Knight-Swift Transportation (KNX) 10-Q 4 May 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	Apr. 27, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-35007
Entity Registrant Name	Knight-Swift Transportation Holdings Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-5589597
Entity Address, Address Line One	2002 West Wahalla Lane
Entity Address, City or Town	Phoenix
Entity Address, State or Province	AZ
Entity Address, Postal Zip Code	85027
City Area Code	602
Local Phone Number	269-2000
Title of 12(b) Security	Common Stock $0.01 Par Value
Trading Symbol	KNX
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		163,568,435
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001492691
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) shares in Thousands, $ in Thousands		Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents		$ 242,860	$ 261,001
Cash and cash equivalents – restricted	[1]	128,774	87,241
Restricted investments, held-to-maturity, amortized cost		8,302	5,866
Trade receivables, net of allowance for doubtful accounts of $19,883 and $21,663, respectively		939,704	911,336
Contract balance – revenue in transit		21,185	22,936
Prepaid expenses		86,742	90,507
Assets held for sale		11,421	8,166
Income tax receivable		217	909
Other current assets		27,064	26,318
Total current assets		1,466,269	1,414,280
Gross property and equipment		5,235,593	5,118,897
Less: accumulated depreciation and amortization		(1,655,908)	(1,563,533)
Property and equipment, net		3,579,685	3,555,364
Operating lease right-of-use-assets		141,363	147,540
Goodwill		3,518,589	3,515,135
Intangible assets, net		1,814,883	1,831,049
Other long-term assets		175,017	192,132
Total assets		10,695,806	10,655,500
Current liabilities:
Accounts payable		248,762	224,844
Accrued payroll and purchased transportation		237,909	217,084
Accrued liabilities		188,008	128,536
Claims accruals – current portion		223,382	206,607
Finance lease liabilities and long-term debt – current portion		234,146	262,423
Operating lease liabilities – current portion		33,822	35,322
Total current liabilities		1,166,029	1,074,816
Revolving line of credit		165,000	260,000
Long-term debt – less current portion		1,029,159	1,037,552
Finance lease liabilities – less current portion		277,839	256,166
Operating lease liabilities – less current portion		103,161	107,614
Accounts receivable securitization – less current portion		278,539	278,483
Claims accruals – less current portion		202,737	210,714
Deferred tax liabilities		881,287	874,877
Other long-term liabilities		11,112	11,828
Total liabilities		4,114,863	4,112,050
Commitments and contingencies (Notes 3, 7, 8, and 9)
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 10,000 shares authorized; none issued		$ 0	$ 0
Parenthetical - Preferred stock, par value (in dollars per share)		$ 0.01	$ 0.01
Parenthetical - Preferred stock, shares authorized (in shares)		10,000	10,000
Parenthetical - Preferred stock, shares issued (in shares)		0	0
Common stock, par value $0.01 per share; 500,000 shares authorized; 163,635 and 165,980 shares issued and outstanding as of March 31, 2022 and December 31, 2021, respectively.		$ 1,636	$ 1,660
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized (in shares)		500,000	500,000
Common stock, shares issued (in shares)		163,635	165,980
Common stock, shares outstanding (in shares)		163,635	165,980
Accumulated other comprehensive loss		$ (935)	$ (563)
Additional paid-in capital		4,360,889	4,350,913
Retained earnings		2,209,104	2,181,142
Total Knight-Swift stockholders' equity		6,570,694	6,533,152
Noncontrolling interest		10,249	10,298
Total stockholders’ equity		6,580,943	6,543,450
Total liabilities and stockholders’ equity		$ 10,695,806	$ 10,655,500
Common Class A [Member]
Stockholders’ equity:
Common stock, shares outstanding (in shares)		163,635	165,980
[1]	Reflects cash and cash equivalents that are primarily restricted for claims payments.

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Total revenue	$ 1,826,989	$ 1,223,014
Operating expenses:
Salaries, wages, and benefits	536,056	370,370
Fuel	190,489	118,236
Operations and maintenance	95,883	68,070
Insurance and claims	98,192	55,643
Operating taxes and licenses	29,037	22,048
Communications	5,870	5,037
Depreciation and amortization of property and equipment	145,044	119,915
Amortization of intangibles	16,166	11,749
Rental expense	13,401	16,864
Purchased transportation	386,446	258,230
Impairments	810	0
Miscellaneous operating expenses	11,509	14,593
Total operating expenses	1,528,903	1,060,755
Operating income	298,086	162,259
Other (expenses) income:
Interest income	461	294
Interest expense	(6,680)	(3,486)
Other (expense) income, net	(14,405)	16,105
Total other (expenses) income, net	(20,624)	12,913
Income before income taxes	277,462	175,172
Income tax expense	69,174	45,329
Net income	208,288	129,843
Net loss (income) attributable to noncontrolling interest	49	(53)
Net income attributable to Knight-Swift	208,337	129,790
Other comprehensive loss	(372)	0
Comprehensive income	$ 207,965	$ 129,790
Earnings per share:
Basic (in dollars per share)	$ 1.26	$ 0.77
Diluted (in dollars per share)	1.25	0.77
Dividends declared per share: (in dollars per share)	$ 0.12	$ 0.08
Weighted average shares outstanding:
Basic (in shares)	165,377	167,478
Diluted (in shares)	166,499	168,374
Revenue, excluding truckload and LTL fuel surcharge
Total revenue	$ 1,647,878	$ 1,133,105
Truckload and LTL fuel surcharge
Total revenue	$ 179,111	$ 89,909

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Cash Flows [Abstract]
Net income	$ 208,288	$ 129,843
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment, and intangibles	161,210	131,664
Gain on sale of property and equipment	(34,801)	(10,537)
Impairments	810	0
Deferred income taxes	4,246	(18,920)
Non-cash lease expense	9,490	15,589
Other adjustments to reconcile net income to net cash provided by operating activities	32,229	(6,522)
Increase (decrease) in cash resulting from changes in:
Trade receivables	(28,007)	(11,586)
Income tax receivable	692	2,872
Accounts payable	22,074	12,534
Accrued liabilities and claims accrual	89,289	70,975
Operating lease liabilities	(9,267)	(15,174)
Other assets and liabilities	607	5,375
Net cash provided by operating activities	456,860	306,113
Cash flows from investing activities:
Proceeds from maturities of held-to-maturity investments	1,881	500
Purchases of held-to-maturity investments	(4,372)	(512)
Proceeds from sale of property and equipment, including assets held for sale	60,532	67,175
Purchases of property and equipment	(164,974)	(111,020)
Expenditures on assets held for sale	(43)	(401)
Net cash, restricted cash, and equivalents invested in acquisitions	(1,291)	(39,281)
Other cash flows from investing activities	(1,920)	9,398
Net cash used in investing activities	(110,187)	(74,141)
Cash flows from financing activities:
Repayment of finance leases and long-term debt	(48,843)	(6,600)
Repayments on revolving lines of credit, net	(95,000)	(95,000)
Repayment of accounts receivable securitization	0	(15,000)
Proceeds from common stock issued	1,220	2,709
Repurchases of the Company's common stock	(144,881)	(53,661)
Dividends paid	(20,137)	(13,624)
Other cash flows from financing activities	(15,608)	(4,190)
Net cash used in financing activities	(323,249)	(185,366)
Net increase in cash, restricted cash, and equivalents	23,424	46,606
Cash, restricted cash, and equivalents at beginning of period	350,023	197,277
Cash, restricted cash, and equivalents at end of period	373,447	243,883
Cash paid during the period for:
Interest	5,928	2,505
Income taxes	1,778	2,199
Other Significant Noncash Transactions [Line Items]
Equipment acquired included in accounts payable	11,643	13,860
Purchase price adjustment on acquisition	2,163	0
Right-of-use assets obtained (forfeited) in exchange for operating lease liabilities	3,314	(2,608)
Financing provided to independent contractors for equipment sold [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities	1,536	462
Transfers from property and equipment to assets held for sale [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities	16,986	29,955
Noncontrolling Interest Associated With Acquisition
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities	0	10,281
Property and equipment obtained in exchange for finance lease liabilities from operating lease liabilities
Other Significant Noncash Transactions [Line Items]
Property and equipment obtained in exchange for finance lease liabilities reclassified from operating lease liabilities	0	28,149
Acquisitions [Member]
Other Significant Noncash Transactions [Line Items]
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 0
2021 Acquisitions
Other Significant Noncash Transactions [Line Items]
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		$ 560

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) Reconciliation of Cash, Restricted Cash, and Cash Equivalents - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Statement of Cash Flows [Abstract]
Cash and cash equivalents		$ 242,860	$ 261,001	$ 194,650	$ 156,699
Cash and cash equivalents – restricted	[1]	128,774	87,241	47,867	39,328
Other long-term assets	[1]	1,813	1,781	1,366	1,250
Cash, restricted cash, and equivalents		$ 373,447	$ 350,023	$ 243,883	$ 197,277
[1]	Reflects cash and cash equivalents that are primarily restricted for claims payments.

Condensed Consolidated Statem_4

Condensed Consolidated Statement Of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent	Total Knight-Swift Equity [Member]	Noncontrolling Interest [Member]	Common Class A [Member]	Common Class A [Member]Common Stock
Beginning balance, shares at Dec. 31, 2020							166,553
Beginning balance, value at Dec. 31, 2020	$ 5,872,040	$ 4,301,424	$ 1,566,759	$ 0	$ 5,869,848	$ 2,192		$ 1,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued to employees (Shares)							220
Common stock issued to employees	2,009	2,006			2,009			3
Common stock issued under ESPP (Shares)							18
Common stock issued under ESPP	700	700			700			0
Company shares repurchased (Shares)							(1,303)
Company shares repurchased	(53,661)		(53,648)		(53,661)			(13)
Shares withheld – RSU settlement	(4,159)		(4,159)		(4,159)
Employee stock-based compensation expense	$ 5,662	5,662			5,662
Dividends declared per share: (in dollars per share)	$ 0.08
Cash dividends paid and dividends accrued	$ (13,345)		(13,345)		(13,345)
Net income attributable to Knight-Swift	129,790		129,790		129,790
Investment in noncontrolling interest	10,281					10,281
Distribution to noncontrolling interest	(32)					(32)
Net loss (income) attributable to noncontrolling interest	53					53
Ending balance, shares at Mar. 31, 2021							165,488
Ending balance, value at Mar. 31, 2021	$ 5,949,338	4,309,792	1,625,397	0	5,936,844	12,494		1,655
Beginning balance, shares at Dec. 31, 2021	165,980						165,980
Beginning balance, value at Dec. 31, 2021	$ 6,543,450	4,350,913	2,181,142	(563)	6,533,152	10,298		1,660
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued to employees (Shares)							364
Common stock issued to employees	411	408			411			3
Common stock issued under ESPP (Shares)							14
Common stock issued under ESPP	809	809			809			0
Company shares repurchased (Shares)							(2,723)
Company shares repurchased	(144,881)		(144,854)		(144,881)			(27)
Shares withheld – RSU settlement	(15,608)		(15,608)		(15,608)
Employee stock-based compensation expense	$ 8,759	8,759			8,759
Dividends declared per share: (in dollars per share)	$ 0.12
Cash dividends paid and dividends accrued	$ (19,913)		(19,913)		(19,913)
Net income attributable to Knight-Swift	208,337		208,337		208,337
Other comprehensive loss	(372)			(372)	(372)
Net loss (income) attributable to noncontrolling interest	$ (49)					(49)
Ending balance, shares at Mar. 31, 2022	163,635						163,635
Ending balance, value at Mar. 31, 2022	$ 6,580,943	$ 4,360,889	$ 2,209,104	$ (935)	$ 6,570,694	$ 10,249		$ 1,636

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited)(Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Receivables [Abstract]
Parenthetical - allowance for doubtful accounts	$ 19,883	$ 21,663

Introduction and Basis of Prese

Introduction and Basis of Presentation	3 Months Ended
	Mar. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Introduction and Basis of Presentation	Introduction and Basis of Presentation Certain acronyms and terms used throughout this Quarterly Report are specific to the Company, commonly used in the trucking industry, or are otherwise frequently used throughout this document. Definitions for these acronyms and terms are provided in the "Glossary of Terms," available in the front of this document. Description of Business Knight-Swift is a transportation solutions provider, headquartered in Phoenix, Arizona. During the first quarter of 2022, the Company operated an average of 17,965 tractors (comprised of 16,159 company tractors and 1,806 independent contractor tractors) and 71,310 trailers within the Truckload segment and leasing activities within the non-reportable segments. The LTL segment operated an average of 3,091 tractors and 8,302 trailers. Additionally, the Intermodal segment operated an average of 584 tractors and 11,027 intermodal containers. As of March 31, 2022 , the Company's four reportable segments were Truckload, Logistics, LTL, and Intermodal. Basis of Presentation The condensed consolidated financial statements and footnotes included in this Quarterly Report include the accounts of Knight-Swift Transportation Holdings Inc. and its subsidiaries and should be read in conjunction with the consolidated financial statements and footnotes included in Knight-Swift's 2021 Annual Report. In management's opinion, these condensed consolidated financial statements were prepared in accordance with GAAP and include all adjustments necessary (consisting of normal recurring adjustments) for the fair statement of the periods presented. With respect to transactional/durational data, references to years pertain to calendar years. Similarly, references to quarters pertain to calendar quarters. 2021 Acquisitions The Company recently acquired the following entities: • 100.0% of MME on December 6, 2021. The results are included within the LTL segment. • 100.0% of ACT on July 5, 2021. The results are included within the LTL segment. • 100.0% of UTXL on June 1, 2021. The results are included within the Logistics segment. • 79.44% of Eleos on February 1, 2021. The results are included within the non-reportable segments. The noncontrolling interest is presented as a separate component of the condensed consolidated financial statements. Note regarding comparability: In accordance with the accounting treatment applicable to the transactions, the Company's consolidated results, as reported, do not include the operating results of its ownership interest in the acquired entities prior to the respective acquisition dates. Accordingly, comparisons between the Company's current and prior period results may not be meaningful. Additional information regarding the Company's recent acquisitions is included in Note 3. Seasonality In the truckload transportation industry, results of operations generally follow a seasonal pattern. Freight volumes in the first quarter are typically lower due to less consumer demand, customers reducing shipments following the holiday season, and inclement weather, while operating expenses generally increase. Tractor productivity of the Company's Truckload fleet, third-party carriers, and independent contractors decreases during the winter months due to decreased fuel efficiency, increased cold weather-related equipment maintenance and repairs, and increased insurance claims and costs attributed to higher accident frequency from harsh weather. These factors typically lead to lower operating profitability, as compared to other parts of the year. Additionally, beginning in the latter half of the

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	3 Months Ended
	Mar. 31, 2022
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Date Issued Reference Description Expected Adoption Date and Method Financial Statement Impact March 2022 ASU No. 2022-02: Financial Instruments – Credit Losses (ASC 326), Troubled Debt Restructurings and Vintage Disclosures The amendments in this ASU require that a creditor incorporates troubled debt restructurings into the allowance for credit losses and disclose current-period gross writeoffs by year of origination for financing receivables and net investments in leases. January 2023, Prospective Currently under evaluation, but not expected to be material

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2022
Business Combinations [Abstract]
Acquisitions	Acquisitions First quarter 2022 developments related to the Company's recent acquisitions are discussed below. MME On December 6, 2021, the Company, through a wholly owned subsidiary, acquired 100.0% of Bismarck, North Dakota-based MME. MME provides LTL, full truckload, and specialized and other logistics transportation services to a diverse customer base in its service territory in the upper Midwestern and great Northwestern regions of the US. During the measurement period, the net working capital adjustment increased by $1.3 million based on the actual versus estimated net working capital adjustment as of the transaction date. This adjustment resulted in increasing the total purchase price consideration to $165.7 million. The Company reduced the deferred tax liabilities on MME's opening balance sheet by $2.2 million based on valuation of the Company's intangible assets. These measurement period adjustments resulted a $3.5 million increase in goodwill related to the MME acquisition. ACT On July 5, 2021, the Company acquired 100% of Dothan, Alabama-based ACT. ACT is a leading LTL carrier that also offers dedicated contract carriage and ancillary services. During the quarter ended March 31, 2022, the Company's condensed consolidated operating results included ACT's total revenue of $217.7 million and net income of $16.1 million. ACT's net income during the quarter ended March 31, 2022 included $3.5 million related to the amortization of intangible assets acquired in the ACT Acquisition. Pro Forma Information (Unaudited) — The following unaudited pro forma information combines the historical operations of the Company and ACT giving effect to the ACT Acquisition, and related transactions as if consummated on January 1, 2020. Quarter Ended March 31, 2021 (in thousands, except per share data) Total revenue $ 1,412,232 Net income attributable to Knight-Swift 139,189 Earnings per share – diluted 0.83 The unaudited pro forma condensed combined financial information has been presented for comparative purposes only and includes certain adjustments such as recognition of assets acquired at estimated fair values and related depreciation and amortization, elimination of transaction costs incurred by Knight-Swift and ACT during the periods presented that were directly related to the ACT Acquisition, and related income tax effects of these items. The unaudited pro forma condensed combined financial information does not purport to represent the actual results of operations that Knight-Swift and ACT would have achieved had the companies been combined during the periods presented in the unaudited pro forma condensed combined financial statements and is not intended to project the future results of operations that the combined company may achieve after the identified transactions. The unaudited pro forma condensed combined financial information does not reflect any cost savings that may be realized as a result of the ACT Acquisition and also does not reflect any restructuring or integration-related costs to achieve those potential cost savings. UTXL On June 1, 2021, pursuant to a stock purchase agreement, the Company, through a wholly owned subsidiary, acquired 100.0% of the equity interests of UTXL, a premier third-party logistics company which specializes in over-the-road full truckload and multi-stop loads. As of March 31, 2022, contingent consideration associated with the transaction was $2.5 million included in "Accrued liabilities" and $2.5 million included in "Other long-term liabilities" in the Company's condensed consolidated balance sheets, depending on the expected payment dates. Eleos On February 1, 2021, pursuant to a membership interest purchase agreement ("MIPA"), the Company, through a wholly owned subsidiary, acquired 79.44% of the issued and outstanding membership interests of Eleos Technologies, LLC ("Eleos"), a Greenville, South Carolina-based software provider, specializing in mobile driving platforms, which complement the Company's suite of services. The purchase price was allocated based on estimated fair values of the assets acquired and liabilities assumed at the acquisition date. The purchase price allocation was open for adjustments through the end of the measurement period, which closed one year from the February 1, 2021 acquisition date. Purchase Price Allocations Unless otherwise stated, the purchase price allocations for the above acquisitions are preliminary and have been allocated based on estimated fair values of the assets acquired and liabilities assumed at the acquisition date, and among other things may be pending the completion of the valuation of acquired tangible assets, an independent valuation of certain acquired intangible assets, assessment of lease agreements, assessment of certain liabilities, the calculation of deferred taxes based upon the underlying tax basis of assets acquired and liabilities assumed, and assessment of other tax related items as applicable. As the Company obtains more information, the preliminary purchase price allocations disclosed below are subject to change. Any future adjustments to the preliminary purchase price allocations, including changes within identifiable intangible assets or estimation uncertainty impacted by market conditions, may impact future net earnings. The purchase price allocation adjustments can be made through the end of the measurement periods, which is not to exceed one year from the respective acquisition dates.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effective Tax Rate — The quarter-to-date March 31, 2022 and March 31, 2021 effective tax rates were 24.9% and 25.9%, respectively. Valuation Allowance — The Company has not established a valuation allowance as it has been determined that, based upon available evidence, a valuation allowance is not required. Management believes that it is more likely than not that the results of future operations will generate sufficient taxable income to realize the deferred tax assets. Unrecognized Tax Benefits — Management believes it is reasonably possible that a decrease of up to $0.3 million in unrecognized tax benefits relating to federal deductions may be necessary within the next twelve months. Interest and Penalties — Accrued interest and penalties related to unrecognized tax benefits were approximately $0.1 million as of March 31, 2022 and December 31, 2021. Tax Examinations — Certain of the Company's subsidiaries are currently under examination by Federal and various state jurisdictions for tax years ranging from 2014 to 2020 . At the completion of these examinations, management does not expect any adjustments that would have a material impact on the Company's effective tax rate. Years subsequent to 2017 remain subject to examination.

Accounts Receivable Securitizat

Accounts Receivable Securitization	3 Months Ended
	Mar. 31, 2022
Transfers and Servicing [Abstract]
Accounts Receivable Securitization	Accounts Receivable Securitization As of March 31, 2022, the Company's eligible receivables related to the 2021 RSA generally have high credit quality, as determined by the obligor's corporate credit rating. The 2021 RSA is subject to fees, various affirmative and negative covenants, representations and warranties, and default and termination provisions customary for facilities of this type. The Company was in compliance with these covenants as of March 31, 2022. Collections on the underlying receivables by the Company are held for the benefit of SRCII and the various purchasers and are unavailable to satisfy claims of the Company and its subsidiaries. The following table summarizes the key terms of the 2021 RSA (dollars in thousands): Effective date April 23, 2021 Final maturity date April 23, 2024 Borrowing capacity $400,000 Accordion option 1 $100,000 Unused commitment fee rate 2 20 to 40 basis points Program fees on outstanding balances 3 one-month LIBOR + 82.5 basis points 1 The accordion option increases the maximum borrowing capacity, subject to participation of the purchasers. 2 The 2021 RSA commitment fees rate are based on the percentage of the maximum borrowing capacity utilized. 3 As identified within the 2021 RSA, the lender can trigger an amendment by identifying and deciding upon a replacement for LIBOR. Availability under the 2021 RSA is calculated as follows: March 31, 2022 December 31, 2021 (In thousands) Borrowing base, based on eligible receivables $ 400,000 $ 400,000 Less: outstanding borrowings 1 (279,000) (279,000) Less: outstanding letters of credit, net (65,300) (65,300) Availability under accounts receivable securitization facilities $ 55,700 $ 55,700 1 As of March 31, 2022 and December 31, 2021, outstanding borrowings are included in "Accounts receivable securitization – less current portion" in the condensed consolidated balance sheets and are offset by $0.5 million of deferred loan costs. Interest accrued on the aggregate principal balance at a rate of 1.1% and 0.9% as of March 31, 2022 and December 31, 2021, respectively.

Debt And Financing

Debt And Financing	3 Months Ended
	Mar. 31, 2022
Debt Disclosure [Abstract]
Debt and Financing	Debt and Financing Other than the Company's accounts receivable securitization as discussed in Note 5, the Company's long-term debt consisted of the following: March 31, 2022 December 31, 2021 (In thousands) 2021 Term Loan A-1, due December 3, 2022, net 1 2 $ 169,765 $ 199,676 2021 Term Loan A-2, due September 3, 2024, net 1 2 199,645 199,607 2021 Term Loan A-3, due September 3, 2026, net 1 2 798,440 798,352 2021 Prudential Notes, net 1 39,261 47,265 Other 4,567 5,069 Total long-term debt, including current portion 1,211,678 1,249,969 Less: current portion of long-term debt (182,519) (212,417) Long-term debt, less current portion $ 1,029,159 $ 1,037,552 March 31, 2022 December 31, 2021 (In thousands) Total long-term debt, including current portion $ 1,211,678 $ 1,249,969 2021 Revolver, due September 3, 2026 1 3 165,000 260,000 Long-term debt, including revolving line of credit $ 1,376,678 $ 1,509,969 1 Refer to Note 12 for information regarding the fair value of debt. 2 The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.2 million, $0.4 million, and $1.6 million in deferred loan costs as of March 31, 2022, respectively. The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 3 The Company also had outstanding letters of credit of $64.4 million and $64.0 million under the 2021 Revolver, primarily related to workers' compensation and self-insurance liabilities at March 31, 2022 and December 31, 2021, respectively. Credit Agreements 2021 Debt Agreement — On September 3, 2021, the Company entered into the $2.3 billion 2021 Debt Agreement (an unsecured credit facility), with a group of banks, replacing the 2017 Debt Agreement and the July 2021 Term Loan. The following table presents the key terms of the 2021 Debt Agreement: 2021 Term Loan A-1 2021 Term Loan A-2 2021 Term Loan A-3 2021 Revolver 2 2021 Debt Agreement Terms (Dollars in thousands) Maximum borrowing capacity $200,000 $200,000 $800,000 $1,100,000 Final maturity date December 3, 2022 September 3, 2024 September 3, 2026 September 3, 2026 Interest rate minimum margin BSBY BSBY BSBY BSBY Interest rate minimum margin 1 0.75% 0.75% 0.88% 0.88% Interest rate maximum margin 1 1.38% 1.38% 1.50% 1.50% Minimum principal payment — amount $— $— $10,000 $— Minimum principal payment — frequency Once Once Quarterly Once Minimum principal payment — commencement date December 3, 2022 September 3, 2024 September 30, 2024 September 3, 2026 1 The interest rate margin for the 2021 Term Loans and 2021 Revolver is based on the Company's consolidated leverage ratio. As of March 31, 2022, interest accrued at 1.08% on the 2021 Term Loans and 1.13% on the 2021 Revolver. 2 The commitment fee for the unused portion of the 2021 Revolver is based on the Company's consolidated leverage ratio, and ranges from 0.1% to 0.2%. As of March 31, 2022, commitment fees on the unused portion of the 2021 Revolver accrued at 0.1% and outstanding letter of credit fees accrued at 1.0%. Pursuant to the 2021 Debt Agreement, the 2021 Revolver and the 2021 Term Loans contain certain financial covenants with respect to a maximum net leverage ratio and a minimum consolidated interest coverage ratio. The 2021 Debt Agreement provides flexibility regarding the use of proceeds from asset sales, payment of dividends, stock repurchases, and equipment financing. In addition to the financial covenants, the 2021 Debt Agreement includes usual and customary events of default for a facility of this nature and provides that, upon the occurrence and continuation of an event of default, payment of all amounts payable under the 2021 Debt Agreement may be accelerated, and the lenders' commitments may be terminated. The 2021 Debt Agreement contains certain usual and customary restrictions and covenants relating to, among other things, dividends (which are restricted only if a default or event of default occurs and is continuing or would result therefrom), liens, affiliate transactions, and other indebtedness. As of March 31, 2022, the Company was in compliance with the covenants under the 2021 Debt Agreement. Borrowings under the 2021 Debt Agreement, are made by Knight-Swift Transportation Holdings Inc., and are guaranteed by certain of the Company's domestic subsidiaries (other than its captive insurance subsidiaries, driving academy subsidiary, and bankruptcy-remote special purpose subsidiary). ACT Credit Agreement Prudential Notes — The 2021 Prudential Notes allow ACT to borrow up to $125.0 million, less amounts then currently outstanding with Prudential Capital Group, provided that certain financial ratios are maintained. The 2021 Prudential Notes have interest rates ranging fro m 4.05% to 4.40% a nd various maturity dates ranging from October 2023 through January 2028. The 2021 Prudential Notes are unsecured and contain usual and customary restrictions on, among other things, the ability to make certain payments to stockholders, similar to the provisions of the Company's 2021 Debt Agreement. As of March 31, 2022 , ACT had $87.9 million available under the agreement. See Note 12 for fair value disclosures regarding the Company's debt instruments.

Defined Benefit Pension Plan

Defined Benefit Pension Plan	3 Months Ended
	Mar. 31, 2022
Retirement Benefits [Abstract]
Defined Benefit Pension Plan	Defined Benefit Pension Plan Net periodic pension income and benefits paid during the first quarter of 2022 were immaterial. Assumptions A weighted-average discount rate of 3.38% was used to determine benefit obligations as of March 31, 2022. The following weighted-average assumptions were used to determine net periodic pension cost: Quarter Ended March 31, 2022 Discount rate 2.55 % Expected long-term rate of return on pension plan assets 6.00 % Refer to Note 12 for additional information regarding fair value measurements of the Company's investments.

Commitments

Commitments	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments	Commitments Purchase Commitments As of March 31, 2022, the Company had outstanding commitments to purchase revenue equipment of $682.2 million in the remainder of 2022 ($479.3 million of which were tractor commitments), $58.6 million in 2023 ($50.4 million of which were tractor commitments), and none thereafter. These purchases may be financed through any combination of finance leases, operating leases, debt, proceeds from sales of existing equipment, and cash flows from operations. As of March 31, 2022, the Company had outstanding commitments to purchase facilities and non-revenue equipment of $52.0 million in the remainder of 2022, $6.4 million from 2023 through 2024, $1.2 million from 2025 through 2026, and none thereafter. Factors such as costs and opportunities for future terminal expansions may change the amount of such expenditures.

Contingencies and Legal Proceed

Contingencies and Legal Proceedings	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Legal Proceedings	Contingencies and Legal Proceedings Legal Proceedings Information is provided below regarding the nature, status, and contingent loss amounts, if any, associated with the Company's pending legal matters. There are inherent uncertainties in these legal matters, some of which are beyond management's control, making the ultimate outcomes difficult to predict. Moreover, management's views and estimates related to these matters may change in the future, as new events and circumstances arise and the matters continue to develop. The Company has made accruals with respect to its legal matters where appropriate, which are included in "Accrued liabilities" in the condensed consolidated balance sheets. The Company has recorded an aggregate accrual of approximately $18.6 million, relating to the Company's outstanding legal proceedings as of March 31, 2022. Based on management's present knowledge of the facts and (in certain cases) advice of outside counsel, management does not believe that loss contingencies arising from pending matters are likely to have a material adverse effect on the Company's overall financial position, operating results, or cash flows after taking into account any existing accruals. However, actual outcomes could be material to the Company's financial position, operating results, or cash flows for any particular period. EMPLOYEE COMPENSATION AND PAY PRACTICES MATTERS California Wage, Meal, and Rest Class Actions The plaintiffs generally allege one or more of the following: that the Company 1) failed to pay the California minimum wage; 2) failed to provide proper meal and rest periods; 3) failed to timely pay wages upon separation from employment; 4) failed to pay for all hours worked; 5) failed to pay overtime; 6) failed to properly reimburse work-related expenses; and 7) failed to provide accurate wage statements. Plaintiff(s) Defendant(s) Date instituted Court or agency currently pending in John Burnell 1 Swift Transportation Co., Inc March 22, 2010 United States District Court for the Central District of California James R. Rudsell 1 Swift Transportation Co. of Arizona, LLC and Swift Transportation Company April 5, 2012 United States District Court for the Central District of California Recent Developments and Current Status In April 2019, the parties reached settlement of this matter. In January 2020, the court granted final approval of the settlement. Two objectors appealed the court’s decision granting final approval of the settlement. The likelihood that a loss has been incurred is probable and estimable, and the loss has accordingly been accrued as of March 31, 2022. INDEPENDENT CONTRACTOR MATTERS Ninth Circuit Independent Contractor Misclassification Class Action The putative class alleges that Swift misclassified independent contractors as independent contractors, instead of employees, in violation of the Fair Labor Standards Act and various state laws. The lawsuit also raises certain related issues with respect to the lease agreements that certain independent contractors have entered into with Interstate Equipment Leasing, LLC. The putative class seeks unpaid wages, liquidated damages, interest, other costs, and attorneys' fees. Plaintiff(s) Defendant(s) Date instituted Court or agency currently pending in Joseph Sheer, Virginia Van Dusen, Jose Motolinia, Vickii Schwalm, Peter Wood 1 Swift Transportation Co., Inc., Interstate Equipment Leasing, Inc., Jerry Moyes, and Chad Killebrew December 22, 2009 United States District Court of Arizona and Ninth Circuit Court of Appeals Recent Developments and Current Status In January 2020, the court granted final approval of the settlement in this matter. In March 2020, the Company paid the settlement amount approved by the court. As of March 31, 2022, the Company has accrued for anticipated costs associated with finalizing this matter. 1 Individually and on behalf of all others similarly situated. Self Insurance Effective March 1, 2022, ACT retains a $10.0 million self-insured retention per occurrence, as compared to $2.0 million per occurrence with a $5.0 million annual corridor deductible subject to a $10.0 million three-year policy term aggregate cap during the previous policy period. This was the only material change related to our self insurance policies during the first quarter of 2022.

Share Repurchase Plans

Share Repurchase Plans	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Share Repurchase Plan	Share Repurchase Plans 2020 Knight-Swift Share Repurchase Plan On November 30, 2020, the Company announced that the Board approved the repurchase of up to $250.0 million worth of the Company's outstanding common stock (the "2020 Knight-Swift Share Repurchase Plan"). The following table presents the Company's repurchases of its common stock under the respective share repurchase plans, excluding advisory fees: Share Repurchase Plan Quarter Ended March 31, 2022 Quarter Ended March 31, 2021 Board Approval Date Authorized Amount Shares Amount Shares Amount (shares and dollars in thousands) November 24, 2020 1 $250,000 2,723 $ 144,881 1,303 $ 53,661 1 $47.9 million and $192.8 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of March 31, 2022 and December 31, 2021, respectively. Subsequent to March 31, 2022, the Company repurchased 0.1 million shares for $5.1 million under the 2020 Knight-Swift Share Repurchase Plan. 2022 Knight-Swift Share Repurchase Plan On April 25, 2022, the Company announced that the Board approved the repurchase of up to $350.0 million of the Company's outstanding common stock (the "2022 Knight-Swift Share Repurchase Plan"). With the adoption of the 2022 Knight-Swift Share Repurchase Plan, the Company terminated the 2020 Knight-Swift Share Repurchase Plan, which had approximately $42.8 million of authorized purchases remaining upon termination. Subsequent to March 31, 2022, the Company repurchased 0.4 million shares for $17.3 million under the 2022 Knight-Swift Share Repurchase Plan, leaving $332.7 million available as of May 4, 2022.

Weighted Average Shares Outstan

Weighted Average Shares Outstanding	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Weighted Average Shares Outstanding	Weighted Average Shares Outstanding Earnings per share, basic and diluted, as presented in the condensed consolidated statements of comprehensive income, are calculated by dividing net income attributable to Knight-Swift by the respective weighted average common shares outstanding during the period. The following table reconciles basic weighted average shares outstanding to diluted weighted average shares outstanding: Quarter Ended March 31, 2022 2021 (In thousands) Basic weighted average common shares outstanding 165,377 167,478 Dilutive effect of equity awards 1,122 896 Diluted weighted average common shares outstanding 166,499 168,374 Anti-dilutive shares excluded from diluted earnings per share 1 239 6 1 Shares were excluded from the dilutive-effect calculation because the outstanding awards' exercise prices were greater than the average market price of the Company's common stock for the periods presented.

Fair Value Measurement

Fair Value Measurement	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement The following table presents the carrying amounts and estimated fair values of the Company's major categories of financial assets and liabilities: March 31, 2022 December 31, 2021 Condensed Consolidated Balance Sheets Caption Carrying Estimated Carrying Estimated (In thousands) Financial Assets: Equity method investments Other long-term assets 78,750 78,750 75,769 75,769 Investments in equity securities Other long-term assets 53,352 53,352 74,201 74,201 Convertible note Other current assets 10,437 10,437 10,141 10,141 Financial Liabilities: 2021 Term Loan A-1, due December 2022 1 Finance lease liabilities and long-term debt 169,765 170,000 199,676 200,000 2021 Term Loan A-2, due September 2024 1 Long-term debt – less current portion 199,645 200,000 199,607 200,000 2021 Term Loan A-3, due September 2026 1 Long-term debt – less current portion 798,440 800,000 798,352 800,000 2021 Revolver, due September 2026 Revolving line of credit 165,000 165,000 260,000 260,000 2021 Prudential Notes 2 Finance lease liabilities and long-term debt 39,261 39,341 47,265 47,354 2021 RSA, due April 2024 3 Accounts receivable securitization 278,539 279,000 278,483 279,000 Contingent consideration, acquisitions Accrued liabilities, Other long-term liabilities 13,100 13,100 13,100 13,100 1 The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.2 million, $0.4 million, and $1.6 million in deferred loan costs as of March 31, 2022, respectively. The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 2 The carrying amount of the 2021 Prudential Notes is net of $0.1 million in deferred loan costs as of March 31, 2022 and December 31, 2021 . T he carrying amount of the 2021 Prudential Notes is net of $2.2 million and $2.4 million in fair value adjustments as of March 31, 2022 and December 31, 2021 , respectively. 3 The carrying amount of the 2021 RSA is net of $0.5 million in deferred loan costs as of March 31, 2022 and December 31, 2021 . Recurring Fair Value Measurements (Assets) — The following table depicts the level in the fair value hierarchy of the inputs used to estimate the fair value of assets measured on a recurring basis as of March 31, 2022 and December 31, 2021 : Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs Unrealized Gain (Loss) Position (In thousands) As of March 31, 2022 Convertible note 1 $ 10,437 $ — $ — $ 10,437 $ 296 Investments in equity securities 2 53,352 53,352 — — (7,817) As of December 31, 2021 Convertible note 1 10,141 — — 10,141 141 Investments in equity securities 2 74,201 74,201 — — 14,456 1 The Company recognized $0.3 million of unrealized gains on the convertible note for the quarter ended March 31, 2022, which is included within "Other (expense) income, net" within the condensed consolidated statement of comprehensive income. No gain was recognized on the convertible note for the quarter ended March 31, 2021. The fair value of the note was determined using a discounted cash flow analysis based on the probability of exit event options and exit event dates. 2 Fair value activity from the investments in equity securities is recorded in "Other (expense) income, net" within the condensed consolidated statement of comprehensive income. During the quarter ended March 31, 2022, the Company recognized $20.8 million in losses on these investments in equity securities, consisting of $20.8 million in unrealized losses and no realized loss. During the quarter ended March 31, 2021, the Company recognized $10.4 million in gains, consisting of $6.9 million in unrealized gains and $3.5 million in realized gains. Embark Investment — As of March 31, 2022, the fair value of the combined investment in Embark was $37.0 million, resulting in a net unrealized loss of $17.5 million recognized during the quarter ended March 31, 2022 in "Operating (expense) income, net" in the condensed consolidated statements of comprehensive income. Recurring Fair Value Measurements (Liabilities) — The following table depicts the level in the fair value hierarchy of the inputs used to estimate the fair value of liabilities measured on a recurring basis as of March 31, 2022 and December 31, 2021: Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Gain (Loss) (In thousands) As of March 31, 2022 Contingent consideration associated with acquisitions 1 $ 13,100 $ — $ — $ 13,100 $ — As of December 31, 2021 Contingent consideration associated with acquisition 1 13,100 — — 13,100 — 1 The Company did not recognize any gains (losses) during the quarters ended March 31, 2022 and 2021 related to the revaluation of these liabilities. Refer to Note 3 for information regarding the components of these liabilities. Nonrecurring Fair Value Measurements (Assets) — The following table depicts the level in the fair value hierarchy of the inputs used to estimate fair value of assets measured on a nonrecurring basis as of March 31, 2022 and December 31, 2021: Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Loss (In thousands) As of March 31, 2022 Buildings 1 $ — $ — $ — $ — $ (810) As of December 31, 2021 Equipment 2 — — — — (299) 1 Reflects the non-cash impairment of building improvements (within the non-reportable segments). 2 Reflects the non-cash impairment of certain revenue equipment held for sale (within the non-reportable segments and the Truckload segment). Gain on Sale of Revenue Equipment — Net gains on disposals, including disposals of property and equipment classified as assets held for sale, reported in "Miscellaneous operating expenses" in the condensed consolidated statements of comprehensive income, were $34.8 million and $10.5 million for the quarters ended March 31, 2022 and 2021, respectively. The increase in net gains on disposals was primarily due to a stronger market for used revenue equipment during the quarter ended March 31, 2022, as compared to the same period in 2021. Nonrecurring Fair Value Measurements (Liabilities) — As of March 31, 2022 and December 31, 2021, the Company had no major categories of liabilities estimated at fair value that were measured on a nonrecurring basis. Fair Value of Pension Plan Assets — The following table sets forth by level the fair value hierarchy of ACT's pension plan financial assets accounted for at fair value on a recurring basis. Assets are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. ACT's assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of fair value assets and their placement within the fair value hierarchy levels. Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs (In thousands) As of March 31, 2022 US equity funds $ 14,442 $ 14,442 $ — $ — International equity funds 5,902 5,902 — — Fixed income funds 42,431 42,431 — — Cash and cash equivalents 1,418 1,418 — — Total pension plan assets $ 64,193 $ 64,193 $ — $ — As of December 31, 2021 US equity funds $ 14,877 $ 14,877 $ — $ — International equity funds 6,304 6,304 — — Fixed income funds 47,873 47,873 — — Cash and cash equivalents 1,413 1,413 — — Total pension plan assets $ 70,467 $ 70,467 $ — $ —

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2022
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Quarter Ended March 31, 2022 2021 Provided by Knight-Swift Received by Knight-Swift Provided by Knight-Swift Received by Knight-Swift (In thousands) Facility and Equipment Leases: Certain affiliates 1 — 78 — 57 Total $ — $ 78 $ — $ 57 Other Services: Certain affiliates 1 5 9 6 9 Total $ 5 $ 9 $ 6 $ 9 March 31, 2022 December 31, 2021 Receivable Payable Receivable Payable (In thousands) Certain affiliates 1 2 39 14 44 Total $ 2 $ 39 $ 14 $ 44 1 "Certain affiliates" includes entities that are associated with various board members and executives and require approval by the Board prior to completing transactions. Transactions with these entities generally include freight services, facility and equipment leases, equipment sales, and other services.

Information by Segment and Geog

Information by Segment and Geography	3 Months Ended
	Mar. 31, 2022
Segment Reporting [Abstract]
Information by Segment and Geography	Financial Information by Segment and Geography Segment Information Quarter Ended March 31, 2022 2021 Revenue: (In thousands) Truckload $ 1,080,531 $ 962,947 Logistics 282,039 118,887 LTL 255,125 — Intermodal 109,222 107,066 Subtotal $ 1,726,917 $ 1,188,900 Non-reportable segments 117,639 50,669 Intersegment eliminations (17,567) (16,555) Total revenue $ 1,826,989 $ 1,223,014 Quarter Ended March 31, 2022 2021 Operating income (loss): (In thousands) Truckload $ 205,117 $ 158,483 Logistics 39,601 7,577 LTL 26,377 — Intermodal 15,170 3,457 Subtotal $ 286,265 $ 169,517 Non-reportable segments 11,821 (7,258) Operating income $ 298,086 $ 162,259 Quarter Ended March 31, 2022 2021 Depreciation and amortization of property and equipment: (In thousands) Truckload $ 110,349 $ 101,885 Logistics 596 208 LTL 15,260 — Intermodal 3,864 3,818 Subtotal $ 130,069 $ 105,911 Non-reportable segments 14,975 14,004 Depreciation and amortization of property and equipment $ 145,044 $ 119,915 Geographical Information In the aggregate, total revenue from the Company's international operations was less than 5.0% of consolidated total revenue for the quarters ended March 31, 2022 and 2021. Additionally, long-lived assets on the Company's international subsidiary balance sheets were less than 5.0% of consolidated total assets as of March 31, 2022 and December 31, 2021.

Introduction and Basis of Pre_2

Introduction and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	In management's opinion, these condensed consolidated financial statements were prepared in accordance with GAAP and include all adjustments necessary (consisting of normal recurring adjustments) for the fair statement of the periods presented.

Recently Issued Accounting Pr_2

Recently Issued Accounting Pronouncements (Tables)	3 Months Ended
	Mar. 31, 2022
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recently Issued Accounting Pronouncements	Date Issued Reference Description Expected Adoption Date and Method Financial Statement Impact March 2022 ASU No. 2022-02: Financial Instruments – Credit Losses (ASC 326), Troubled Debt Restructurings and Vintage Disclosures The amendments in this ASU require that a creditor incorporates troubled debt restructurings into the allowance for credit losses and disclose current-period gross writeoffs by year of origination for financing receivables and net investments in leases. January 2023, Prospective Currently under evaluation, but not expected to be material

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2022
Business Combinations [Abstract]
Business Acquisition, Pro Forma Information	The following unaudited pro forma information combines the historical operations of the Company and ACT giving effect to the ACT Acquisition, and related transactions as if consummated on January 1, 2020. Quarter Ended March 31, 2021 (in thousands, except per share data) Total revenue $ 1,412,232 Net income attributable to Knight-Swift 139,189 Earnings per share – diluted 0.83

Accounts Receivable Securitiz_2

Accounts Receivable Securitization (Tables)	3 Months Ended
	Mar. 31, 2022
Transfers and Servicing [Abstract]
Schedule of Servicing Liabilities at Fair Value [Table Text Block]	The following table summarizes the key terms of the 2021 RSA (dollars in thousands): Effective date April 23, 2021 Final maturity date April 23, 2024 Borrowing capacity $400,000 Accordion option 1 $100,000 Unused commitment fee rate 2 20 to 40 basis points Program fees on outstanding balances 3 one-month LIBOR + 82.5 basis points 1 The accordion option increases the maximum borrowing capacity, subject to participation of the purchasers. 2 The 2021 RSA commitment fees rate are based on the percentage of the maximum borrowing capacity utilized. 3 As identified within the 2021 RSA, the lender can trigger an amendment by identifying and deciding upon a replacement for LIBOR. Availability under the 2021 RSA is calculated as follows: March 31, 2022 December 31, 2021 (In thousands) Borrowing base, based on eligible receivables $ 400,000 $ 400,000 Less: outstanding borrowings 1 (279,000) (279,000) Less: outstanding letters of credit, net (65,300) (65,300) Availability under accounts receivable securitization facilities $ 55,700 $ 55,700 1 As of March 31, 2022 and December 31, 2021, outstanding borrowings are included in "Accounts receivable securitization – less current portion" in the condensed consolidated balance sheets and are offset by $0.5 million of deferred loan costs. Interest accrued on the aggregate principal balance at a rate of 1.1% and 0.9% as of March 31, 2022 and December 31, 2021, respectively.

Debt And Financing (Tables)

Debt And Financing (Tables)	3 Months Ended
	Mar. 31, 2022
Debt Disclosure [Abstract]
Schedule of Debt Balances by Instrument	Other than the Company's accounts receivable securitization as discussed in Note 5, the Company's long-term debt consisted of the following: March 31, 2022 December 31, 2021 (In thousands) 2021 Term Loan A-1, due December 3, 2022, net 1 2 $ 169,765 $ 199,676 2021 Term Loan A-2, due September 3, 2024, net 1 2 199,645 199,607 2021 Term Loan A-3, due September 3, 2026, net 1 2 798,440 798,352 2021 Prudential Notes, net 1 39,261 47,265 Other 4,567 5,069 Total long-term debt, including current portion 1,211,678 1,249,969 Less: current portion of long-term debt (182,519) (212,417) Long-term debt, less current portion $ 1,029,159 $ 1,037,552 March 31, 2022 December 31, 2021 (In thousands) Total long-term debt, including current portion $ 1,211,678 $ 1,249,969 2021 Revolver, due September 3, 2026 1 3 165,000 260,000 Long-term debt, including revolving line of credit $ 1,376,678 $ 1,509,969 1 Refer to Note 12 for information regarding the fair value of debt. 2 The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.2 million, $0.4 million, and $1.6 million in deferred loan costs as of March 31, 2022, respectively. The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 3 The Company also had outstanding letters of credit of $64.4 million and $64.0 million under the 2021 Revolver, primarily related to workers' compensation and self-insurance liabilities at March 31, 2022 and December 31, 2021, respectively.
Schedule of Long-term Debt Instruments	The following table presents the key terms of the 2021 Debt Agreement: 2021 Term Loan A-1 2021 Term Loan A-2 2021 Term Loan A-3 2021 Revolver 2 2021 Debt Agreement Terms (Dollars in thousands) Maximum borrowing capacity $200,000 $200,000 $800,000 $1,100,000 Final maturity date December 3, 2022 September 3, 2024 September 3, 2026 September 3, 2026 Interest rate minimum margin BSBY BSBY BSBY BSBY Interest rate minimum margin 1 0.75% 0.75% 0.88% 0.88% Interest rate maximum margin 1 1.38% 1.38% 1.50% 1.50% Minimum principal payment — amount $— $— $10,000 $— Minimum principal payment — frequency Once Once Quarterly Once Minimum principal payment — commencement date December 3, 2022 September 3, 2024 September 30, 2024 September 3, 2026 1 The interest rate margin for the 2021 Term Loans and 2021 Revolver is based on the Company's consolidated leverage ratio. As of March 31, 2022, interest accrued at 1.08% on the 2021 Term Loans and 1.13% on the 2021 Revolver. 2 The commitment fee for the unused portion of the 2021 Revolver is based on the Company's consolidated leverage ratio, and ranges from 0.1% to 0.2%. As of March 31, 2022, commitment fees on the unused portion of the 2021 Revolver accrued at 0.1% and outstanding letter of credit fees accrued at 1.0%.

Defined Benefit Pension Plan (T

Defined Benefit Pension Plan (Tables)	3 Months Ended
	Mar. 31, 2022
Retirement Benefits [Abstract]
Defined Benefit Plan, Assumptions	The following weighted-average assumptions were used to determine net periodic pension cost: Quarter Ended March 31, 2022 Discount rate 2.55 % Expected long-term rate of return on pension plan assets 6.00 %

Contingencies and Legal Proce_2

Contingencies and Legal Proceedings (Tables)	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Schedule of Loss Contingencies by Contingency	EMPLOYEE COMPENSATION AND PAY PRACTICES MATTERS California Wage, Meal, and Rest Class Actions The plaintiffs generally allege one or more of the following: that the Company 1) failed to pay the California minimum wage; 2) failed to provide proper meal and rest periods; 3) failed to timely pay wages upon separation from employment; 4) failed to pay for all hours worked; 5) failed to pay overtime; 6) failed to properly reimburse work-related expenses; and 7) failed to provide accurate wage statements. Plaintiff(s) Defendant(s) Date instituted Court or agency currently pending in John Burnell 1 Swift Transportation Co., Inc March 22, 2010 United States District Court for the Central District of California James R. Rudsell 1 Swift Transportation Co. of Arizona, LLC and Swift Transportation Company April 5, 2012 United States District Court for the Central District of California Recent Developments and Current Status In April 2019, the parties reached settlement of this matter. In January 2020, the court granted final approval of the settlement. Two objectors appealed the court’s decision granting final approval of the settlement. The likelihood that a loss has been incurred is probable and estimable, and the loss has accordingly been accrued as of March 31, 2022. INDEPENDENT CONTRACTOR MATTERS Ninth Circuit Independent Contractor Misclassification Class Action The putative class alleges that Swift misclassified independent contractors as independent contractors, instead of employees, in violation of the Fair Labor Standards Act and various state laws. The lawsuit also raises certain related issues with respect to the lease agreements that certain independent contractors have entered into with Interstate Equipment Leasing, LLC. The putative class seeks unpaid wages, liquidated damages, interest, other costs, and attorneys' fees. Plaintiff(s) Defendant(s) Date instituted Court or agency currently pending in Joseph Sheer, Virginia Van Dusen, Jose Motolinia, Vickii Schwalm, Peter Wood 1 Swift Transportation Co., Inc., Interstate Equipment Leasing, Inc., Jerry Moyes, and Chad Killebrew December 22, 2009 United States District Court of Arizona and Ninth Circuit Court of Appeals Recent Developments and Current Status In January 2020, the court granted final approval of the settlement in this matter. In March 2020, the Company paid the settlement amount approved by the court. As of March 31, 2022, the Company has accrued for anticipated costs associated with finalizing this matter. 1 Individually and on behalf of all others similarly situated.

Share Repurchase Plans (Tables)

Share Repurchase Plans (Tables)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Schedule of Share Repurchases	The following table presents the Company's repurchases of its common stock under the respective share repurchase plans, excluding advisory fees: Share Repurchase Plan Quarter Ended March 31, 2022 Quarter Ended March 31, 2021 Board Approval Date Authorized Amount Shares Amount Shares Amount (shares and dollars in thousands) November 24, 2020 1 $250,000 2,723 $ 144,881 1,303 $ 53,661 1 $47.9 million and $192.8 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of March 31, 2022 and December 31, 2021, respectively.

Weighted Average Shares Outst_2

Weighted Average Shares Outstanding (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Calculation Of Basic And Diluted Earnings Per Share Attributable To Stockholders	The following table reconciles basic weighted average shares outstanding to diluted weighted average shares outstanding: Quarter Ended March 31, 2022 2021 (In thousands) Basic weighted average common shares outstanding 165,377 167,478 Dilutive effect of equity awards 1,122 896 Diluted weighted average common shares outstanding 166,499 168,374 Anti-dilutive shares excluded from diluted earnings per share 1 239 6 1 Shares were excluded from the dilutive-effect calculation because the outstanding awards' exercise prices were greater than the average market price of the Company's common stock for the periods presented.

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value by Balance Sheet Grouping	The following table presents the carrying amounts and estimated fair values of the Company's major categories of financial assets and liabilities: March 31, 2022 December 31, 2021 Condensed Consolidated Balance Sheets Caption Carrying Estimated Carrying Estimated (In thousands) Financial Assets: Equity method investments Other long-term assets 78,750 78,750 75,769 75,769 Investments in equity securities Other long-term assets 53,352 53,352 74,201 74,201 Convertible note Other current assets 10,437 10,437 10,141 10,141 Financial Liabilities: 2021 Term Loan A-1, due December 2022 1 Finance lease liabilities and long-term debt 169,765 170,000 199,676 200,000 2021 Term Loan A-2, due September 2024 1 Long-term debt – less current portion 199,645 200,000 199,607 200,000 2021 Term Loan A-3, due September 2026 1 Long-term debt – less current portion 798,440 800,000 798,352 800,000 2021 Revolver, due September 2026 Revolving line of credit 165,000 165,000 260,000 260,000 2021 Prudential Notes 2 Finance lease liabilities and long-term debt 39,261 39,341 47,265 47,354 2021 RSA, due April 2024 3 Accounts receivable securitization 278,539 279,000 278,483 279,000 Contingent consideration, acquisitions Accrued liabilities, Other long-term liabilities 13,100 13,100 13,100 13,100 1 The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.2 million, $0.4 million, and $1.6 million in deferred loan costs as of March 31, 2022, respectively. The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 2 The carrying amount of the 2021 Prudential Notes is net of $0.1 million in deferred loan costs as of March 31, 2022 and December 31, 2021 . T he carrying amount of the 2021 Prudential Notes is net of $2.2 million and $2.4 million in fair value adjustments as of March 31, 2022 and December 31, 2021 , respectively. 3 The carrying amount of the 2021 RSA is net of $0.5 million in deferred loan costs as of March 31, 2022 and December 31, 2021 .
Recurring Fair Value Measurements (Assets)	The following table depicts the level in the fair value hierarchy of the inputs used to estimate the fair value of assets measured on a recurring basis as of March 31, 2022 and December 31, 2021 : Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs Unrealized Gain (Loss) Position (In thousands) As of March 31, 2022 Convertible note 1 $ 10,437 $ — $ — $ 10,437 $ 296 Investments in equity securities 2 53,352 53,352 — — (7,817) As of December 31, 2021 Convertible note 1 10,141 — — 10,141 141 Investments in equity securities 2 74,201 74,201 — — 14,456 1 The Company recognized $0.3 million of unrealized gains on the convertible note for the quarter ended March 31, 2022, which is included within "Other (expense) income, net" within the condensed consolidated statement of comprehensive income. No gain was recognized on the convertible note for the quarter ended March 31, 2021. The fair value of the note was determined using a discounted cash flow analysis based on the probability of exit event options and exit event dates. 2 Fair value activity from the investments in equity securities is recorded in "Other (expense) income, net" within the condensed consolidated statement of comprehensive income. During the quarter ended March 31, 2022, the Company recognized $20.8 million in losses on these investments in equity securities, consisting of $20.8 million in unrealized losses and no realized loss. During the quarter ended March 31, 2021, the Company recognized $10.4 million in gains, consisting of $6.9 million in unrealized gains and $3.5 million in realized gains. Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs (In thousands) As of March 31, 2022 US equity funds $ 14,442 $ 14,442 $ — $ — International equity funds 5,902 5,902 — — Fixed income funds 42,431 42,431 — — Cash and cash equivalents 1,418 1,418 — — Total pension plan assets $ 64,193 $ 64,193 $ — $ — As of December 31, 2021 US equity funds $ 14,877 $ 14,877 $ — $ — International equity funds 6,304 6,304 — — Fixed income funds 47,873 47,873 — — Cash and cash equivalents 1,413 1,413 — — Total pension plan assets $ 70,467 $ 70,467 $ — $ —
Recurring Fair Value Measurements (Liabilities)	The following table depicts the level in the fair value hierarchy of the inputs used to estimate the fair value of liabilities measured on a recurring basis as of March 31, 2022 and December 31, 2021: Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Gain (Loss) (In thousands) As of March 31, 2022 Contingent consideration associated with acquisitions 1 $ 13,100 $ — $ — $ 13,100 $ — As of December 31, 2021 Contingent consideration associated with acquisition 1 13,100 — — 13,100 — 1 The Company did not recognize any gains (losses) during the quarters ended March 31, 2022 and 2021 related to the revaluation of these liabilities. Refer to Note 3 for information regarding the components of these liabilities.
Nonrecurring Fair Value Measurements (Assets)	The following table depicts the level in the fair value hierarchy of the inputs used to estimate fair value of assets measured on a nonrecurring basis as of March 31, 2022 and December 31, 2021: Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Loss (In thousands) As of March 31, 2022 Buildings 1 $ — $ — $ — $ — $ (810) As of December 31, 2021 Equipment 2 — — — — (299) 1 Reflects the non-cash impairment of building improvements (within the non-reportable segments).

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2022
Related Party Transactions [Abstract]
Related Party Transactions	Quarter Ended March 31, 2022 2021 Provided by Knight-Swift Received by Knight-Swift Provided by Knight-Swift Received by Knight-Swift (In thousands) Facility and Equipment Leases: Certain affiliates 1 — 78 — 57 Total $ — $ 78 $ — $ 57 Other Services: Certain affiliates 1 5 9 6 9 Total $ 5 $ 9 $ 6 $ 9 March 31, 2022 December 31, 2021 Receivable Payable Receivable Payable (In thousands) Certain affiliates 1 2 39 14 44 Total $ 2 $ 39 $ 14 $ 44 1 "Certain affiliates" includes entities that are associated with various board members and executives and require approval by the Board prior to completing transactions. Transactions with these entities generally include freight services, facility and equipment leases, equipment sales, and other services.

Information by Segment and Ge_2

Information by Segment and Geography (Tables)	3 Months Ended
	Mar. 31, 2022
Segment Reporting [Abstract]
Summary Of Financial Information By Segments	Quarter Ended March 31, 2022 2021 Revenue: (In thousands) Truckload $ 1,080,531 $ 962,947 Logistics 282,039 118,887 LTL 255,125 — Intermodal 109,222 107,066 Subtotal $ 1,726,917 $ 1,188,900 Non-reportable segments 117,639 50,669 Intersegment eliminations (17,567) (16,555) Total revenue $ 1,826,989 $ 1,223,014 Quarter Ended March 31, 2022 2021 Operating income (loss): (In thousands) Truckload $ 205,117 $ 158,483 Logistics 39,601 7,577 LTL 26,377 — Intermodal 15,170 3,457 Subtotal $ 286,265 $ 169,517 Non-reportable segments 11,821 (7,258) Operating income $ 298,086 $ 162,259 Quarter Ended March 31, 2022 2021 Depreciation and amortization of property and equipment: (In thousands) Truckload $ 110,349 $ 101,885 Logistics 596 208 LTL 15,260 — Intermodal 3,864 3,818 Subtotal $ 130,069 $ 105,911 Non-reportable segments 14,975 14,004 Depreciation and amortization of property and equipment $ 145,044 $ 119,915

Introduction and Basis of Pre_3

Introduction and Basis of Presentation (Details)	Dec. 06, 2021	Jul. 05, 2021	Jun. 01, 2021	Feb. 01, 2021	Mar. 31, 2022VehicleSegment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operational tractors in fleet					17,965
Number of company tractors					16,159
Number of independent contractor tractors					1,806
Number of trailers					71,310
Number of LTL tractors					3,091
Number of LTL trailers					8,302
Number of intermodal tractors					584
Number of intermodal containers					11,027
Number of reportable segments | Segment					4
MME
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Acquisition, Effective Date of Acquisition	Dec. 6, 2021
ACT
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Business Acquisition, Effective Date of Acquisition		Jul. 5, 2021
UTXL [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired			100.00%
Business Acquisition, Effective Date of Acquisition			Jun. 1, 2021
Eleos [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired				79.44%
Business Acquisition, Effective Date of Acquisition				Feb. 1, 2021

Recently Issued Accounting Pr_3

Recently Issued Accounting Pronouncements (Details) - Accounting Standards Update 2022-02 [Member]	3 Months Ended
	Mar. 31, 2022
Recently Issued Accounting Pronouncements [Line Items]
New Accounting Pronouncement Financial Statement Impact	The amendments in this ASU require that a creditor incorporates troubled debt restructurings into the allowance for credit losses and disclose current-period gross writeoffs by year of origination for financing receivables and net investments in leases.
New Accounting Pronouncement Adoption Method and Date	January 2023, Prospective
New Accounting Pronouncement Financial Statement Impact	Currently under evaluation, but not expected to be material

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 06, 2021	Jul. 05, 2021	Jun. 01, 2021	Feb. 01, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Business Acquisition [Line Items]
Goodwill	$ 3,518,589					$ 3,518,589		$ 3,515,135
Total revenue						1,826,989	$ 1,223,014
Net income						208,288	129,843
Amortization of Intangible Assets						16,166	$ 11,749
MME
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition		Dec. 6, 2021
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Fair value of the consideration transferred	165,700
MME | Revision of Prior Period, Adjustment [Member]
Business Acquisition [Line Items]
Net Working Capital Adjustment	1,300					1,300
Deferred tax liabilities	(2,200)					(2,200)
Goodwill	3,500					3,500
ACT
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Jul. 5, 2021
Business Acquisition, Percentage of Voting Interests Acquired			100.00%
Total revenue						217,700
Net income						16,100
Amortization of Intangible Assets						3,500
UTXL [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition				Jun. 1, 2021
Business Acquisition, Percentage of Voting Interests Acquired				100.00%
Eleos [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition					Feb. 1, 2021
Business Acquisition, Percentage of Voting Interests Acquired					79.44%
Contingent consideration (annual payment) [Member] | UTXL [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current	2,500					2,500
Business Combination, Contingent Consideration, Liability, Noncurrent	$ 2,500					$ 2,500

Acquisitions - Tables (Details)

Acquisitions - Tables (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)$ / shares
Business Combinations [Abstract]
Business Acquisition, Pro Forma Revenue	$ 1,412,232
Business Acquisition, Pro Forma Net Income (Loss)	$ 139,189
Business Acquisition, Pro Forma Earnings Per Share, Diluted | $ / shares	$ 0.83

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Income Tax Contingency [Line Items]
Effective tax rate	24.90%	25.90%
Deferred Tax Assets, Valuation Allowance	$ 0
Decrease in Unrecognized Tax Benefits is Reasonably Possible	0.3
Accrued interest and penalties	$ 0.1		$ 0.1
Year subject to examination	2017
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Year under income tax examination	2014
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Year under income tax examination	2020

Accounts Receivable Securitiz_3

Accounts Receivable Securitization (Details) - 2021 RSA - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Apr. 23, 2021
Servicing Liabilities at Fair Value [Line Items]
Effective date				Apr. 23, 2021
Final maturity date				Apr. 23, 2024
Receivables Sales Agreement, Borrowing Capacity				$ 400,000
Accordion Option Accounts Receivable Securitization	[1]			$ 100,000
Unused commitment fee rate	[2]			20 to 40 basis points
Program fees on outstanding balances	[3]			one-month LIBOR + 82.5 basis points
Accounts receivable securitization – less current portion		$ 400,000	$ 400,000
Accounts receivable securitization	[4]	(279,000)	(279,000)
Letters of Credit Outstanding, Amount		(65,300)	(65,300)
Availability under accounts receivable securitization facilities		55,700	55,700
Deferred loan costs		$ 500	$ 500
Debt Instrument, Interest Rate During Period		1.10%	0.90%
[1]	The accordion option increases the maximum borrowing capacity, subject to participation of the purchasers.
[2]	The 2021 RSA commitment fees rate are based on the percentage of the maximum borrowing capacity utilized.
[3]	As identified within the 2021 RSA, the lender can trigger an amendment by identifying and deciding upon a replacement for LIBOR.
[4]	As of March 31, 2022 and December 31, 2021, outstanding borrowings are included in "Accounts receivable securitization – less current portion" in the condensed consolidated balance sheets and are offset by $0.5 million of deferred loan costs. Interest accrued on the aggregate principal balance at a rate of 1.1% and 0.9% as of March 31, 2022 and December 31, 2021, respectively.

Debt And Financing - (Details)

Debt And Financing - (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Sep. 03, 2021	Dec. 31, 2021
Debt Instrument [Line Items]
Long-Term Debt		$ 1,211,678		$ 1,249,969
Less: current portion of long-term debt		(182,519)		(212,417)
Long-term debt – less current portion		1,029,159		1,037,552
Revolving line of credit		165,000		260,000
Long-term Debt		1,376,678		1,509,969
2021 Term Loan A-1
Debt Instrument [Line Items]
Long-Term Debt	[1],[2]	169,765		199,676
Line of Credit Facility, Maximum Borrowing Capacity			$ 200,000
Final maturity date			Dec. 3, 2022
Program fees on outstanding balances			BSBY
Minimum principal payment — amount			$ 0
Minimum principal payment — frequency			Once
Minimum principal payment — commencement date			Dec. 3, 2022
2021 Term Loan A-1 | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		0.75%
2021 Term Loan A-1 | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		1.38%
2021 Term Loan A-2
Debt Instrument [Line Items]
Long-Term Debt	[1],[2]	199,645		199,607
Line of Credit Facility, Maximum Borrowing Capacity			$ 200,000
Final maturity date			Sep. 3, 2024
Program fees on outstanding balances			BSBY
Minimum principal payment — amount			$ 0
Minimum principal payment — frequency			Once
Minimum principal payment — commencement date			Sep. 3, 2024
2021 Term Loan A-2 | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		0.75%
2021 Term Loan A-2 | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		1.38%
2021 Term Loan A-3
Debt Instrument [Line Items]
Long-Term Debt	[1],[2]	798,440		798,352
Line of Credit Facility, Maximum Borrowing Capacity			$ 800,000
Final maturity date			Sep. 3, 2026
Program fees on outstanding balances			BSBY
Minimum principal payment — amount			$ 10,000
Minimum principal payment — frequency			Quarterly
Minimum principal payment — commencement date			Sep. 30, 2024
2021 Term Loan A-3 | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		0.88%
2021 Term Loan A-3 | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		1.50%
2021 Prudential Notes
Debt Instrument [Line Items]
Long-Term Debt	[2]	39,261		47,265
Debt Instrument, Unused Borrowing Capacity, Amount		87,900
2021 Prudential Notes | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.05%
2021 Prudential Notes | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.40%
Other Debt
Debt Instrument [Line Items]
Secured Debt, Other		4,567		5,069
2021 Revolver
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		$ 64,400		64,000
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,100,000
Final maturity date			Sep. 3, 2026
Program fees on outstanding balances			BSBY
Minimum principal payment — amount			$ 0
Minimum principal payment — frequency			Once
Minimum principal payment — commencement date			Sep. 3, 2026
Debt Instrument, Interest Rate During Period		1.13%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.10%
Line of Credit Facility, Commitment Fee Percentage		1.00%
2021 Revolver | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3],[4]		0.88%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.10%
2021 Revolver | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3],[4]		1.50%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.20%
2021 Term Loans
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period		1.08%
Line of Credit | 2021 Revolver
Debt Instrument [Line Items]
Revolving line of credit	[2],[5]	$ 165,000		260,000
Loans Payable [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 2,300,000
Loans Payable [Member] | 2021 Term Loan A-1
Debt Instrument [Line Items]
Deferred loan costs		200		300
Loans Payable [Member] | 2021 Term Loan A-2
Debt Instrument [Line Items]
Deferred loan costs		400		400
Loans Payable [Member] | 2021 Term Loan A-3
Debt Instrument [Line Items]
Deferred loan costs		$ 1,600		$ 1,600
Loans Payable [Member] | 2021 Prudential Notes
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 125,000
[1]	The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.2 million, $0.4 million, and $1.6 million in deferred loan costs as of March 31, 2022, respectively. The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively.
[2]	Refer to Note 12 for information regarding the fair value of debt.
[3]	The interest rate margin for the 2021 Term Loans and 2021 Revolver is based on the Company's consolidated leverage ratio. As of March 31, 2022, interest accrued at 1.08% on the 2021 Term Loans and 1.13% on the 2021 Revolver.
[4]	The commitment fee for the unused portion of the 2021 Revolver is based on the Company's consolidated leverage ratio, and ranges from 0.1% to 0.2%. As of March 31, 2022, commitment fees on the unused portion of the 2021 Revolver accrued at 0.1% and outstanding letter of credit fees accrued at 1.0%.
[5]	The Company also had outstanding letters of credit of $64.4 million and $64.0 million under the 2021 Revolver, primarily related to workers' compensation and self-insurance liabilities at March 31, 2022 and December 31, 2021, respectively.

Defined Benefit Pension Plan (D

Defined Benefit Pension Plan (Details)	3 Months Ended
	Mar. 31, 2022
Retirement Benefits [Abstract]
Discount Rate (Point in Time)	3.38%
Discount Rate (Period of Time)	2.55%
Expected long-term rate of return on pension plan assets	6.00%

Commitments (Details)

Commitments (Details) $ in Millions	Mar. 31, 2022USD ($)
Capital Addition Purchase Commitments Total Revenue Equipment [Member]
Long-term Purchase Commitment [Line Items]
Purchase Obligation, to be Paid, Year One	$ 682.2
Purchase Obligation, to be Paid, Year Two	58.6
Purchase Obligation, to be Paid, Year Three	0
Purchase Obligation, Due in Fourth and Fifth Year	0
Purchase Obligation, Due after Fifth Year	0
Capital Addition Purchase Commitments of Tractors [Member]
Long-term Purchase Commitment [Line Items]
Purchase Obligation, to be Paid, Year One	479.3
Purchase Obligation, to be Paid, Year Two	50.4
Capital Addition Purchase Commitments Non revenue equipment [Member]
Long-term Purchase Commitment [Line Items]
Purchase Obligation, Future Minimum Payments, Remainder of Fiscal Year	52
Purchase Obligation, Due in Second and Third Year	6.4
Purchase Obligation, Due in Fourth and Fifth Year	1.2
Purchase Obligation, Due after Fifth Year	$ 0

Legal Proceedings (Details)

Legal Proceedings (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Commitments and Contingencies Disclosure [Abstract]
Loss contingency accrual	$ 18.6
Employee Compensation and Pay Practices Matters [Member] | California Wage, Meal, and Rest Class Action [Member]
Loss Contingencies [Line Items]
Loss contingency, allegations	The plaintiffs generally allege one or more of the following: that the Company 1) failed to pay the California minimum wage; 2) failed to provide proper meal and rest periods; 3) failed to timely pay wages upon separation from employment; 4) failed to pay for all hours worked; 5) failed to pay overtime; 6) failed to properly reimburse work-related expenses; and 7) failed to provide accurate wage statements.
Loss contingency, opinion of counsel	In April 2019, the parties reached settlement of this matter. In January 2020, the court granted final approval of the settlement. Two objectors appealed the court’s decision granting final approval of the settlement. The likelihood that a loss has been incurred is probable and estimable, and the loss has accordingly been accrued as of March 31, 2022.
Employee Compensation and Pay Practices Matters [Member] | California Wage, Meal, and Rest Class Action [Member] | California Wage, Meal, and Rest Class Action 1 [Member]
Loss Contingencies [Line Items]
Loss contingency, name of plaintiffs	John Burnell 1	[1]
Loss contingency, name of defendant	Swift Transportation Co., Inc
Lawsuit filing date	March 22, 2010
Loss contingency, domicile of litigation	United States District Court for the Central District of California
Employee Compensation and Pay Practices Matters [Member] | California Wage, Meal, and Rest Class Action [Member] | California Wage, Meal, and Rest Class Action 2 [Member]
Loss Contingencies [Line Items]
Loss contingency, name of plaintiffs	James R. Rudsell 1	[1]
Loss contingency, name of defendant	Swift Transportation Co. of Arizona, LLC and Swift Transportation Company
Lawsuit filing date	April 5, 2012
Loss contingency, domicile of litigation	United States District Court for the Central District of California
Independent Contractor Matters [Member] | Ninth circuit owner operator misclassification class action 1 [Member]
Loss Contingencies [Line Items]
Loss contingency, allegations	The putative class alleges that Swift misclassified independent contractors as independent contractors, instead of employees, in violation of the Fair Labor Standards Act and various state laws. The lawsuit also raises certain related issues with respect to the lease agreements that certain independent contractors have entered into with Interstate Equipment Leasing, LLC. The putative class seeks unpaid wages, liquidated damages, interest, other costs, and attorneys' fees.
Loss contingency, name of plaintiffs	Joseph Sheer, Virginia Van Dusen, Jose Motolinia, Vickii Schwalm, Peter Wood 1	[1]
Loss contingency, name of defendant	Swift Transportation Co., Inc., Interstate Equipment Leasing, Inc., Jerry Moyes, and Chad Killebrew
Lawsuit filing date	December 22, 2009
Loss contingency, domicile of litigation	United States District Court of Arizona and Ninth Circuit Court of Appeals
Loss contingency, opinion of counsel	In January 2020, the court granted final approval of the settlement in this matter. In March 2020, the Company paid the settlement amount approved by the court. As of March 31, 2022, the Company has accrued for anticipated costs associated with finalizing this matter.
[1]	Individually and on behalf of all others similarly situated.

Self Insurance (Details)

Self Insurance (Details) - ACT - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 31, 2022
Loss Contingencies [Line Items]
Self Insurance Retention	$ 2	$ 10
Insurance Aggregate Deductible Amount	5
Maximum [Member]
Loss Contingencies [Line Items]
Insurance Aggregate Deductible Amount	$ 10

Share Repurchase Plans (Details

Share Repurchase Plans (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Nov. 24, 2020
Class of Stock [Line Items]
Company shares repurchased		$ 144,881	$ 53,661
Knight-Swift Share Repurchase Plan, November 24, 2020
Class of Stock [Line Items]
Share repurchase plan, authorized amount, value	[1]				$ 250,000
Share repurchase, shares	[1]	2,723	1,303
Company shares repurchased	[1]	$ 144,881	$ 53,661
Share repurchase plan, remaining authorized amount, value		$ 47,900		$ 192,800
[1]	$47.9 million and $192.8 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of March 31, 2022 and December 31, 2021, respectively.

Share Repurchase Plans - Subseq

Share Repurchase Plans - Subsequent Events - (Details) - USD ($) shares in Thousands, $ in Thousands		May 04, 2022	Mar. 31, 2022	Mar. 31, 2021	Apr. 25, 2022	Dec. 31, 2021	Nov. 24, 2020
Class of Stock [Line Items]
Company shares repurchased			$ 144,881	$ 53,661
Knight-Swift Share Repurchase Plan, November 24, 2020
Class of Stock [Line Items]
Share repurchase plan, authorized amount, value	[1]						$ 250,000
Share repurchase, shares	[1]		2,723	1,303
Company shares repurchased	[1]		$ 144,881	$ 53,661
Share repurchase plan, remaining authorized amount, value			$ 47,900			$ 192,800
Subsequent Event [Member] | Knight-Swift Share Repurchase Plan, November 24, 2020
Class of Stock [Line Items]
Share repurchase, shares		100
Company shares repurchased		$ 5,100
Share repurchase plan, remaining authorized amount, value					$ 42,800
Subsequent Event [Member] | Knight-Swift Share Repurchase Plan, April 25, 2022
Class of Stock [Line Items]
Share repurchase plan, authorized amount, value					$ 350,000
Share repurchase, shares		400
Company shares repurchased		$ 17,300
Share repurchase plan, remaining authorized amount, value		$ 332,700
[1]	$47.9 million and $192.8 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of March 31, 2022 and December 31, 2021, respectively.

Weighted Average Shares Outst_3

Weighted Average Shares Outstanding (Details) - shares shares in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Basic weighted average common shares outstanding		165,377	167,478
Dilutive effect of equity awards		1,122	896
Diluted weighted average common shares outstanding		166,499	168,374
Anti-dilutive shares excluded from diluted earnings per share	[1]	239	6
[1]	Shares were excluded from the dilutive-effect calculation because the outstanding awards' exercise prices were greater than the average market price of the Company's common stock for the periods presented.

Fair Value Measurement - Estima

Fair Value Measurement - Estimated Fair Values (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021
Financial Assets:
Equity method investments		$ 78,750	$ 75,769
Equity method investments (Estimated Fair Value)		78,750	75,769
Investments in equity securities		53,352	74,201
Convertible note		10,437	10,141
Financial Liabilities:
Term loan Carrying Value		1,376,678	1,509,969
Revolving line of credit		165,000	260,000
Accounts receivable securitization		278,539	278,483
Business Combination, Contingent Consideration, Liability		13,100	13,100
2021 Term Loan A-1
Financial Liabilities:
Term loan Carrying Value	[1]	169,765	199,676
Term loan, Fair Value	[1]	170,000	200,000
2021 Term Loan A-2
Financial Liabilities:
Term loan Carrying Value	[1]	199,645	199,607
Term loan, Fair Value	[1]	200,000	200,000
2021 Term Loan A-3
Financial Liabilities:
Term loan Carrying Value	[1]	798,440	798,352
Term loan, Fair Value	[1]	800,000	800,000
2021 Revolver
Financial Liabilities:
Revolving line of credit		165,000	260,000
2021 Prudential Notes
Financial Liabilities:
Term loan Carrying Value	[2]	39,261	47,265
Term loan, Fair Value	[2]	39,341	47,354
Debt Instrument, Fair Value Disclosure		2,200	2,400
Deferred loan costs			100
2021 RSA
Financial Liabilities:
Accounts receivable securitization	[3]	278,539	278,483
Debt Instrument, Fair Value Disclosure	[3]	279,000	279,000
Deferred loan costs		$ 500	$ 500
[1]	The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are net of $0.2 million, $0.4 million, and $1.6 million in deferred loan costs as of March 31, 2022, respectively. The carrying amounts of the 2021 Term Loan A-1, 2021 Term Loan A-2, and 2021 Term Loan A-3 are
[2]	The carrying amount of the 2021 Prudential Notes is net of $0.1 million in deferred loan costs as of March 31, 2022 and December 31, 2021 . T he carrying amount of the 2021 Prudential Notes is net of $2.2 million and $2.4 million in fair value adjustments as of March 31, 2022 and December 31, 2021 , respectively.
[3]	The carrying amount of the 2021 RSA is net of $0.5 million in deferred loan costs as of March 31, 2022 and December 31, 2021 .

Fair Value Measurement - Recurr

Fair Value Measurement - Recurring and Nonrecurring Measurements (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2022		Mar. 31, 2021	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible note		$ 10,437			$ 10,141
Business Combination, Contingent Consideration, Liability		13,100			13,100
Gain (Loss) on Disposition of Property Plant Equipment		34,801		$ 10,537
Equipment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (Loss) on Disposition of Property Plant Equipment		34,800		10,500
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible note	[1]	10,437			10,141
Gain (Loss) on Investments		296	[1]	0	141	[1]
Assets, Fair Value Disclosure	[2]	53,352			74,201
Fair Value, Option, Changes in Fair Value, Gain (Loss)	[2]	(7,817)			14,456
Debt and Equity Securities, Gain (Loss)		(20,800)		10,400
Debt and Equity Securities, Unrealized Gain (Loss)		(20,800)		6,900
Debt and Equity Securities, Realized Gain (Loss)		0		3,500
Business Combination, Contingent Consideration, Liability	[3]	13,100			13,100
Contingent Consideration Gain (Loss)		0	[3]	$ 0	0	[3]
Total pension plan assets		64,193			70,467
Fair Value, Recurring [Member] | Embark
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		37,000
Debt and Equity Securities, Unrealized Gain (Loss)		17,500
Fair Value, Recurring [Member] | US equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		14,442			14,877
Fair Value, Recurring [Member] | International equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		5,902			6,304
Fair Value, Recurring [Member] | Fixed income funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		42,431			47,873
Fair Value, Recurring [Member] | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		1,418			1,413
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible note	[1]	0			0
Assets, Fair Value Disclosure	[2]	53,352			74,201
Business Combination, Contingent Consideration, Liability	[3]	0			0
Total pension plan assets		64,193			70,467
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		14,442			14,877
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | International equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		5,902			6,304
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed income funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		42,431			47,873
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		1,418			1,413
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible note	[1]	0			0
Assets, Fair Value Disclosure	[2]	0			0
Business Combination, Contingent Consideration, Liability	[3]	0			0
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | International equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed income funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible note	[1]	10,437			10,141
Assets, Fair Value Disclosure	[2]	0			0
Business Combination, Contingent Consideration, Liability	[3]	13,100			13,100
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | International equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed income funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total pension plan assets		0			0
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0			0
Building and Building Improvements | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	[4]	0
Total Losses, nonrecurring assets	[4]	$ (810)
Equipment [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	[5]				0
Total Losses, nonrecurring assets	[5]				(299)
Equipment [Member] | Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	[5]				0
Equipment [Member] | Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	[5]				0
Equipment [Member] | Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	[5]				$ 0
[1]	The Company recognized $0.3 million of unrealized gains on the convertible note for the quarter ended March 31, 2022, which is included within "Other (expense) income, net" within the condensed consolidated statement of comprehensive income. No gain was recognized on the convertible note for the quarter ended March 31, 2021. The fair value of the note was determined using a discounted cash flow analysis based on the probability of exit event options and exit event dates.
[2]	Fair value activity from the investments in equity securities is recorded in "Other (expense) income, net" within the condensed consolidated statement of comprehensive income. During the quarter ended March 31, 2022, the Company recognized $20.8 million in losses on these investments in equity securities, consisting of $20.8 million in unrealized losses and no realized loss. During the quarter ended March 31, 2021, the Company recognized $10.4 million in gains, consisting of $6.9 million in unrealized gains and $3.5 million in realized gains.
[3]	The Company did not recognize any gains (losses) during the quarters ended March 31, 2022 and 2021 related to the revaluation of these liabilities. Refer to Note 3 for information regarding the components of these liabilities.
[4]	Reflects the non-cash impairment of building improvements (within the non-reportable segments).
[5]	Reflects the non-cash impairment of certain revenue equipment held for sale (within the non-reportable segments and the Truckload segment).

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Related Party Transaction [Line Items]
Receivable		$ 2		$ 14
Payable		39		44
Facility and Equipment Leases [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift		0	$ 0
Received by Knight-Swift		78	57
Other Services [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift		5	6
Received by Knight-Swift		9	9
Certain Affiliates [Member]
Related Party Transaction [Line Items]
Receivable	[1]	2		14
Payable	[1]	39		$ 44
Certain Affiliates [Member] | Facility and Equipment Leases [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	0
Received by Knight-Swift	[1]	78	57
Certain Affiliates [Member] | Other Services [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	5	6
Received by Knight-Swift	[1]	$ 9	$ 9
[1]	"Certain affiliates" includes entities that are associated with various board members and executives and require approval by the Board prior to completing transactions. Transactions with these entities generally include freight services, facility and equipment leases, equipment sales, and other services.

Information by Segment and Ge_3

Information by Segment and Geography - Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Total revenue	$ 1,826,989	$ 1,223,014
Operating income (loss)	298,086	162,259
Depreciation and amortization of property and equipment	145,044	119,915
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenue	1,726,917	1,188,900
Operating income (loss)	286,265	169,517
Depreciation and amortization of property and equipment	130,069	105,911
Operating Segments [Member] | Truckload [Member]
Segment Reporting Information [Line Items]
Total revenue	1,080,531	962,947
Operating income (loss)	205,117	158,483
Depreciation and amortization of property and equipment	110,349	101,885
Operating Segments [Member] | Logistics [Member]
Segment Reporting Information [Line Items]
Total revenue	282,039	118,887
Operating income (loss)	39,601	7,577
Depreciation and amortization of property and equipment	596	208
Operating Segments [Member] | LTL
Segment Reporting Information [Line Items]
Total revenue	255,125	0
Operating income (loss)	26,377	0
Depreciation and amortization of property and equipment	15,260	0
Operating Segments [Member] | Intermodal [Member]
Segment Reporting Information [Line Items]
Total revenue	109,222	107,066
Operating income (loss)	15,170	3,457
Depreciation and amortization of property and equipment	3,864	3,818
Non-reportable segments [Member]
Segment Reporting Information [Line Items]
Total revenue	117,639	50,669
Operating income (loss)	11,821	(7,258)
Depreciation and amortization of property and equipment	14,975	14,004
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenue	$ (17,567)	$ (16,555)

Information by Segment and Ge_4

Information by Segment and Geography - Narrative (Details)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting [Abstract]
Percentages Of Foreign Operations Consolidated Revenue	5.00%	5.00%
Long lived assets of foreign operations	5.00%		5.00%