 1% to 4% [Member]
Employee Stock Ownership Plan (ESOP) disclosures [Line Items]
Defined contribution plan, employer matching contribution, percent	1.00%
Maximum [Member] | First 1% [Member]
Employee Stock Ownership Plan (ESOP) disclosures [Line Items]
Defined contribution plan, employer matching contribution, percent	1.00%
Maximum [Member] | 1% to 4% [Member]
Employee Stock Ownership Plan (ESOP) disclosures [Line Items]
Defined contribution plan, employer matching contribution, percent	4.00%

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual percentage of outstanding shares available for grant, maximum	5.00%
Cumulative percentage of outstanding shares available for grant in a year, maximum	10.00%
Salaries, Wages and Officers' Compensation [Abstract]
Compensation expense, stock-based compensation	$ 3,370	$ 4,049	$ 2,811
Income tax benefit	$ 602	$ 1,315	$ 823
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Volatility rate	10.10%	10.30%	10.60%
Risk-free interest rate	2.70%	2.20%	1.80%
Expected dividend yield	0.70%	0.70%	0.70%
Expected life of awards (years)	9 years 2 months 12 days	8 years 10 months 24 days	9 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, ending balance	1,466,264
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercisable, ending balance	889,814
Outstanding, weighted average exercise price, ending balance		$ 13.05
Granted, weighted average exercise price	$ 19.10
Forfeited, weighted average exercise price	$ 13.29
Excess tax benefits	$ 453	$ 691	$ 1,113
Employee stock option [Member]
Salaries, Wages and Officers' Compensation [Abstract]
Compensation expense, stock-based compensation	$ 663	$ 705
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance	1,528,615
Granted	143,250
Exercised	(147,321)
Forfeited	58,280
Outstanding, ending balance		1,528,615
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, weighted average exercise price, ending balance	$ 13.94
Exercised, weighted average exercise price	9.93
Exercisable, weighted average exercise price	$ 11.79
Outstanding, weighted average remaining contractual life (years)	5 years 10 months 10 days
Exercisable, weighted average remaining contractual life (years)	4 years 7 months 28 days
Unrecognized compensation cost	$ 1,393
Outstanding, aggregate intrinsic value	8,446
Exercisable, aggregate intrinisic value	$ 7,037
Number outstanding	1,466,264
Outstanding options, weighted average exercise price	$ 13.94
Number exercisable	889,814
Exercisable options, weighted average exercise price	$ 11.79
Employee stock option [Member] | $8.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	8
Upper range limit	$ 8
Number outstanding	88,413
Weighted average remaining contractual life (years)	10 months 2 days
Outstanding options, weighted average exercise price	$ 8
Number exercisable	88,413
Exercisable options, weighted average exercise price	$ 8
Employee stock option [Member] | $8.30 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	8.3
Upper range limit	$ 8.3
Number outstanding	107,000
Weighted average remaining contractual life (years)	1 year 10 months 2 days
Outstanding options, weighted average exercise price	$ 8.30
Number exercisable	107,000
Exercisable options, weighted average exercise price	$ 8.30
Employee stock option [Member] | $11.60 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	11.6
Upper range limit	$ 11.6
Number outstanding	270,414
Weighted average remaining contractual life (years)	4 years 5 months 23 days
Outstanding options, weighted average exercise price	$ 11.60
Number exercisable	270,414
Exercisable options, weighted average exercise price	$ 11.60
Employee stock option [Member] | $13.20 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	13.2
Upper range limit	$ 13.2
Number outstanding	284,822
Weighted average remaining contractual life (years)	5 years 6 months
Outstanding options, weighted average exercise price	$ 13.20
Number exercisable	211,422
Exercisable options, weighted average exercise price	$ 13.20
Employee stock option [Member] | $15.05 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	15.05
Upper range limit	$ 15.05
Number outstanding	219,965
Weighted average remaining contractual life (years)	6 years 6 months
Outstanding options, weighted average exercise price	$ 15.05
Number exercisable	112,765
Exercisable options, weighted average exercise price	$ 15.05
Employee stock option [Member] | $16.35 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	16.35
Upper range limit	$ 16.35
Number outstanding	230,800
Weighted average remaining contractual life (years)	7 years 6 months
Outstanding options, weighted average exercise price	$ 16.35
Number exercisable	77,800
Exercisable options, weighted average exercise price	$ 16.35
Employee stock option [Member] | $17.60 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	17.60
Upper range limit	$ 17.60
Number outstanding	129,300
Weighted average remaining contractual life (years)	8 years 5 months 23 days
Outstanding options, weighted average exercise price	$ 17.60
Number exercisable	22,000
Exercisable options, weighted average exercise price	$ 17.60
Employee stock option [Member] | $19.10 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Lower range limit	19.10
Upper range limit	$ 19.10
Number outstanding	135,550
Weighted average remaining contractual life (years)	9 years 6 months
Outstanding options, weighted average exercise price	$ 19.10
Number exercisable	0
Exercisable options, weighted average exercise price	$ 19.10
Equity option [Member]
Salaries, Wages and Officers' Compensation [Abstract]
Compensation expense, stock-based compensation			596
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Vesting period	10 years
Stock Appreciation Rights (SARs) [Member]
Salaries, Wages and Officers' Compensation [Abstract]
Compensation expense, stock-based compensation	$ 540	$ 1,035	591
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Vesting period	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested, beginning balance	448,180
Granted	121,243
Forfeited	0
Vested	(188,441)
Unvested, ending balance	380,982	448,180
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Unvested, weighted average award date value, beginning balance	$ 3.10
Granted, weighted average award date value	3.84
Forfeited, weighted average award date value	0
Vested, weighted average award date value	2.93
Unvested, weighted average award date value, ending balance	$ 3.42	$ 3.10
Weighted average remaining contractual life (years)	2 years 4 months 24 days
Unrecognized compensation cost	$ 924
Aggregate intrinsic value, unvested	7,505
Restricted Stock Units (RSUs) [Member]
Salaries, Wages and Officers' Compensation [Abstract]
Compensation expense, stock-based compensation	$ 1,169	$ 1,421	897
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested, beginning balance	290,666
Granted	44,926
Forfeited	0
Vested	(87,754)
Unvested, ending balance	247,838	290,666
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Unvested, weighted average award date value, beginning balance	$ 14.41
Granted, weighted average award date value	18.55
Forfeited, weighted average award date value	0
Vested, weighted average award date value	12.94
Unvested, weighted average award date value, ending balance	$ 15.68	$ 14.41
Weighted average remaining contractual life (years)	1 year 10 months 24 days
Unrecognized compensation cost	$ 1,727
Aggregate intrinsic value, unvested	$ 4,882
Employee PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted	31,738
Unvested, ending balance	209,186
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Unvested, weighted average award date value, ending balance	$ 15.40
Weighted average remaining contractual life (years)	2 years 2 months 12 days
Unrecognized compensation cost	$ 1,401
Aggregate intrinsic value, unvested	$ 4,121
Nonemployee Director RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted	13,188
Unvested, ending balance	38,652
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Unvested, weighted average award date value, ending balance	$ 17.17
Weighted average remaining contractual life (years)	1 year 3 months 18 days
Unrecognized compensation cost	$ 326
Aggregate intrinsic value, unvested	761
The Davey Employee Stock Purchase Plan [Member]
Salaries, Wages and Officers' Compensation [Abstract]
Compensation expense, stock-based compensation	$ 998	$ 888	$ 727
Employee Stock Purchase Plan [Abstract]
Employee stock purchase plan, service period (in years)	1 year
Employee stock purchase plan, percentage of market price, purchase date	85.00%
Employee stock purchase, discount from market price, purchase date	15.00%

Defined Benefit Pension Plans C

Defined Benefit Pension Plans Change in benefit obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined benefit plan, change in benefit obligation [Roll Forward]
Projected benefit obligation at beginning of year	$ 19,403	$ 24,833
Service cost	400	530	$ 370
Interest cost	718	1,002	1,243
Actuarial (gains)/losses	(77)	1,865
Amendments	0	0
Settlements	(13,118)	(8,400)
Benefits paid	(262)	(427)
Projected benefit obligation at end of year	7,064	19,403	$ 24,833
Accumulated benefit obligation at end of year	$ 7,064	$ 19,403

Defined Benefit Pension Plans_2

Defined Benefit Pension Plans Change in fair value of plan assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Defined benefit plan, change in fair value of plan assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 7,105	$ 11,509
Actual return on plan assets	239	845
Plan expenses, including PBGC premiums	(364)	(513)
Employer contributions	10,158	4,091
Settlements	(13,118)	(8,400)
Fair value of plan assets at end of year	3,758	7,105
Defined Benefit Plan, Plan Assets, Benefits Paid	$ (262)	$ (427)
Employee retirement plan [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, number of employees settled	905

Defined Benefit Pension Plans F

Defined Benefit Pension Plans Funded status of the plans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	$ 3,758	$ 7,105	$ 11,509
Projected benefit obligation	7,064	19,403	$ 24,833
Funded status of the plans	(3,306)	(12,298)
Defined Benefit Plan, Plan Name ERP Funded Status	(332)	(9,084)
Defined Benefit Plan, Plan Name SERP Funded Status	(2,564)	(2,759)
Defined Benefit Plan, Plan Name Restoration Plan Funded Status	$ (410)	$ (455)

Defined Benefit Pension Plans A

Defined Benefit Pension Plans Amounts reported in the consolidated balance sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined benefit plan disclosure [Line Items]
Current liability	$ (187)	$ (175)
Noncurrent liability	(3,119)	(12,123)
Funded status of the plans	$ (3,306)	$ (12,298)

Defined Benefit Pension Plans_3

Defined Benefit Pension Plans Amounts reported in accumulated other comprehensive income (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amounts reported in accumulated other comprehensive income
Unrecognized net actuarial loss, pretax	$ 2,139	$ 8,086
Unrecognized net actuarial loss, net of tax	(714)	4,919
Unrecognized prior service cost, pretax	214	278
Unrecognized prior service cost, net of tax	(71)	169
Amounts reported in accumulated other comprehensive income, pretax	2,353	8,364
Amounts reported in accumulated other comprehensive income, net of tax	(785)	5,088
Amortization of Costs Expected to be Recognized Next Year
Unrecognized net actuarial loss, pretax	175
Unrecognized net actuarial loss, net of tax	131
Unrecognized prior service cost, pretax	64
Unrecognized prior service cost, net of tax	48
Amortization of costs expected to be recognized next year, pretax	239
Amortization of costs expected to be recognized next year, net of tax	179
For pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	7,064	19,403	$ 24,833
Accumulated benefit obligation	7,064	19,403
Fair value of plan assets	$ 3,758	$ 7,105	$ 11,509

Defined Benefit Pension Plans_4

Defined Benefit Pension Plans Actuarial Assumptions (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined benefit plan disclosure [Line Items]
Discount rate	4.35%	3.70%	4.20%
Expected long-term rate of return on plan assets	2.50%	2.50%	5.00%
Fixed income and cash [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		100.00%
Fixed Income Investments [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		5.00%
Minimum [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, risk management practices, investment evaluation period	3 years
Minimum [Member] | Equity securities [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		20.00%
Minimum [Member] | Fixed income and cash [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		50.00%
Minimum [Member] | Alternative investments [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		0.00%
Maximum [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, risk management practices, investment evaluation period	5 years
Maximum [Member] | Equity securities [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		40.00%
Maximum [Member] | Fixed income and cash [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		70.00%
Maximum [Member] | Alternative investments [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, target plan asset allocations		15.00%

Defined Benefit Pension Plans_5

Defined Benefit Pension Plans Components of Pension Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs--increase in benefit obligation earned	$ 400	$ 530	$ 370
Interest cost on projected benefit obligation	718	1,002	1,243
Expected return on plan assets	(231)	(638)	(1,044)
Curtailment loss	0	0	0
Settlement loss	5,499	3,849	2,346
Amortization of net actuarial loss	728	909	951
Amortization of prior service cost	64	64	0
Net pension expense of defined benefit pension plans	$ 7,178	$ 5,716	$ 3,866

Defined Benefit Pension Plans_6

Defined Benefit Pension Plans Fair Value of Plan Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Defined benefit plan disclosure [Line Items]
Total carrying value	$ 3,758	$ 7,105
Fair value of plan assets	3,758	7,105	$ 11,509
Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	6,208
Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	3,758	897
Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Money market funds
Defined benefit plan disclosure [Line Items]
Total carrying value	3,758	897
Money market funds | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		0
Money market funds | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	3,758	897
Money market funds | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, growth [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	576
U.S. large-cap equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		576
U.S. large-cap equities, growth [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, growth [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, value [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	542
U.S. large-cap equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		542
U.S. large-cap equities, value [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, value [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, growth [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	246
U.S. small/mid-cap equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		246
U.S. small/mid-cap equities, growth [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, growth [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, value [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	247
U.S. small/mid-cap equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		247
U.S. small/mid-cap equities, value [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, value [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, growth [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	376
International equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		376
International equities, growth [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, growth [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, value [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	366
International equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		366
International equities, value [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, value [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Fixed income
Defined benefit plan disclosure [Line Items]
Total carrying value	0	3,070
Fixed income | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		3,070
Fixed income | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Fixed income | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Multiclass world-allocation mutual funds
Defined benefit plan disclosure [Line Items]
Total carrying value	0	785
Multiclass world-allocation mutual funds | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		785
Multiclass world-allocation mutual funds | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Multiclass world-allocation mutual funds | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Employee retirement plan [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, number of employees settled	905

Defined Benefit Pension Plans E

Defined Benefit Pension Plans Expected Benefits (Details) $ in Thousands	Dec. 31, 2018USD ($)
Defined benefit plan disclosure [Line Items]
Year ending December 31, 2019	$ 356
2020	379
2021	384
2022	386
2023	389
Years 2024 to 2028	1,986
Pension plans, defined benefit [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plans, estimated future employer contributions in next fiscal year	$ 191

Defined Benefit Pension Plans M

Defined Benefit Pension Plans Multiemployer Pension Plans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Multiemployer Plans [Line Items]
Multiemployer plan, period contributions	$ 910	$ 887	$ 802
National Electric Benefit Fund [Member]
Multiemployer Plans [Line Items]
Number of collective-bargaining agreements	10
Multiemployer plan, period contributions	$ 768	785	712
Eighth District Electrical Pension Fund [Member]
Multiemployer Plans [Line Items]
Number of collective-bargaining agreements	1
Multiemployer plan, period contributions	$ 142	$ 102	$ 90

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Remeasurement of deferred tax assets and liabilities		$ 1,000
Income tax liability, transition toll tax					$ 6,100
Income before income taxes
Income before income taxes	$ 37,496	37,994	$ 37,244
Provision for income taxes
Federal	3,165	9,914	12,216
State	2,290	2,469	2,286
Canadian	50	(262)	398
Total current	5,505	12,121	14,900
Deferred taxes	4,014	3,753	60
Total taxes on income	$ 9,519	$ 15,874	$ 14,960
Tax rate reconciliation
Statutory U.S. federal tax rate	21.00%	35.00%	35.00%
State income taxes, net of federal benefit	5.70%	4.90%	4.00%
Effect of Canadian income taxes	0.10%	0.30%	(0.20%)
Nondeductible expenses	2.10%	2.20%	2.20%
ESOP dividend deduction	(0.30%)	(0.60%)	(0.70%)
Uncertain tax adjustments and audit settlement	(3.80%)	(0.20%)	0.20%
Income tax reform - deferred rate remeasurement	0.00%	2.50%	0.00%
All other, net	0.60%	(2.30%)	(0.30%)
Effective income tax rate	25.40%	41.80%	40.20%
Noncurrent deferred tax assets and liabilities, net
Self-insurance accruals				$ 17,579	14,186
Accrued compensated absences				1,565	1,747
Accrued expenses and other liabilities				742	798
Accrued stock compensation				1,772	1,571
Defined benefit pension plans				442	2,289
Foreign tax credit carryforward				2,117	605
Other future deductible amounts, net				3,271	3,661
Deferred tax assets, gross,noncurrent				27,488	24,857
Less deferred tax asset valuation allowance				1,683	0
Deferred tax assets, net--noncurrent				25,805	24,857
Intangibles				1,178	969
Prepaid expenses				3,160	2,300
Property and equipment				20,894	16,773
Deferred Tax Liabilities, Gross, Noncurrent				25,232	20,042
Net deferred tax assets--noncurrent				573	4,815
Undistributed earnings of foreign subsidiaries				28,856
Unrecognized benefits and related interest and penalties
Unrecognized tax benefits	$ 2,581	$ 2,532	$ 2,557	1,325	2,581
Portion, if recognized, would reduce tax expense and effective tax rate				599	1,948
Accrued interest on unrecognized tax benefits				$ 35	$ 128
Reconciliation of unrecognized tax benefits
Balance, beginning of year	2,581	2,532	2,557
Additions based on tax positions related to the current year	224	650	402
Additions for tax positions of prior years	20	0	51
Reductions for tax positions of prior years	(1,500)	(21)	(39)
Lapses in statutes of limitations	0	(580)	(439)
Balance, end of year	1,325	2,581	2,532
United States
Income before income taxes
Income before income taxes	37,377	38,800	35,867
Canada
Income before income taxes
Income before income taxes	$ 119	$ (806)	$ 1,377

Earnings Per Share Informatio_2

Earnings Per Share Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income	$ 4,506	$ 8,384	$ 21,714	$ (6,627)	$ 1,547	$ 10,237	$ 14,223	$ (3,887)	$ 27,977	$ 22,120	$ 22,284
Weighted-average shares, basic
Outstanding									23,698,478	24,793,086	25,378,600
Partially-paid share subscriptions									690,260	764,382	833,440
Basic weighted-average shares									24,388,738	25,557,468	26,212,040
Weighted-average shares, diluted
Exercise of stock subscription purchase rights									141,287	146,453	142,746
Exercise of stock options and awards									950,593	993,141	892,568
Diluted weighted-average shares									25,480,618	26,697,062	27,247,354
Earnings per share--basic	$ 0.12	$ 0.35	$ 0.94	$ (0.26)	$ 0.04	$ 0.41	$ 0.57	$ (0.15)	$ 1.15	$ 0.87	$ 0.85
Earnings per share--diluted	$ 0.13	$ 0.34	$ 0.89	$ (0.26)	$ 0.04	$ 0.39	$ 0.55	$ (0.15)	$ 1.10	$ 0.83	$ 0.82

Operations by Business Segmen_3

Operations by Business Segment and Geographic Information Operations by Busines Segment (Details) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018USD ($)	Sep. 29, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jul. 01, 2017USD ($)	Apr. 01, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments										2
Revenues										$ 1,024,791	$ 915,958	$ 845,678
Income (loss) from operations		$ 16,971	$ 14,585	$ 29,800	$ (5,666)	$ 11,478	$ 19,049	$ 25,659	$ (3,995)	55,690	52,191	48,867
Interest expense										7,039	4,886	4,393
Interest income										350	292	255
Other										(11,505)	(9,603)	(7,485)
Income before income taxes										37,496	37,994	37,244
Depreciation										54,914	50,702	47,284
Amortization										2,055	2,384	2,306
Capital expenditures										60,410	57,100	56,646
Segment assets, total		526,623				473,135				526,623	473,135	423,939
Utility Services
Segment Reporting Information [Line Items]
Revenues										537,484	466,727	433,379
Income (loss) from operations										32,370	18,223	19,256
Depreciation										29,526	27,928	26,855
Amortization										211	122	135
Capital expenditures										32,148	26,910	28,660
Segment assets, total		239,426				189,662				239,426	189,662	171,220
Residential Commercial Services
Segment Reporting Information [Line Items]
Revenues										486,005	446,028	410,878
Income (loss) from operations										47,812	41,158	36,640
Depreciation										21,720	19,384	17,198
Amortization										1,842	2,240	2,136
Capital expenditures										22,256	23,199	21,819
Segment assets, total		208,369				197,698				208,369	197,698	166,858
All Other
Segment Reporting Information [Line Items]
Revenues										1,302	3,203	1,421
Income (loss) from operations										(19,816)	(2,634)	(4,318)
Depreciation										0	0	0
Amortization										0	0	0
Capital expenditures										0	0	0
Segment assets, total		0				0				0	0	0
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenues										0	0	0
Income (loss) from operations	[1]									(4,676)	(4,556)	(2,711)
Interest expense										7,039	4,886	4,393
Interest income										350	292	255
Other										(11,505)	(9,603)	(7,485)
Depreciation	[2]									3,668	3,390	3,231
Amortization										2	22	35
Capital expenditures										6,006	6,991	6,167
Segment assets, total	[3]	$ 78,828				$ 85,775				$ 78,828	$ 85,775	$ 85,861
[1]	Reconciling adjustments from segment reporting to consolidated external financial reporting include reclassification of depreciation expense and allocation of corporate expenses.
[2]	Adjustments to declining-balance method depreciation expense from straight-line method and depreciation and amortization of corporate assets.
[3]	Corporate assets include cash, prepaid expenses, corporate facilities, enterprise-wide information systems and other nonoperating assets.

Operations by Business Segmen_4

Operations by Business Segment and Geographic Information Geographic Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 1,024,791	$ 915,958	$ 845,678
Long-lived assets, net	271,555	264,011	245,166
United States
Segment Reporting Information [Line Items]
Revenues	949,317	847,540	775,870
Long-lived assets, net	251,181	242,118	224,727
Canada
Segment Reporting Information [Line Items]
Revenues	75,474	68,418	69,808
Long-lived assets, net	$ 20,374	$ 21,893	$ 20,439

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	$ 1,024,791
Contract with customer, asset and liability [Abstract]
Revenue recognized	1,443
Contract liabilities - current	2,907	$ 2,072
Contract liabilities - noncurrent	2,287	2,020
Net contract liabilities	5,194	$ 4,092
Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	537,484
Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	486,005
All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	1,302
United States
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	949,317
United States | Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	499,242
United States | Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	448,773
United States | All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	1,302
Canada
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	75,474
Canada | Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	38,242
Canada | Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	37,232
Canada | All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	0
Tree and plant care
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	683,901
Tree and plant care | Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	394,481
Tree and plant care | Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	290,940
Tree and plant care | All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	(1,520)
Grounds maintenance
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	117,498
Grounds maintenance | Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	0
Grounds maintenance | Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	117,498
Grounds maintenance | All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	0
Storm damage services
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	23,311
Storm damage services | Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	13,864
Storm damage services | Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	9,447
Storm damage services | All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	0
Consulting and other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	200,081
Consulting and other | Utility
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	129,139
Consulting and other | Residential and Commercial
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	68,120
Consulting and other | All Other
Disaggregation of revenue [Line Items]
Revenue from contracts with customers	$ 2,822

Fair Value Measurements and F_3

Fair Value Measurements and Financial Instruments Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Defined benefit pension plan assets	$ 3,758	$ 7,105	$ 11,509
Revolving credit facility, noncurrent	93,500	100,000
Total	155,563	117,351
Quoted prices in active markets, (level 1) [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Defined benefit pension plan assets	0	6,208
Significant other observable inputs, (level 2) [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Defined benefit pension plan assets	3,758	897
Significant unobservable inputs (level 3) [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Defined benefit pension plan assets	0	0
Fair value measurements, recurring [Member] | Quoted prices in active markets, (level 1) [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	15,379	19,422
Defined benefit pension plan assets	0	6,208
Deferred compensation	0	0
Fair value measurements, recurring [Member] | Significant other observable inputs, (level 2) [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	0	0
Defined benefit pension plan assets	3,758	897
Deferred compensation	2,459	2,146
Fair value measurements, recurring [Member] | Significant unobservable inputs (level 3) [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	0	0
Defined benefit pension plan assets	0	0
Deferred compensation	0	0
Fair value [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Revolving credit facility, noncurrent	93,500	100,000
Senior unsecured notes	56,002	12,389
Term loans, noncurrent	6,868	10,038
Total	156,370	122,427
Total carrying value [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Revolving credit facility, noncurrent	93,500	100,000
Senior unsecured notes	56,000	12,000
Term loans, noncurrent	6,662	7,935
Total	156,162	119,935
Total carrying value [Member] | Fair value measurements, recurring [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets invested for self-insurance, classified as other assets, noncurrent	15,379	19,422
Defined benefit pension plan assets	3,758	7,105
Deferred compensation	$ 2,459	$ 2,146

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Loss contingency number of claims alleged	3
Letter of credit [Member]
Letters of credit outstanding	$ 72,565	$ 63,242
Former Davey employee defendants [Member]
Loss contingency, number of defendants	1
Employee and former employee defendants [Member]
Loss contingency, number of defendants	4
Former Wolf employee defendants [Member]
Loss contingency, number of defendants	1
Former Wolf employee defendants indicted [Member]
Loss contingency, number of defendants	2
Other individuals [Member]
Loss contingency, number of defendants	1

Quarterly Results of Operatio_3

Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 280,173	$ 265,318	$ 270,649	$ 208,651	$ 228,520	$ 249,588	$ 245,037	$ 192,813	$ 1,024,791	$ 915,958	$ 845,678
Gross profit (revenues less costs and expenses, operating)	98,215	94,193	102,967	64,028	83,986	91,973	93,512	59,154
Income (loss) from operations	16,971	14,585	29,800	(5,666)	11,478	19,049	25,659	(3,995)	55,690	52,191	48,867
Net income (loss)	$ 4,506	$ 8,384	$ 21,714	$ (6,627)	$ 1,547	$ 10,237	$ 14,223	$ (3,887)	$ 27,977	$ 22,120	$ 22,284
Net income (loss) per share -- Basic	$ 0.12	$ 0.35	$ 0.94	$ (0.26)	$ 0.04	$ 0.41	$ 0.57	$ (0.15)	$ 1.15	$ 0.87	$ 0.85
Net income (loss) per share -- Diluted	0.13	0.34	0.89	(0.26)	0.04	0.39	0.55	(0.15)	$ 1.10	$ 0.83	$ 0.82
ESOT valuation per share	$ 21.10	$ 19.70	$ 19.70	$ 19.10	$ 19.10	$ 18.30	$ 18.30	$ 17.60
Decrease in casualty insurance expense	$ (7,324)				$ 2,735

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Customer concentration risk [Member]
Concentration risk [Line Items]
Pre-petition accounts receivable balance	$ 13,000
Credit concentration risk [Member]
Concentration risk [Line Items]
Percent of sales	12.00%	11.00%	12.00%

Subsequent Events Business comb

Subsequent Events Business combination (Details) $ in Thousands	2 Months Ended	12 Months Ended
	Mar. 11, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business acquisition [Line Items]
Number of Businesses Acquired	2
Consideration transferred		$ 8,461	$ 7,452	$ 3,797
Liabilities assumed		2,381	2,713	216
Debt issued		$ 2,402	$ 3,099	$ 875
Subsequent event [Member]
Business acquisition [Line Items]
Consideration transferred	$ 3,950
Liabilities assumed	0
Debt issued	$ 1,092

Subsequent Events Debt issuance

Subsequent Events Debt issuance (Details) $ in Thousands	Feb. 05, 2019USD ($)	Dec. 31, 2018USD ($)
Debt instrument [Line Items]
Number of principal payments		5
Anniversary when principal payments begin		6
3.99% Senior unsecured notes [Member]
Debt instrument [Line Items]
Senior unsecured notes, interest rate		3.99%
Unsecured debt additional shelf note capacity		$ 50,000
Subsequent event [Member]
Debt instrument [Line Items]
Number of principal payments	5
Subsequent event [Member] | 4.00% Senior unsecured notes [Member]
Debt instrument [Line Items]
Senior unsecured notes, interest rate	4.00%
Unsecured debt additional shelf note capacity	$ 25,000
Subsequent event [Member] | 3.99% Senior unsecured notes [Member]
Debt instrument [Line Items]
Unsecured debt additional shelf note capacity allowed by credit facility	$ 25,000