Old Dominion Freight Line (ODFL) 10-K 24 Feb 21 2020 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	ODFL
Entity Registrant Name	OLD DOMINION FREIGHT LINE, INC.
Entity Central Index Key	0000878927
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		116,937,111
Entity Public Float			$ 16,302,404,841
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
ICFR Auditor Attestation Flag	true
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock ($0.10 par value)
Security Exchange Name	NASDAQ
Entity File Number	0-19582
Entity Incorporation, State or Country Code	VA
Entity Tax Identification Number	56-0751714
Entity Address, Address Line One	500 Old Dominion Way
Entity Address, City or Town	Thomasville
Entity Address, State or Province	NC
Entity Address, Postal Zip Code	27360
City Area Code	336
Local Phone Number	889-5000
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Certain portions of the Company’s Proxy Statement for the 2021 Annual Meeting of Shareholders are incorporated by reference into Part III of this report.

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 30, 2019
Current assets:
Cash and cash equivalents	$ 401,430	$ 403,571
Short-term investments	330,274
Customer receivables, less allowances of $8,979 and $8,866, respectively	444,653	397,579
Other receivables	9,569	10,586
Prepaid expenses and other current assets	57,413	55,098
Total current assets	1,243,339	866,834
Property and equipment:
Revenue equipment	1,885,649	1,898,999
Land and structures	2,218,290	2,039,937
Other fixed assets	475,264	482,425
Leasehold improvements	12,226	11,709
Total property and equipment	4,591,429	4,433,070
Less: Accumulated depreciation	(1,677,398)	(1,464,235)
Net property and equipment	2,914,031	2,968,835
Other assets	212,040	159,899
Total assets	4,369,410	3,995,568
Current liabilities:
Accounts payable	68,511	70,254
Compensation and benefits	191,303	192,524
Claims and insurance accruals	53,092	54,330
Other accrued liabilities	51,513	46,130
Income taxes payable	8,711	2,847
Total current liabilities	373,130	366,085
Long-term debt	99,931	45,000
Other non-current liabilities	349,851	241,802
Deferred income taxes	220,210	261,964
Total long-term liabilities	669,992	548,766
Total liabilities	1,043,122	914,851
Commitments and contingent liabilities
Shareholders’ equity
Common stock - $0.10 par value, 280,000,000 shares authorized, 117,057,696 shares outstanding at December 31, 2020 and 140,000,000 shares authorized, 119,532,534 shares outstanding at December 31, 2019	11,706	11,953
Capital in excess of par value	226,451	218,462
Retained earnings	3,088,131	2,850,302
Total shareholders’ equity	3,326,288	3,080,717
Total liabilities and shareholders’ equity	$ 4,369,410	$ 3,995,568

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Customer receivables, allowances	$ 8,979	$ 8,866
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	280,000,000	140,000,000
Common stock, shares outstanding	117,057,696	119,532,534

Statements of Operations

Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue from operations	$ 4,015,129	$ 4,109,111	$ 4,043,695
Operating expenses:
Salaries, wages and benefits	2,053,894	2,122,464	2,075,602
Operating supplies and expenses	373,431	473,114	497,476
General supplies and expenses	110,279	123,975	119,180
Operating taxes and licenses	116,943	116,839	112,210
Insurance and claims	42,364	52,549	44,118
Communications and utilities	31,542	29,601	31,070
Depreciation and amortization	261,259	253,681	230,357
Purchased transportation	97,947	89,636	96,017
Miscellaneous expenses, net	20,588	28,546	20,614
Total operating expenses	3,108,247	3,290,405	3,226,644
Operating income	906,882	818,706	817,051
Non-operating expense (income):
Interest expense	2,782	377	189
Interest income	(1,830)	(6,763)	(3,113)
Other expense, net	4,566	1,143	4,462
Total non-operating expense (income)	5,518	(5,243)	1,538
Income before income taxes	901,364	823,949	815,513
Provision for income taxes	228,682	208,431	209,845
Net income	$ 672,682	$ 615,518	$ 605,668
Earnings per share:
Basic	$ 5.71	$ 5.11	$ 4.93
Diluted	$ 5.68	$ 5.10	$ 4.92
Weighted average shares outstanding:
Basic	117,737,180	120,414,218	122,885,346
Diluted	118,493,203	120,609,599	123,029,672
Dividends declared per share	$ 0.60	$ 0.45	$ 0.35

Statements of Changes in Shareh

Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2017	$ 2,276,854	$ 12,356	$ 134,395	$ 2,130,103
Balance, in shares at Dec. 31, 2017		123,564
Net income	605,668			605,668
Share repurchases	(163,265)	$ (176)		(163,089)
Share repurchases, shares		(1,763)
Cash dividends declared	(42,594)			(42,594)
Share-based compensation and restricted share issuances, net of forfeitures	4,894	$ 6
Share-based compensation and restricted share issuances, net of forfeitures, shares		58
Share-based compensation and restricted share issuances, net of forfeitures			4,888
Taxes paid in exchange for shares withheld	(1,074)	$ (1)	(1,073)
Taxes paid in exchange for shares withheld, shares		(12)
Balance at Dec. 31, 2018	2,680,483	$ 12,185	138,210	2,530,088
Balance, in shares at Dec. 31, 2018		121,847
Net income	615,518			615,518
Share repurchases	(240,960)	$ (240)		(240,720)
Share repurchases, shares		(2,403)
Cash dividends declared	(54,584)			(54,584)
Reclassification of liability for modified equity awards	64,991		64,991
Share-based compensation and restricted share issuances, net of forfeitures	16,717	$ 10
Share-based compensation and restricted share issuances, net of forfeitures, shares		104
Share-based compensation and restricted share issuances, net of forfeitures			16,707
Taxes paid in exchange for shares withheld	(1,448)	$ (2)	(1,446)
Taxes paid in exchange for shares withheld, shares		(15)
Balance at Dec. 31, 2019	3,080,717	$ 11,953	218,462	2,850,302
Balance, in shares at Dec. 31, 2019		119,533
Net income	672,682			672,682
Share repurchases	(364,057)	$ (250)		(363,807)
Share repurchases, shares		(2,508)
Cash dividends declared	(71,046)			(71,046)
Cash paid for fractional shares	(612)	$ (1)	(611)
Cash paid for fractional shares, shares		(5)
Share-based compensation and restricted share issuances, net of forfeitures	11,337	$ 6
Share-based compensation and restricted share issuances, net of forfeitures, shares		57
Share-based compensation and restricted share issuances, net of forfeitures			11,331
Taxes paid in exchange for shares withheld	(2,733)	$ (2)	(2,731)
Taxes paid in exchange for shares withheld, shares		(19)
Balance at Dec. 31, 2020	$ 3,326,288	$ 11,706	$ 226,451	$ 3,088,131
Balance, in shares at Dec. 31, 2020		117,058

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 672,682	$ 615,518	$ 605,668
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	261,267	253,681	230,357
Noncash lease expense	11,963	11,066
Loss on disposal of property and equipment	736	6,066	477
Deferred income taxes	(41,011)	13,157	57,709
Share-based compensation	11,337	16,717	4,894
Changes in assets and liabilities:
Customer and other receivables, net	(49,045)	30,330	(34,666)
Prepaid expenses and other assets	(1,722)	(16,807)	(12,003)
Accounts payable	(1,743)	(8,264)	4,789
Compensation, benefits and other accrued liabilities	72,928	3,263	47,552
Claims and insurance accruals	(1,459)	5,297	8,142
Income taxes, net	8,750	32,612	(17,813)
Other liabilities	(11,659)	21,252	5,010
Net cash provided by operating activities	933,024	983,888	900,116
Cash flows from investing activities:
Purchase of property and equipment	(225,081)	(479,325)	(588,292)
Proceeds from sale of property and equipment	3,690	5,686	6,983
Purchase of short-term investments	(360,160)
Proceeds from maturities of short-term investments	29,988
Other investing activities, net	(100)		918
Net cash used in investing activities	(551,663)	(473,639)	(580,391)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	99,923
Principal payments under debt agreements	(45,000)		(50,000)
Dividends paid	(71,023)	(54,552)	(42,566)
Payments for share repurchases	(364,057)	(240,960)	(163,265)
Other financing activities, net	(3,345)	(1,448)	(1,074)
Net cash used in financing activities	(383,502)	(296,960)	(256,905)
(Decrease) increase in cash and cash equivalents	(2,141)	213,289	62,820
Cash and cash equivalents at beginning of year	403,571	190,282	127,462
Cash and cash equivalents at end of year	401,430	403,571	190,282
Income taxes paid	266,506	157,290	170,035
Interest paid	5,686	3,857	4,525
Capitalized interest	$ 2,473	$ 3,128	$ 3,237

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Significant Accounting Policies	Note 1. Significant Accounting Policies Business We are one of the largest North American less-than-truckload (“LTL”) motor carriers. We provide regional, inter-regional and national LTL services through a single integrated, union-free organization. Our service offerings, which include expedited transportation, are provided through an expansive network of service centers located throughout the continental United States. Through strategic alliances, we also provide LTL services throughout North America. In addition to our core LTL services, we offer a range of value-added services including container drayage, truckload brokerage and supply chain consulting. We have one operating segment and no single customer exceeds 5% of our revenue. The composition of our revenue is summarized below: Year Ended December 31, (In thousands) 2020 2019 2018 LTL services $ 3,961,054 $ 4,055,467 $ 3,982,658 Other services 54,075 53,644 61,037 Total revenue $ 4,015,129 $ 4,109,111 $ 4,043,695 Basis of Presentation The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Certain amounts in prior years have been reclassified to conform prior years’ financial statements to the current presentation. Unless the context requires otherwise, references in these Notes to “Old Dominion,” the “Company,” “we,” “us” and “our” refer to Old Dominion Freight Line, Inc. Revenue and Expense Recognition We recognize revenue based upon when our transportation and related services have been completed in accordance with the bill of lading (“BOL”) contract, our general tariff provisions and contractual agreements with our customers. Generally, our performance obligations begin when we receive a BOL from a customer and are satisfied when we complete the delivery of a shipment and related services. We recognize revenue for our performance obligations under our customer contracts over time, as our customers receive the benefits of our services in accordance with Accounting Standards Update (“ASU”) 2014-09. With respect to services not completed at the end of a reporting period, we use a percentage of completion method to allocate the appropriate revenue to each separate reporting period. Under this method, we develop a factor for each uncompleted shipment by dividing the actual number of days in transit at the end of a reporting period by that shipment’s standard delivery time schedule. This factor is applied to the total revenue for that shipment and revenue is allocated between reporting periods accordingly. Payment terms vary by customer and are short-term in nature. Expenses are recognized when incurred. Allowances for Uncollectible Accounts and Revenue Adjustments We maintain an allowance for uncollectible accounts for estimated losses resulting from the inability of our customers to make required payments. We estimate this allowance by analyzing the aging of our customer receivables, our historical loss experience and other trends and factors affecting the credit risk of our customers, including anticipated changes to future performance. Write-offs occur when we determine an account to be uncollectible and could differ from our allowance estimate as a result of factors such as changes in the overall economic environment or risks surrounding our customers. Additional allowances may be required if the financial condition of our customers were to deteriorate, resulting in an impairment of their ability to make payments. We periodically review the underlying assumptions in our estimate of the allowance for uncollectible accounts to ensure that the allowance reflects the most recent trends and factors. We also maintain an allowance for estimated revenue adjustments resulting from future billing corrections, customer allowances, money-back service guarantees and other miscellaneous revenue adjustments. These revenue adjustments are recorded in our revenue from operations. We us e historical experience, trends, current information and anticipated changes to future performance to update and evaluate these estimates. Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist principally of customer receivables. We perform initial and ongoing credit evaluations of our customers to minimize credit risk. We generally do not require collateral but may require prepayment of our services under certain circumstances. Credit risk is generally diversified due to the large number of entities comprising our customer base and their dispersion across many different industries and geographic regions. Cash and Cash Equivalents We consider cash on hand and deposits in banks along with certificates of deposit and short-term marketable securities with original maturities of three months or less as cash and cash equivalents. Short-term Investments The Company’s investments in certificates of deposit, U.S. government securities, and commercial paper with an original maturity of greater Property and Equipment Property and equipment are stated at cost. Major additions and improvements are capitalized, while maintenance and repairs that do not improve or extend the lives of the respective assets are charged to expense as incurred. We capitalize the cost of tires mounted on purchased revenue equipment as a part of the total equipment cost. Subsequent replacement tires are expensed at the time those tires are placed in service. We assess the realizable value of our long-lived assets and evaluate such assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Depreciation of property and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The following table provides the estimated useful lives by asset type: Structures 7 to 30 years Revenue equipment 4 to 15 years Other equipment 2 to 20 years Leasehold improvements Lesser of economic life or life of lease Depreciation expense was $261.3 million, $253.7 million and $230.4 million for 2020, 2019 and 2018, respectively. Claims and Insurance Accruals We carry a significant amount of insurance with third-party insurance carriers that provides various levels of protection for our risk exposure, including protection in the areas of property, casualty, cyber, management, and group health, with coverage limits and retention and deductible levels that we believe are reasonable given historical claim activity and severity. We believe that our policy of maintaining self-insured retentions or deductibles under these various insurance programs for a portion of our risks, supported by our safety, claims management and loss prevention programs, is an effective means of managing insurance costs. We periodically review our risk exposure and insurance coverage applicable to those risks and believe that we maintain sufficient insurance coverage. Claims and insurance accruals reflect the estimated cost of claims for cargo loss and damage, BIPD, workers’ compensation, group health and group dental. These accruals include amounts for future claims development and claims incurred but not reported, which are primarily based on historical claims development experience. The related cost for cargo loss and damage and BIPD is charged to “Insurance and claims” on our Statements of Operations, while the related costs for workers’ compensation, group health and group dental are charged to “Salaries, wages and benefits” on our Statements of Operations. Our liability for claims and insurance totaled $ million and $ 141.1 million at December 31, 20 20 and 201 9 , respectively. The long-term portions of those reserves were $ million and $ 86.7 million for 20 20 and 201 9 , respectively, which were included in “Other non-current liabilities” on our Balance Sheets . Share-Based Compensation We have various share-based compensation plans for our employees and non-employee directors. Our share-based compensation includes awards of phantom stock, restricted stock, and performance-based restricted stock units which are accounted for under ASC Topic 718, Compensation - Stock Compensation Cash settled phantom stock awards are accounted for as a liability under ASC Topic 718 and changes in the fair value of our liability are recognized as compensation cost over the remaining requisite service period. Changes in the fair value of the liability that occur after the requisite service period are recognized as compensation cost during the period in which the changes occur. We remeasure the liability for the outstanding awards at the end of each reporting period and the compensation cost is based on the change in fair market value for each reporting period. In December 2019, we modified our employee and director phantom stock plans to permit the settlement of outstanding phantom stock awards in shares of the Company’s common stock in lieu of cash settlement. Awards for plan participants electing to settle their awards in stock were amended and certain vesting provisions were waived. Modified awards are accounted for as equity awards rather than liability awards under ASC Topic 718, as they are settled in common stock rather than cash. The total compensation cost of the amended awards was remeasured on the modification date. Any excess over the previously recognized compensation cost will be recognized on a straight-line basis over the requisite remaining period. Awards of restricted stock and performance-based restricted stock units are accounted for as equity under ASC Topic 718. We recognize compensation cost, net of estimated forfeitures, for restricted stock awards on a straight-line basis over the requisite service period of each award. Compensation cost for performance-based restricted stock unit awards is recognized using the accelerated attribution method over the requisite service period of each award. At the end of each reporting period, we reassess the probability of achieving performance targets and changes to our initial assessment are reflected in the reporting period in which the change in estimate occurs. Advertising The costs of advertising our services are expensed as incurred and are included in “General supplies and expenses” on our Statements of Operations. Advertising costs charged to expense totaled $19.0 million, $28.3 million and $28.2 million for 2020, 2019 and 2018, respectively. Common Stock Split On February 21, 2020, we announced that our Board of Directors approved a three-for-two All references in this report to shares outstanding, weighted average shares outstanding, earnings per share, and dividends per share amounts have been restated retroactively to reflect this stock split. Split-adjusted per-share metrics may not recalculate precisely due to rounding . Fair Value of Financial Instruments Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The levels of inputs used to measure fair value are: • Level 1 — Quoted prices for identical instruments in active • Level 2 — Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets; and • Level 3 — Valuations based on inputs that are unobservable, generally utilizing pricing models or other valuation techniques that reflect management’s judgment and estimates. Our short-term investments and our long-term debt, including current maturities, are measured at fair value on a recurring basis, and are further described in Note 9. Our other financial securities in current assets and current liabilities approximate their fair value due to the short-term maturities of these instruments. Stock Repurchase Program On May 1, 2020, we announced that our Board of Directors had approved a new two-year stock repurchase program authorizing us to repurchase up to an aggregate of $700.0 million of our outstanding common stock (the “2020 Repurchase Program”). The 2020 Repurchase Program became effective upon the termination of our $350.0 million repurchase program on May 29, 2020, as of which date $21.5 million remained authorized under the prior program. Under the 2020 Repurchase Program, we may repurchase shares from time to time in open market purchases or through privately negotiated transactions. Shares of our common stock repurchased under our repurchase programs are canceled at the time of repurchase and are classified as authorized but unissued shares of our common stock. As of December 31, 2020, we had $555.2 million remaining Comprehensive Income The Company has no components of other comprehensive income. Accordingly, net income equals comprehensive income for all periods presented in this report. Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments – Credit Losses – Measurement of Credit Losses on Financial Statements” (Topic 326). This ASU modified the methodology for establishing a provision against financial assets, including customer receivables, to include an expected future performance component. We adopted ASU 2016-13 on January 1, 2020. The adoption did not have a material impact to our financial position, results of operations, or cash flow.

Long-term Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-term Debt	Note 2. Long-term Debt Long- term December 31, (In thousands) 2020 2019 Senior notes $ 99,931 $ 45,000 Revolving credit facility — — Total long-term debt 99,931 45,000 Less: Current maturities — — Total maturities due after one year $ 99,931 $ 45,000 Senior Note Agreements We had an unsecured senior note agreement with a principal amount outstanding of $45.0 million at December 31, 2019 (the “Senior Note”). The agreement for the Senior Note called for a scheduled principal payment of $45.0 million, with an interest rate of 4.79%, on January 3, 2021, which was paid in the fourth quarter of 2020. On May 4, 2020, we entered into a Note Purchase and Private Shelf Agreement with PGIM, Inc. (“Prudential”) and certain affiliates and managed accounts of Prudential (the “Note Agreement”). The Note Agreement, which is uncommitted and subject to Prudential’s sole discretion, provides for the issuance of senior promissory notes with an aggregate principal amount of up to $350.0 million through May 4, 2023. Pursuant to the Note Agreement, we issued $ 100.0 million aggregate principal amount of senior promissory notes (the “Series B Notes”), the proceeds of which are available for capital expenditures, share repurchases, dividends, a cquisitions, or general corporate purposes. Borrowing availability under the Note Agreement is reduced by the outstanding amount of the existing Series B Notes, and all other senior promissory notes issued pursuant to the Note Agreement. The Series B Notes bear interest at 3.10% per annum and mature on May 4, 2027, unless prepaid. Principal payments are required annually beginning on May 4, 2023 in equal installments of $20.0 million through May 4, 2027. The Series B Notes are senior unsecured obligations and rank pari passu with our other senior unsecured indebtedness. Credit Agreement On November 21, 2019, we entered into a second amended and restated credit agreement with Wells Fargo Bank, National Association serving as administrative agent for the lenders (the “Credit Agreement”). The Credit Agreement provides for a five-year, $250.0 million senior unsecured revolving line of credit and a $150.0 million accordion feature, which if fully exercised and approved, would expand the total borrowing capacity up to an aggregate of $400.0 million. Of the $250.0 million line of credit commitments under the Credit Agreement, up to $100.0 million may be used for letters of credit. At our For periods The Credit There were 42.1 million General Debt Provisions The Credit Agreement and Note Agreement contain customary covenants, including financial covenants that require us to observe a maximum ratio of debt to total capital and a minimum fixed charge coverage ratio. The Credit Agreement and Note Agreement also include a provision limiting our ability to make restricted payments, including dividends and payments for share repurchases, unless, among other conditions, no defaults or events of default are ongoing (or would be caused by such restricted payment).

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Note 3. Leases We lease certain assets under operating leases, which at December 31, 2020 primarily consist of real estate leases for 27 of our 244 service center locations and automotive leases for private passenger vehicles. Certain operating leases provide for renewal options, which can vary by lease and are typically offered at their fair rental value. We have not made any residual value guarantees related to our operating leases; therefore, we have no corresponding liability recorded on our Balance Sheets. The right-of-use assets and corresponding lease liabilities on our Balance Sheet represent payments over the lease term, which includes renewal options for certain real estate leases that we are likely to exercise. These renewal options begin in 2021 and continue through 2033, and range from one to ten years Of our total lease liabilities, $13.0 million and $10.4 million are liabilities,” and $93.3 million and $56.1 million are $104.4 million Future lease payments for assets under operating leases, as well as a reconciliation to our total lease liabilities as of December 31, 2020, are as follows: (In thousands) Lease Payments (a) 2021 $ 16,017 2022 14,011 2023 12,688 2024 11,278 2025 10,052 Thereafter 63,790 Total lease payments $ 127,836 Less: imputed interest (21,519 ) Total lease liabilities $ 106,317 (a) Lease payments include lease extensions that are reasonably certain to be exercised The weighted average lease term for our operating leases was 9.4 years at each of December 31, 2020 and 2019, respectively. The discount rate used in the calculation of our right-of-use assets and corresponding lease liabilities was determined based on the stated rate within each contract when available, or our collateralized borrowing rate from lending institutions. The weighted average discount rate for our operating leases was 3.1% and 4.0% as of December 31, 2020 and 2019, respectively. Cash paid for amounts included in the measurement of our operating leases was $14.5 million and $14.3 million for the years ended December 31, 2020 and 2019, respectively. Aggregate expense under operating leases was $16.0 million, $14.7 million and $12.6 million for 2020, 2019 and 2018, respectively. Certain operating leases include rent escalation provisions, which we recognize as expense on a straight-line basis. Lease expense is presented within “Operating supplies and expenses” or “General supplies and expenses,” depending on the nature of the use of the leased asset. During the years ended December 31, 2020 and 2019, we added $51.1 million and $8.3 million of right-of-use assets, respectively, in exchange for new operating lease liabilities.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 4. Income Taxes The components of the provision for income taxes are as follows: Year Ended December 31, (In thousands) 2020 2019 2018 Current: Federal $ 216,469 $ 152,836 $ 113,491 State 53,224 42,438 38,647 269,693 195,274 152,138 Deferred: Federal (35,372 ) 12,013 49,125 State (5,639 ) 1,144 8,582 (41,011 ) 13,157 57,707 Total provision for income taxes $ 228,682 $ 208,431 $ 209,845 The following is a reconciliation of income tax expense calculated using the U.S. statutory federal income tax rate with our income tax expense for 2020, 2019 and 2018: Year Ended December 31, (In thousands) 2020 2019 2018 Tax provision at statutory rate $ 189,287 $ 173,029 $ 171,258 State income taxes, net of federal benefit 39,098 35,507 36,396 Other, net 297 (105 ) 2,191 Total provision for income taxes $ 228,682 $ 208,431 $ 209,845 Deferred tax assets and liabilities, which are included in “Other assets” and “Deferred income taxes” on our Balance Sheets, consist of the following: December 31, (In thousands) 2020 2019 Deferred tax assets: Claims and insurance reserves $ 28,863 $ 28,390 Accrued vacation 15,867 17,642 Deferred compensation 43,134 42,417 Other 29,451 11,843 Total deferred tax assets 117,315 100,292 Deferred tax liabilities: Depreciation and amortization (330,751 ) (354,762 ) Other (3,640 ) (3,617 ) Total deferred tax liabilities (334,391 ) (358,379 ) Net deferred tax liability $ (217,076 ) $ (258,087 ) We are subject to U.S. federal income tax, as well as income tax of multiple state tax jurisdictions. We remain open to examination by the Internal Revenue Service for tax years 2017 through 2020. We also remain open to examination by various state tax jurisdictions for tax years 2016 through 2020. The Company’s liability for unrecognized tax benefits was immaterial as of December 31, 2020 and 2019. Interest and penalties related to uncertain tax positions, which are immaterial, are recorded in our “Provision for income taxes” on our Statements of Operations. Changes in our liability for unrecognized tax benefits could affect our effective tax rate, if recognized, but we do not expect any material changes within the next twelve months.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Note 5. Related Party Transactions Each of Earl E. Congdon, David S. Congdon and John R. Congdon, Jr. are related to one another and served in various management positions and/or on our Board of Directors during 2020. Our employment agreement with David S. Congdon is incorporated by reference as an exhibit to this Annual Report on Form 10-K. We regularly disclose the amount of compensation that we pay to these individuals, as well as the compensation paid to any of their family members employed by us that from time to time may require disclosure, in the proxy statement for our Annual Meeting of Shareholders.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	Note 6. Employee Benefit Plans Defined Contribution Plan Full-time employees meeting certain eligibility requirements are automatically enrolled in our 401(k) employee retirement plan. Employee contributions are limited to a percentage of the employee’s compensation, as defined in the plan. We match a percentage of our employees’ contributions up to certain maximum limits. In addition, we may also provide a discretionary matching contribution as specified in the plan. Our employer contributions, net of forfeitures, for 2020, 2019 and 2018 were $65.4 million, $60.4 million and $59.8 million, respectively. Deferred Compensation Plan We maintain a nonqualified deferred compensation plan for the benefit of certain eligible employees, including those whose contributions to the 401(k) employee retirement plan are limited due to provisions of the Internal Revenue Code. Participating employees may elect to defer receipt of a percentage of their compensation, as defined in the plan, and the deferred amount is credited to each participant’s deferred compensation account. The plan is not funded, and the Company does not make a matching contribution to this plan. Although the plan is not funded, participants are allowed to select investment options for which their deferrals and future earnings are deemed to be invested. Participant accounts are adjusted to reflect participant deferrals and the performance of their deemed investments. The amounts owed to the participants totaled $84.2 million and $75.4 million at December 31, 2020 and 2019, respectively, of which $79.1 million and $71.4 million were included in “Other non-current liabilities” on our Balance Sheets as of December 31, 2020 and 2019, respectively.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Note 7. Earnings Per Share Basic earnings per share is computed by dividing net income by the daily weighted average number of shares of our common stock outstanding for the period, excluding unvested restricted stock. Unvested restricted stock is included in common shares outstanding on our Balance Sheets. Diluted earnings per share is computed using the treasury stock method. The denominator used in calculating diluted earnings per share includes the impact of unvested restricted stock and other dilutive, non-participating securities under our equity award agreements. The denominator excludes contingently-issuable shares under performance-based award agreements when the performance target has not yet been deemed achieved. The following table provides a reconciliation of the number of shares of common stock used in computing basic and diluted earnings per share: Year Ended December 31, (In thousands) 2020 2019 2018 Weighted average shares outstanding - basic 117,737,180 120,414,218 122,885,346 Dilutive effect of share-based awards 756,023 195,381 144,326 Weighted average shares outstanding - diluted 118,493,203 120,609,599 123,029,672

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	Note 8. Share-Based Compensation Stock Incentive Plan On May 19, 2016, our shareholders approved the Old Dominion Freight Line, Inc. 2016 Stock Incentive Plan (the “Stock Incentive Plan”) previously approved by our Board of Directors. The Stock Incentive Plan, under which awards may be granted until May 18, 2026 or the Stock Incentive Plan’s earlier termination, serves as our primary equity incentive plan and provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted awards, performance awards, phantom stock awards and other stock-based awards or dividend equivalent awards to selected employees and non-employee directors. The maximum number of shares of common stock that we may issue or deliver pursuant to awards granted under the Stock Incentive Plan is 3,000,000 shares. Restricted Stock Awards During 2020, 2019 and 2018, we granted restricted stock awards to selected employees and non-employee directors under the Stock Incentive Plan. The employee restricted stock awards vest in three equal annual installments on each anniversary of the grant date, and the non-employee director restricted stock awards generally vest in full on the first anniversary of the grant date. In both cases, the restricted stock awards are subject to accelerated vesting due to death, total disability, or change in control of the Company. Subject to the foregoing, unvested restricted stock awards are generally forfeited upon termination of employment. The restricted stock awards accrue dividends while the award is unvested and only carry rights to receive the accrued dividends once vested. Compensation cost for restricted stock awards is measured at the grant date based on the fair market value per share of our common stock. The following table summarizes our restricted stock award activity for employees and non-employee directors: Shares Weighted Average Grant Date Fair Value Per Share Unvested at January 1, 2020 163,723 $ 90.65 Granted 75,638 149.38 Vested (80,349 ) 85.68 Forfeited (19,149 ) 117.86 Unvested at December 31, 2020 139,863 $ 121.53 The weighted average grant date fair value per restricted stock award granted during fiscal years 2020, 2019 and 2018 was $149.38, $96.59 and $91.85, respectively. The total fair value of vested restricted stock awards for fiscal year 2020, 2019 and 2018 was $11.9 million, $7.3 million and $6.2 million, respectively. At December 31, 2020, the Company had $9.9 million of unrecognized stock-based compensation cost, net of estimated forfeitures, related to unvested restricted stock awards that are expected to be recognized over a weighted average period of 1.7 years. Performance-Based Restricted Stock Units During 2020 and 2019, we granted performance-based restricted stock units (“PBRSUs”) to selected employees under the Stock Incentive Plan. The PBRSUs are earned based on the achievement of stated Company performance metrics over a one-year performance period. One-third of the earned PBRSUs vest following the end of the one-year performance period if the performance metrics are satisfied, with an additional one-third of the PBRSUs vesting on each of the next two grant date anniversaries. Earned PBRSUs are subject to accelerated vesting due to death, total disability, or change in control of the Company. Subject to the foregoing, unvested PBRSUs are generally forfeited if minimum threshold performance targets are not achieved or upon termination of employment. The PBRSUs do not include dividend participation rights. Compensation cost for PBRSUs is measured at the grant date based on the fair market value per share of our common stock, with consideration given to the probability of achieving performance targets. At the end of each reporting period, we reassess the probability of achieving performance targets and changes to our initial assessment are reflected in the reporting period in which the change in estimate occurs. All PBRSUs granted in 2019 were forfeited as the performance metrics were not met. The following table summarizes our activity for PBRSUs for employees during 2020: Shares Weighted Average Grant Date Fair Value Per Share Unvested at January 1, 2020 — $ — Granted (a) 31,072 146.29 Vested — — Forfeited — — Unvested at December 31, 2020 31,072 $ 146.29 (a) Amount represents PBRSUs granted at target. PBRSUs earned may range from zero to 200% of the target award. Actual PBRSUs earned for the 2020 performance period, as determined by the Compensation Committee, were equal to the target amount. At December 31, 2020, the Company had $1.9 million of unrecognized stock-based compensation cost, net of estimated forfeitures, related to unvested PBRSUs that are expected to be recognized over a weighted average period of 2.1 years. Phantom Stock Plan Employee Plans On October 30, 2012, our Board of Directors approved, and we adopted the Old Dominion Freight Line, Inc. 2012 Phantom Stock Plan, as amended on January 29, 2015 and December 16, 2019 (the “2012 Phantom Stock Plan”). Under the 2012 Phantom Stock Plan, 1,500,000 shares of phantom stock may be awarded, each of which represents a contractual right to receive an amount in cash or common stock equal to the fair market value of a share of our common stock on the settlement date, which is the earliest of the date of the participant’s (i) termination of employment for any reason other than for cause, (ii) death or (iii) total disability. Each award vests in 20% increments on the anniversary of the grant date provided that the participant (i) has been continuously employed by us since the grant date, (ii) has been continuously employed by us for ten years, and (iii) has reached the age of 65 (with respect to the cash settlement option). Vesting also occurs on the earliest of (i) a change in control, (ii) death or (iii) total disability. Awards are settled in cash or common stock after the required vesting period has been satisfied and upon termination of employment. Unvested shares are forfeited upon termination of employment, although our Board of Directors has authority to modify and/or accelerate the vesting of awards. On May 16, 2005, our Board of Directors approved, and the Company adopted, the Old Dominion Freight Line, Inc. Phantom Stock Plan, as amended January 1, 2009, May 18, 2009, May 17, 2011, January 29, 2015 and December 16, 2019 (the “2005 Phantom Stock Plan” and, together with the 2012 Phantom Stock Plan, the “Employee Phantom Plans”). The 2005 Phantom Stock Plan expired in May 2012; however, grants under the 2005 Phantom Stock Plan remain outstanding. Each share of phantom stock awarded to eligible employees under the 2005 Phantom Stock Plan represents a contractual right to receive an amount in cash or common stock equal to the fair market value of a share of our common stock on the settlement date, which generally is the earlier of the eligible employee’s (i) termination from the Company after reaching 55 years of age (with respect to the cash settlement option), (ii) death, or (iii) total disability. Awards are settled in cash after the required vesting period has been satisfied and upon termination of employment. Awards under the 2005 Phantom Stock Plan vest upon the earlier to occur of the following: (i) the date of a change of control in our ownership; (ii) the fifth anniversary of the grant date of the award, provided the participant is employed by us on that date; (iii) the date of the participant’s death while employed by us; (iv) the date of the participant’s total disability; or (v) with respect to the cash settlement option, the date the participant attains the age of 65 while employed by us. Awards that are not vested upon terminatio n of employment are forfeited . The 2005 Phantom Stock Plan does, however, provide the Board of Directors with discretionary authority to modify and/or accelerate the vesting of awards. On December 16, 2019, our Board of Directors approved, and the Company adopted, amendments to the Employee Phantom Plans. The amendments permit settlement of outstanding phantom stock awards in shares of the Company’s common stock in lieu of cash settlement, among other administrative changes. For employees who elected to amend their phantom stock awards under the Employee Phantom Plans and settle awards in common stock, the amended award agreements also provide for waivers of the age 65 and age 55 vesting provisions required by the 2012 Phantom Stock Plan and the 2005 Phantom Stock Plan, respectively. Director Plan On May 28, 2008, our Board of Directors approved, and the Company adopted, the Old Dominion Freight Line, Inc. Director Phantom Stock Plan, as amended April 1, 2011, February 20, 2014, August 7, 2014, February 25, 2016 and December 16, 2019 (the “Director Phantom Stock Plan” and together with the Employee Phantom Plans, the “Phantom Plans”). Under the Director Phantom Stock Plan, each eligible non-employee director was granted an annual award of phantom shares. Our Board of Directors approved the initial grant under this plan at its May 2008 meeting and authorized the subsequent annual grants to be made thereafter. For each vested phantom share, participants are entitled to an amount in cash or common stock equal to the fair market value of the award on the date that service as a director terminates for any reason. Our shareholders approved the Stock Incentive Plan at our 2016 Annual Meeting of Shareholders; as a result, no phantom shares have been granted under the Phantom Plans since such approval. Director Phantom Stock Plan awards vest upon the earlier to occur of the following: (i) the one-year anniversary of the grant date; (ii) the date of the first annual meeting of shareholders that occurs after the grant date provided the participant is still in service as a director; (iii) the date of a change of control in our ownership provided that the participant is still in service as a director; or (iv) the date of the participant’s death or total disability while still in service as a director. Awards that are not vested upon termination of service as a director are forfeited. On December 16, 2019, our Board of Directors approved, and the Company adopted, an amendment to the Director Phantom Stock Plan. The amendment permits settlement of outstanding phantom stock awards in shares of the Company’s common stock in lieu of cash settlement, among other administrative changes. Accounting Impact Modified awards are accounted for as equity awards rather than liability awards under ASC Topic 718, Compensation - Stock Compensation, as they are settled in common stock rather than cash. In December 2019, awards for 613,996 employee and director phantom shares were modified to settle in shares of the Company’s common stock. These modified awards have a weighted average grant date fair value per share of $120.41. A summary of the changes in the number of outstanding phantom stock awards during the year ended December 31, 2020 for the Phantom Plans is provided below: Employee Phantom Plans Director Phantom Stock Plan Total Balance of shares outstanding at December 31, 2019 637,755 81,106 718,861 Granted — — — Settled (104,865 ) — (104,865 ) Forfeited — — — Balance of shares outstanding at December 31, 2020 532,890 81,106 613,996 All phantom shares outstanding at December 31, 2020 relate to modified awards. Of these outstanding awards, 600,719 phantom shares were vested at December 31, 2020 with a weighted average grant date fair value per share of $120.56. The remaining phantom shares are unvested and have a weighted average grant date fair value per share of $113.65. There were no unsettled phantom stock awards accounted for as a liability under the Phantom Plans as of December 31, 2020. While the Stock Incentive Plan currently serves as our primary equity plan, the terms of the Phantom Stock Plans and related award agreements will continue to govern all awards granted under the Phantom Stock Plans until such awards have been settled, forfeited, canceled or have otherwise expired or terminated.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 9. Fair Value Measurements Short-term investments A summary of the fair value of our short-term investments as of December 31, 2020 is shown in the table below. December 31, 2020 Level 1 Level 2 Level 3 Certificates of deposit $ 75,032 $ — $ 75,032 $ — U.S. government securities 125,379 125,379 — — Commercial paper 129,863 — 129,863 — Total $ 330,274 $ 125,379 $ 204,895 $ — Our certificates of deposit are measured at carrying value including accrued interest, which approximates fair value due to their short-term nature. Our commercial paper is valued using broker quotes that utilize observable market inputs. Long-term debt The carrying value of our total long-term debt, including current maturities, was $99.9 million and $45.0 million at December 31, 2020 and 2019, respectively. The estimated fair value of our total long-term debt, including current maturities, was $105.4 million and $46.1 million at December 31, 2020 and 2019, respectively. The fair value measurement of our senior notes was determined using a discounted cash flow analysis that factors in current market yields for comparable borrowing arrangements under our credit profile. Since this methodology is based upon market yields for comparable arrangements, the measurement is categorized as Level 2 under the three-level fair value hierarchy as established by the Financial Accounting Standards Board.

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments And Contingencies	Note 10. Commitments and Contingencies We are involved in or addressing various legal proceedings and claims, governmental inquiries, notices and investigations that have arisen in the ordinary course of our business and have not been fully adjudicated, some of which may be covered in whole or in part by insurance. Certain of these matters include collective and/or class-action allegations. We do not believe that the resolution of any of these matters will have a material adverse effect upon our financial position, results of operations or cash flows.

Schedule II - Valuation And Qua

Schedule II - Valuation And Qualifying Accounts	12 Months Ended
	Dec. 31, 2020
Valuation And Qualifying Accounts [Abstract]
Schedule II Valuation And Qualifying Accounts	The Schedule II – Valuation and Qualifying Accounts schedule of Old Dominion Freight Line, Inc. is included below: Schedule II Old Dominion Freight Line, Inc. Valuation and Qualifying Accounts (In thousands) Allowance for Uncollectible Accounts (1) Year Ended December 31, Balance at Beginning of Period Charged to Expense Deductions (2) Balance at End of Period 2018 $ 3,488 $ 3,846 $ 3,702 $ 3,632 2019 $ 3,632 $ 2,113 $ 2,248 $ 3,497 2020 $ 3,497 $ 3,248 $ 2,650 $ 4,095 (1) This table does not include any allowances for revenue adjustments that result from billing corrections, customer allowances, money-back service guarantees and other miscellaneous revenue adjustments that are recorded in our revenue from operations. ( 2) Uncollectible accounts written off, net of recoveries. All other schedules for which provision is made in the applicable accounting regulations of the SEC are not required under the instructions thereto or are inapplicable and, therefore, have been omitted.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Business	Business We are one of the largest North American less-than-truckload (“LTL”) motor carriers. We provide regional, inter-regional and national LTL services through a single integrated, union-free organization. Our service offerings, which include expedited transportation, are provided through an expansive network of service centers located throughout the continental United States. Through strategic alliances, we also provide LTL services throughout North America. In addition to our core LTL services, we offer a range of value-added services including container drayage, truckload brokerage and supply chain consulting. We have one operating segment and no single customer exceeds 5% of our revenue. The composition of our revenue is summarized below: Year Ended December 31, (In thousands) 2020 2019 2018 LTL services $ 3,961,054 $ 4,055,467 $ 3,982,658 Other services 54,075 53,644 61,037 Total revenue $ 4,015,129 $ 4,109,111 $ 4,043,695
Basis of Presentation	Basis of Presentation The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Certain amounts in prior years have been reclassified to conform prior years’ financial statements to the current presentation. Unless the context requires otherwise, references in these Notes to “Old Dominion,” the “Company,” “we,” “us” and “our” refer to Old Dominion Freight Line, Inc.
Revenue and Expense Recognition	Revenue and Expense Recognition We recognize revenue based upon when our transportation and related services have been completed in accordance with the bill of lading (“BOL”) contract, our general tariff provisions and contractual agreements with our customers. Generally, our performance obligations begin when we receive a BOL from a customer and are satisfied when we complete the delivery of a shipment and related services. We recognize revenue for our performance obligations under our customer contracts over time, as our customers receive the benefits of our services in accordance with Accounting Standards Update (“ASU”) 2014-09. With respect to services not completed at the end of a reporting period, we use a percentage of completion method to allocate the appropriate revenue to each separate reporting period. Under this method, we develop a factor for each uncompleted shipment by dividing the actual number of days in transit at the end of a reporting period by that shipment’s standard delivery time schedule. This factor is applied to the total revenue for that shipment and revenue is allocated between reporting periods accordingly. Payment terms vary by customer and are short-term in nature. Expenses are recognized when incurred.
Allowances for Uncollectible Accounts and Revenue Adjustments	Allowances for Uncollectible Accounts and Revenue Adjustments We maintain an allowance for uncollectible accounts for estimated losses resulting from the inability of our customers to make required payments. We estimate this allowance by analyzing the aging of our customer receivables, our historical loss experience and other trends and factors affecting the credit risk of our customers, including anticipated changes to future performance. Write-offs occur when we determine an account to be uncollectible and could differ from our allowance estimate as a result of factors such as changes in the overall economic environment or risks surrounding our customers. Additional allowances may be required if the financial condition of our customers were to deteriorate, resulting in an impairment of their ability to make payments. We periodically review the underlying assumptions in our estimate of the allowance for uncollectible accounts to ensure that the allowance reflects the most recent trends and factors. We also maintain an allowance for estimated revenue adjustments resulting from future billing corrections, customer allowances, money-back service guarantees and other miscellaneous revenue adjustments. These revenue adjustments are recorded in our revenue from operations. We us e historical experience, trends, current information and anticipated changes to future performance to update and evaluate these estimates.
Credit Risk	Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist principally of customer receivables. We perform initial and ongoing credit evaluations of our customers to minimize credit risk. We generally do not require collateral but may require prepayment of our services under certain circumstances. Credit risk is generally diversified due to the large number of entities comprising our customer base and their dispersion across many different industries and geographic regions.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider cash on hand and deposits in banks along with certificates of deposit and short-term marketable securities with original maturities of three months or less as cash and cash equivalents.
Short-term Investments	Short-term Investments The Company’s investments in certificates of deposit, U.S. government securities, and commercial paper with an original maturity of greater
Property and Equipment	Property and Equipment Property and equipment are stated at cost. Major additions and improvements are capitalized, while maintenance and repairs that do not improve or extend the lives of the respective assets are charged to expense as incurred. We capitalize the cost of tires mounted on purchased revenue equipment as a part of the total equipment cost. Subsequent replacement tires are expensed at the time those tires are placed in service. We assess the realizable value of our long-lived assets and evaluate such assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Depreciation of property and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The following table provides the estimated useful lives by asset type: Structures 7 to 30 years Revenue equipment 4 to 15 years Other equipment 2 to 20 years Leasehold improvements Lesser of economic life or life of lease Depreciation expense was $261.3 million, $253.7 million and $230.4 million for 2020, 2019 and 2018, respectively.
Claims and Insurance Accruals	Claims and Insurance Accruals We carry a significant amount of insurance with third-party insurance carriers that provides various levels of protection for our risk exposure, including protection in the areas of property, casualty, cyber, management, and group health, with coverage limits and retention and deductible levels that we believe are reasonable given historical claim activity and severity. We believe that our policy of maintaining self-insured retentions or deductibles under these various insurance programs for a portion of our risks, supported by our safety, claims management and loss prevention programs, is an effective means of managing insurance costs. We periodically review our risk exposure and insurance coverage applicable to those risks and believe that we maintain sufficient insurance coverage. Claims and insurance accruals reflect the estimated cost of claims for cargo loss and damage, BIPD, workers’ compensation, group health and group dental. These accruals include amounts for future claims development and claims incurred but not reported, which are primarily based on historical claims development experience. The related cost for cargo loss and damage and BIPD is charged to “Insurance and claims” on our Statements of Operations, while the related costs for workers’ compensation, group health and group dental are charged to “Salaries, wages and benefits” on our Statements of Operations. Our liability for claims and insurance totaled $ million and $ 141.1 million at December 31, 20 20 and 201 9 , respectively. The long-term portions of those reserves were $ million and $ 86.7 million for 20 20 and 201 9 , respectively, which were included in “Other non-current liabilities” on our Balance Sheets .
Share-Based Compensation	Share-Based Compensation We have various share-based compensation plans for our employees and non-employee directors. Our share-based compensation includes awards of phantom stock, restricted stock, and performance-based restricted stock units which are accounted for under ASC Topic 718, Compensation - Stock Compensation Cash settled phantom stock awards are accounted for as a liability under ASC Topic 718 and changes in the fair value of our liability are recognized as compensation cost over the remaining requisite service period. Changes in the fair value of the liability that occur after the requisite service period are recognized as compensation cost during the period in which the changes occur. We remeasure the liability for the outstanding awards at the end of each reporting period and the compensation cost is based on the change in fair market value for each reporting period. In December 2019, we modified our employee and director phantom stock plans to permit the settlement of outstanding phantom stock awards in shares of the Company’s common stock in lieu of cash settlement. Awards for plan participants electing to settle their awards in stock were amended and certain vesting provisions were waived. Modified awards are accounted for as equity awards rather than liability awards under ASC Topic 718, as they are settled in common stock rather than cash. The total compensation cost of the amended awards was remeasured on the modification date. Any excess over the previously recognized compensation cost will be recognized on a straight-line basis over the requisite remaining period. Awards of restricted stock and performance-based restricted stock units are accounted for as equity under ASC Topic 718. We recognize compensation cost, net of estimated forfeitures, for restricted stock awards on a straight-line basis over the requisite service period of each award. Compensation cost for performance-based restricted stock unit awards is recognized using the accelerated attribution method over the requisite service period of each award. At the end of each reporting period, we reassess the probability of achieving performance targets and changes to our initial assessment are reflected in the reporting period in which the change in estimate occurs.
Advertising	Advertising The costs of advertising our services are expensed as incurred and are included in “General supplies and expenses” on our Statements of Operations. Advertising costs charged to expense totaled $19.0 million, $28.3 million and $28.2 million for 2020, 2019 and 2018, respectively.
Common Stock Split	Common Stock Split On February 21, 2020, we announced that our Board of Directors approved a three-for-two All references in this report to shares outstanding, weighted average shares outstanding, earnings per share, and dividends per share amounts have been restated retroactively to reflect this stock split. Split-adjusted per-share metrics may not recalculate precisely due to rounding .
Fair Values of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The levels of inputs used to measure fair value are: • Level 1 — Quoted prices for identical instruments in active • Level 2 — Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets; and • Level 3 — Valuations based on inputs that are unobservable, generally utilizing pricing models or other valuation techniques that reflect management’s judgment and estimates. Our short-term investments and our long-term debt, including current maturities, are measured at fair value on a recurring basis, and are further described in Note 9. Our other financial securities in current assets and current liabilities approximate their fair value due to the short-term maturities of these instruments.
Stock Repurchase Program	Stock Repurchase Program On May 1, 2020, we announced that our Board of Directors had approved a new two-year stock repurchase program authorizing us to repurchase up to an aggregate of $700.0 million of our outstanding common stock (the “2020 Repurchase Program”). The 2020 Repurchase Program became effective upon the termination of our $350.0 million repurchase program on May 29, 2020, as of which date $21.5 million remained authorized under the prior program. Under the 2020 Repurchase Program, we may repurchase shares from time to time in open market purchases or through privately negotiated transactions. Shares of our common stock repurchased under our repurchase programs are canceled at the time of repurchase and are classified as authorized but unissued shares of our common stock. As of December 31, 2020, we had $555.2 million remaining Comprehensive Income The Company has no components of other comprehensive income. Accordingly, net income equals comprehensive income for all periods presented in this report.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments – Credit Losses – Measurement of Credit Losses on Financial Statements” (Topic 326). This ASU modified the methodology for establishing a provision against financial assets, including customer receivables, to include an expected future performance component. We adopted ASU 2016-13 on January 1, 2020. The adoption did not have a material impact to our financial position, results of operations, or cash flow.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Disaggregated Revenue	We have one operating segment and no single customer exceeds 5% of our revenue. The composition of our revenue is summarized below: Year Ended December 31, (In thousands) 2020 2019 2018 LTL services $ 3,961,054 $ 4,055,467 $ 3,982,658 Other services 54,075 53,644 61,037 Total revenue $ 4,015,129 $ 4,109,111 $ 4,043,695
Estimated Useful Lives of Property and Equipment	Depreciation of property and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The following table provides the estimated useful lives by asset type: Structures 7 to 30 years Revenue equipment 4 to 15 years Other equipment 2 to 20 years Leasehold improvements Lesser of economic life or life of lease

Long-term Debt (Tables)

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt, Net of Unamortized Debt Issuance Costs	Long- term December 31, (In thousands) 2020 2019 Senior notes $ 99,931 $ 45,000 Revolving credit facility — — Total long-term debt 99,931 45,000 Less: Current maturities — — Total maturities due after one year $ 99,931 $ 45,000

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Future Lease Payments for Assets under Operating Leases, as well as Reconciliation to Lease Liability	Future lease payments for assets under operating leases, as well as a reconciliation to our total lease liabilities as of December 31, 2020, are as follows: (In thousands) Lease Payments (a) 2021 $ 16,017 2022 14,011 2023 12,688 2024 11,278 2025 10,052 Thereafter 63,790 Total lease payments $ 127,836 Less: imputed interest (21,519 ) Total lease liabilities $ 106,317 (a) Lease payments include lease extensions that are reasonably certain to be exercised

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Components of the Provision for Income Taxes	The components of the provision for income taxes are as follows: Year Ended December 31, (In thousands) 2020 2019 2018 Current: Federal $ 216,469 $ 152,836 $ 113,491 State 53,224 42,438 38,647 269,693 195,274 152,138 Deferred: Federal (35,372 ) 12,013 49,125 State (5,639 ) 1,144 8,582 (41,011 ) 13,157 57,707 Total provision for income taxes $ 228,682 $ 208,431 $ 209,845
Schedule of Effective Income Tax Reconciliation of the U.S. Statutory Federal Income Tax Rates	The following is a reconciliation of income tax expense calculated using the U.S. statutory federal income tax rate with our income tax expense for 2020, 2019 and 2018: Year Ended December 31, (In thousands) 2020 2019 2018 Tax provision at statutory rate $ 189,287 $ 173,029 $ 171,258 State income taxes, net of federal benefit 39,098 35,507 36,396 Other, net 297 (105 ) 2,191 Total provision for income taxes $ 228,682 $ 208,431 $ 209,845
Schedule of Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities, which are included in “Other assets” and “Deferred income taxes” on our Balance Sheets, consist of the following: December 31, (In thousands) 2020 2019 Deferred tax assets: Claims and insurance reserves $ 28,863 $ 28,390 Accrued vacation 15,867 17,642 Deferred compensation 43,134 42,417 Other 29,451 11,843 Total deferred tax assets 117,315 100,292 Deferred tax liabilities: Depreciation and amortization (330,751 ) (354,762 ) Other (3,640 ) (3,617 ) Total deferred tax liabilities (334,391 ) (358,379 ) Net deferred tax liability $ (217,076 ) $ (258,087 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Reconciliation of Number of Common Stock used in Computing Basic and Diluted Earning Per Share	The following table provides a reconciliation of the number of shares of common stock used in computing basic and diluted earnings per share: Year Ended December 31, (In thousands) 2020 2019 2018 Weighted average shares outstanding - basic 117,737,180 120,414,218 122,885,346 Dilutive effect of share-based awards 756,023 195,381 144,326 Weighted average shares outstanding - diluted 118,493,203 120,609,599 123,029,672

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Restricted Stock Award Activity for Employees and Non-Employee Directors	The following table summarizes our restricted stock award activity for employees and non-employee directors: Shares Weighted Average Grant Date Fair Value Per Share Unvested at January 1, 2020 163,723 $ 90.65 Granted 75,638 149.38 Vested (80,349 ) 85.68 Forfeited (19,149 ) 117.86 Unvested at December 31, 2020 139,863 $ 121.53
Summary of Activity for PBRSUs for Employees	The following table summarizes our activity for PBRSUs for employees during 2020: Shares Weighted Average Grant Date Fair Value Per Share Unvested at January 1, 2020 — $ — Granted (a) 31,072 146.29 Vested — — Forfeited — — Unvested at December 31, 2020 31,072 $ 146.29 (a) Amount represents PBRSUs granted at target. PBRSUs earned may range from zero to 200% of the target award. Actual PBRSUs earned for the 2020 performance period, as determined by the Compensation Committee, were equal to the target amount.
Summary of the Changes in the Number of Outstanding Phantom Stock Shares	A summary of the changes in the number of outstanding phantom stock awards during the year ended December 31, 2020 for the Phantom Plans is provided below: Employee Phantom Plans Director Phantom Stock Plan Total Balance of shares outstanding at December 31, 2019 637,755 81,106 718,861 Granted — — — Settled (104,865 ) — (104,865 ) Forfeited — — — Balance of shares outstanding at December 31, 2020 532,890 81,106 613,996

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Short-term Investments	A summary of the fair value of our short-term investments as of December 31, 2020 is shown in the table below. December 31, 2020 Level 1 Level 2 Level 3 Certificates of deposit $ 75,032 $ — $ 75,032 $ — U.S. government securities 125,379 125,379 — — Commercial paper 129,863 — 129,863 — Total $ 330,274 $ 125,379 $ 204,895 $ —

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020USD ($)SegmentCustomer	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	May 29, 2020USD ($)	May 01, 2020USD ($)
Significant Accounting Policies [Line Items]
Number of operating segment | Segment	1
Number of customer exceeding 5% of revenue | Customer	0
Depreciation expenses	$ 261,300,000	$ 253,700,000	$ 230,400,000
Self-insurance reserve	139,600,000	141,100,000
Long-term portions of self insurance reserve	86,500,000	86,700,000
Allocated share-based compensation expense	14,300,000	42,900,000	10,700,000
Employee service share-based compensation, tax benefit from compensation expense	(3,800,000)	(10,800,000)	(3,200,000)
Advertising expense	$ 19,000,000	$ 28,300,000	$ 28,200,000
Common stock split, description	On February 21, 2020, we announced that our Board of Directors approved a three-for-two split of our common stock for shareholders of record as of the close of business on the record date of March 10, 2020. On March 24, 2020, those shareholders received one additional share of common stock for every two shares owned.
Common stock split, conversion ratio	1.5
2019 Share Repurchase Program [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Stock repurchase program, authorized amount				$ 21,500,000	$ 350,000,000
2020 Share Repurchase Program [Member]
Significant Accounting Policies [Line Items]
Stock repurchase program, remaining authorized repurchase amount	$ 555,200,000
2020 Share Repurchase Program [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Stock repurchase program, authorized amount					$ 700,000,000

Significant Accounting Polici_5

Significant Accounting Policies - (Disaggregated Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from operations	$ 4,015,129	$ 4,109,111	$ 4,043,695
LTL Service Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from operations	3,961,054	4,055,467	3,982,658
Other Service Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from operations	$ 54,075	$ 53,644	$ 61,037

Significant Accounting Polici_6

Significant Accounting Policies - (Estimated Useful Lives Of Property And Equipment) (Details)	12 Months Ended
	Dec. 31, 2020
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset	Lesser of economic life or life of lease
Minimum [Member] | Structures [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset, years	7 years
Minimum [Member] | Revenue Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset, years	4 years
Minimum [Member] | Other Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset, years	2 years
Maximum [Member] | Structures [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset, years	30 years
Maximum [Member] | Revenue Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset, years	15 years
Maximum [Member] | Other Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of asset, years	20 years

Long-term Debt - Schedule of Lo

Long-term Debt - Schedule of Long-term Debt, Net of Unamortized Debt Issuance Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 30, 2019
Debt Disclosure [Abstract]
Senior notes	$ 99,931	$ 45,000
Revolving credit facility		0
Total long-term debt	99,931	45,000
Less: Current maturities		0
Total maturities due after one year	$ 99,931	$ 45,000	$ 45,000

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Details) - USD ($)	May 04, 2023	May 04, 2020	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Senior note			$ 99,931,000	$ 45,000,000
Debt instrument, due date			Jan. 3, 2021
Fixed interest rate			4.79%
Proceeds from issuance of senior promissory notes			$ 99,923,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.10%
Letter of Credit Fee in Percentage			1.00%
Letters of Credit Outstanding, Amount			$ 42,100,000	48,900,000
Series B [Member] | Forecast [Member]
Debt Instrument [Line Items]
Scheduled principal payment	$ 20,000,000
Debt instrument, due date	May 4, 2027
Notes interest	3.10%
Maturity Date Description	The Series B Notes bear interest at 3.10% per annum and mature on May 4, 2027, unless prepaid.
P G I M I N C [Member] | Series B Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of senior promissory notes		$ 100,000,000
Minimum [Member]
Debt Instrument [Line Items]
Interest Rate Spread added to Rate			0.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.10%
Maximum [Member]
Debt Instrument [Line Items]
Interest Rate Spread added to Rate			0.375%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.175%
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate Spread added to Rate			1.00%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate Spread added to Rate			1.375%
2019 Credit Agreement [Member]
Debt Instrument [Line Items]
Original borrowing capacity			$ 250,000,000
Line of Credit Facility Accordion			150,000,000
Line of Credit Facility, Maximum Borrowing Capacity			400,000,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases			100,000,000
Prior Credit Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			300,000,000
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Senior note				$ 45,000,000
Unsecured Senior Note Due January 3, 2021 [Member]
Debt Instrument [Line Items]
Scheduled principal payment			$ 45,000,000
Note Agreement [Member] | Maximum [Member] | P G I M I N C [Member]
Debt Instrument [Line Items]
Aggregate amount on promissory notes issued		$ 350,000,000

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)RealEstateLocation	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Lessee Lease Description [Line Items]
Number of real estate leases | RealEstate	27
Number of service center locations | Location	244
Lessee, operating lease, option to renew, earliest year	2021
Lessee, operating lease, option to renew, latest year	2033
Operating lease, liability, current	$ 13	$ 10.4
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating lease, liability, noncurrent	$ 93.3	$ 56.1
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Operating lease, right-of-use asset	$ 104.4	$ 65.3
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating lease, weighted average remaining lease term	9 years 4 months 24 days	9 years 4 months 24 days
Operating lease, weighted average discount rate, percent	3.10%	4.00%
Cash paid for amounts included in the measurement of operating leases	$ 14.5	$ 14.3
Operating lease, expense	16	14.7	$ 12.6
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 51.1	$ 8.3
Minimum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, renewal term	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, renewal term	10 years

Leases - Future Lease Payments

Leases - Future Lease Payments for Assets under Operating Leases, as well as Reconciliation to Lease Liability (Details) $ in Thousands	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 16,017
2022	14,011
2023	12,688
2024	11,278
2025	10,052
Thereafter	63,790
Total lease payments	127,836
Less: imputed interest	(21,519)
Total lease liabilities	$ 106,317

Income Taxes - Components of th

Income Taxes - Components of the Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 216,469	$ 152,836	$ 113,491
State	53,224	42,438	38,647
Total current income tax expense (benefit)	269,693	195,274	152,138
Deferred:
Federal	(35,372)	12,013	49,125
State	(5,639)	1,144	8,582
Total deferred income tax expense (benefit)	(41,011)	13,157	57,707
Total provision for income taxes	$ 228,682	$ 208,431	$ 209,845

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Reconciliation of the U.S. Statutory Federal Income Tax Rates (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax provision at statutory rate	$ 189,287	$ 173,029	$ 171,258
State income taxes, net of federal benefit	39,098	35,507	36,396
Other, net	297	(105)	2,191
Total provision for income taxes	$ 228,682	$ 208,431	$ 209,845

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Claims and insurance reserves	$ 28,863	$ 28,390
Accrued vacation	15,867	17,642
Deferred compensation	43,134	42,417
Other	29,451	11,843
Total deferred tax assets	117,315	100,292
Depreciation and amortization	(330,751)	(354,762)
Other	(3,640)	(3,617)
Total deferred tax liabilities	(334,391)	(358,379)
Net deferred tax liability	$ (217,076)	$ (258,087)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020
Minimum [Member] | State and Local Jurisdiction [Member]
Income Tax Examination [Line Items]
Income tax examinations year under examination	2016
Minimum [Member] | Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Income tax examinations year under examination	2017
Maximum [Member] | State and Local Jurisdiction [Member]
Income Tax Examination [Line Items]
Income tax examinations year under examination	2020
Maximum [Member] | Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Income tax examinations year under examination	2020

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Company contributions	$ 65.4	$ 60.4	$ 59.8
Deferred compensation plan amounts owed, non current	79.1	71.4
Deferred compensation plan amounts owed	$ 84.2	$ 75.4

Earnings Per Share - Reconcilia

Earnings Per Share - Reconciliation of Number of Common Stock used in Computing Basic and Diluted Earning Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Number Of Shares Outstanding [Abstract]
Weighted average shares outstanding - basic	117,737,180	120,414,218	122,885,346
Dilutive effect of share-based awards	756,023	195,381	144,326
Weighted average shares outstanding - diluted	118,493,203	120,609,599	123,029,672

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Millions		Oct. 30, 2012shares	Dec. 31, 2020USD ($)Installment$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / shares
Modified Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Phantom shares vested | shares			600,719
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of annual installments | Installment			3
Weighted Average Grant Date Fair Value Per, Granted			$ 149.38	$ 96.59	$ 91.85
Weighted average grant date fair value per, vested | $			$ 11.9	$ 7.3	$ 6.2
Unrecognized stock-based compensation cost | $			$ 9.9
Unrecognized compensation costs, weighted-average recognition periods			1 year 8 months 12 days
Phantom shares vested | shares			80,349
Unvested Weighted Average grant date fair value			$ 121.53	$ 90.65
PBRSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted Average Grant Date Fair Value Per, Granted	[1]		$ 146.29
Unrecognized stock-based compensation cost | $			$ 1.9
Unrecognized compensation costs, weighted-average recognition periods			2 years 1 month 6 days
Unvested Weighted Average grant date fair value			$ 146.29
Phantom Stock Plan [Member] | Modified Award [Member] | ASU 2017-09 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted Average Grant Date Fair Value Per, Granted				$ 120.41
Share based compensation outstanding number | shares				613,996
Vested Phantom Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted Average Grant Date Fair Value Per, Granted			120.56
Phantom Share Units (PSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares		1,500,000
Share-based compensation arrangement vesting increment percentage		20.00%
Share based compensation arrangement, employment period for eligibility of employees participation		10 years
Unvested Weighted Average grant date fair value			$ 113.65
Liability for unsettled stock awards | $			$ 0
Stock Incentive Plan 2016 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares			3,000,000
[1]	Amount represents PBRSUs granted at target. PBRSUs earned may range from zero to 200% of the target award. Actual PBRSUs earned for the 2020 performance period, as determined by the Compensation Committee, were equal to the target amount.

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Restricted Stock Award Activity for Employees and Non-Employee Directors (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted
Forfeited
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning Balance	163,723
Granted	75,638
Vested	(80,349)
Forfeited	(19,149)
Ending Balance	139,863	163,723
Weighted Average Grant Date Fair Value Per Share, Beginning Balance	$ 90.65
Weighted Average Grant Date Fair Value Per, Granted	149.38	$ 96.59	$ 91.85
Weighted Average Grant Date Fair Value Per , Vested	85.68
Weighted Average Grant Date Fair Value Per Share, Forfeited	117.86
Weighted Average Grant Date Fair Value Per Share, Ending Balance	$ 121.53	$ 90.65

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Activity for PBRSUs for Employees (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted
Forfeited
PBRSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted	31,072	[1]
Ending Balance	31,072
Weighted Average Grant Date Fair Value Per, Granted | $ / shares	$ 146.29	[1]
Weighted Average Grant Date Fair Value Per Share, Ending Balance | $ / shares	$ 146.29
[1]	Amount represents PBRSUs granted at target. PBRSUs earned may range from zero to 200% of the target award. Actual PBRSUs earned for the 2020 performance period, as determined by the Compensation Committee, were equal to the target amount.

Share-Based Compensation - Su_3

Share-Based Compensation - Summary of Activity for PBRSUs for Employees (Parenthetical) (Details) - PBRSUs [Member]	12 Months Ended
	Dec. 31, 2020
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grants as percentage of target award	0.00%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grants as percentage of target award	200.00%

Share-Based Compensation - Su_4

Share-Based Compensation - Summary of the Changes in the Number of Outstanding Phantom Stock Shares (Details)	12 Months Ended
	Dec. 31, 2020shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance of shares outstanding at December 31, 2019	718,861
Granted
Settled	(104,865)
Forfeited
Balance of shares outstanding at December 31, 2020	613,996
Employee Phantom Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance of shares outstanding at December 31, 2019	637,755
Granted
Settled	(104,865)
Forfeited
Balance of shares outstanding at December 31, 2020	532,890
Director Phantom Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance of shares outstanding at December 31, 2019	81,106
Granted
Settled
Forfeited
Balance of shares outstanding at December 31, 2020	81,106

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Short-term Investments (Details) $ in Thousands	Dec. 31, 2020USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	$ 330,274
U.S. government securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	125,379
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	125,379
Level 1 [Member] | U.S. government securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	125,379
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	204,895
Certificates of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	75,032
Certificates of deposit [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	75,032
Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	129,863
Commercial paper [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair value	$ 129,863

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Debt and capital lease obligations	$ 99,931	$ 45,000
Long-term debt, fair value	$ 105,400	$ 46,100

Schedule II - Valuation And Q_2

Schedule II - Valuation And Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation And Qualifying Accounts [Abstract]
Balance at Beginning of Period	$ 3,497	$ 3,632	$ 3,488
Charged to Costs and Expenses	3,248	2,113	3,846
Deductions	2,650	2,248	3,702
Balance at End of Period	$ 4,095	$ 3,497	$ 3,632