Knight-Swift Transportation (KNX) 10-K 24 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 15, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 7,426,391,060
Entity Common Stock, Shares Outstanding		166,191,076
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive proxy statement for its 2022 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission (the "SEC") are incorporated by reference into Part III of this report.
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001492691
Current Fiscal Year End Date	--12-31
Auditor Firm ID	248
Auditor Name	GRANT THORNTON LLP
Auditor Location	Phoenix, Arizona

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) shares in Thousands, $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents		$ 261,001	$ 156,699
Cash and cash equivalents – restricted	[1]	87,241	39,328
Restricted investments, held-to-maturity, amortized cost	[2]	5,866	9,001
Trade receivables, net of allowance for doubtful accounts of $21,663 and $22,093, respectively		911,336	578,479
Allowance for doubtful accounts		21,663	22,093
Contract balance – revenue in transit		22,936	14,560
Prepaid expenses		90,507	71,649
Assets held for sale		8,166	29,756
Income tax receivable		909	2,903
Other current assets		26,318	20,988
Total current assets		1,414,280	923,363
Property and equipment:
Revenue equipment		3,994,519	3,417,194
Land and land improvements		326,731	236,517
Buildings and building improvements		639,990	458,464
Furniture and fixtures		97,102	69,250
Shop and service equipment		46,640	29,033
Leasehold improvements		13,915	12,890
Total property and equipment		5,118,897	4,223,348
Less: accumulated depreciation and amortization		(1,563,533)	(1,230,696)
Property and equipment, net		3,555,364	2,992,652
Operating lease right-of-use-assets		147,540	113,296
Goodwill	[3]	3,515,135	2,922,964
Intangible assets, net		1,831,049	1,389,245
Other long-term assets		192,132	126,482
Total assets		10,655,500	8,468,002
Current liabilities:
Accounts payable		224,844	101,001
Accrued payroll and purchased transportation		217,084	160,888
Accrued liabilities		128,536	88,894
Claims accruals – current portion		206,607	174,928
Finance lease liabilities and long-term debt – current portion		262,423	52,583
Operating lease liabilities – current portion		35,322	47,496
Accounts receivable securitization – current portion		0	213,918
Total current liabilities		1,074,816	839,708
Revolving line of credit		260,000	210,000
Long-term debt – less current portion		1,037,552	298,907
Finance lease liabilities – less current portion		256,166	138,243
Operating lease liabilities – less current portion		107,614	69,852
Accounts receivable securitization – less current portion		278,483	0
Claims accruals – less current portion		210,714	174,814
Deferred tax liabilities		874,877	815,941
Other long-term liabilities		11,828	48,497
Total liabilities		4,112,050	2,595,962
Commitments and Contingencies
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 10,000 shares authorized; none issued		$ 0	$ 0
Preferred stock, par value		$ 0.01	$ 0.01
Preferred stock, shares authorized		10,000	10,000
Common stock, par value $0.01 per share; 500,000 shares authorized; 165,980 and 166,553 shares issued and outstanding as of December 31, 2021 and 2020, respectively.		$ 1,660	$ 1,665
Accumulated Other Comprehensive Income (Loss), Net of Tax		(563)	0
Additional paid-in capital		4,350,913	4,301,424
Retained earnings		2,181,142	1,566,759
Total Knight-Swift stockholders' equity		6,533,152	5,869,848
Noncontrolling interest		10,298	2,192
Total stockholders’ equity		6,543,450	5,872,040
Total liabilities and stockholders’ equity		$ 10,655,500	$ 8,468,002
Common Stock [Member]
Stockholders’ equity:
Common stock, par value		$ 0.01	$ 0.01
Common stock, shares authorized		500,000	500,000
Beginning balance, shares		165,980	166,553
[1]	Reflects cash and cash equivalents that are primarily restricted for claims payments
[2]	Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity.
[3]	Except for the net accumulated amortization related to deferred tax assets in the Truckload segment, the net carrying amount and gross carrying amount are equal since there are no accumulated impairment losses.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 5,998,019	$ 4,673,863	$ 4,843,950
Operating expenses:
Salaries, wages, and benefits	1,771,772	1,483,188	1,474,073
Fuel	546,256	416,307	583,123
Operations and maintenance	313,505	275,290	322,188
Insurance and claims	275,378	192,840	194,336
Operating taxes and licenses	98,784	87,422	88,481
Communications	22,486	19,596	19,520
Depreciation and amortization of property and equipment	522,596	460,775	420,082
Amortization of intangibles	55,299	45,895	42,876
Rental expense	55,161	86,640	122,738
Purchased transportation	1,320,888	936,649	1,035,969
Impairments	299	5,335	3,486
Miscellaneous operating expenses	49,898	99,488	109,640
Total operating expenses	5,032,322	4,109,425	4,416,512
Operating income	965,697	564,438	427,438
Other (expenses) income:
Interest income	1,173	1,928	3,834
Interest expense	(21,140)	(17,309)	(29,433)
Other income, net	28,905	11,254	12,137
Total other (expenses) income, net	8,938	(4,127)	(13,462)
Income before income taxes	974,635	560,311	413,976
Income tax expense	230,887	149,676	103,798
Net income	743,748	410,635	310,178
Net income attributable to noncontrolling interest	(360)	(633)	(972)
Net income attributable to Knight-Swift	743,388	410,002	309,206
Other comprehensive loss	(563)	0	0
Comprehensive income	$ 742,825	$ 410,002	$ 309,206
Earnings Per Share [Abstract]
Basic earnings per share	$ 4.48	$ 2.42	$ 1.80
Diluted earnings per share	4.45	2.40	1.80
Dividends declared per share: (in dollars per share)	$ 0.38	$ 0.32	$ 0.24
Shares used in per share calculations
Basic (in shares)	165,860	169,711	171,541
Diluted (in shares)	167,060	170,549	172,142
Revenue, excluding trucking fuel surcharge [Member]
Total revenue	$ 5,531,890	$ 4,369,207	$ 4,395,332
Truckload and LTL fuel surcharge
Total revenue	$ 466,129	$ 304,656	$ 448,618

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent	Parent [Member]	Noncontrolling Interest [Member]	Common Stock [Member]	Common Stock [Member]Common Stock [Member]
Beginning balance (Shares) at Dec. 31, 2018								172,844
Beginning balance, value at Dec. 31, 2018	$ 5,462,719		$ 4,242,369	$ 1,216,852	$ 0	$ 5,460,949	$ 1,770		$ 1,728
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued to employees (Shares)								621
Common stock issued to employees	10,478		10,471			10,478			7
Common stock issued to the Board (Shares)								19
Common stock issued to the Board	531		531			531			0
Value of common stock issued for acquisition	0
Common stock issued under ESPP (Shares)								78
Common stock issued under ESPP	2,298		2,297			2,298			1
Company shares repurchased (Shares)								(2,874)
Company shares repurchased	(86,892)			(86,863)		(86,892)			(29)
Shares withheld – RSU settlement	(2,330)			(2,330)		(2,330)
Employee stock-based compensation expense	$ 13,375		13,375			13,375
Dividends declared per share: (in dollars per share)	$ 0.24
Cash dividends paid and dividends accrued	$ (41,400)			(41,400)		(41,400)
Net income attributable to Knight-Swift	309,206			309,206		309,206
Distribution to noncontrolling interest	(654)						(654)
Net income attributable to noncontrolling interest	972						972
Ending balance (Shares) at Dec. 31, 2019								170,688
Ending balance, value at Dec. 31, 2019	5,668,303		4,269,043	1,395,465	0	5,666,215	2,088		1,707
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued to employees (Shares)								631
Common stock issued to employees	10,013		10,007			10,013			6
Common stock issued to the Board (Shares)								13
Common stock issued to the Board	515		515			515			0
Value of common stock issued for acquisition	0
Common stock issued under ESPP (Shares)								62
Common stock issued under ESPP	2,220		2,220			2,220			0
Company shares repurchased (Shares)		(4,841)						(4,841)
Company shares repurchased	(179,585)			(179,537)		(179,585)			(48)
Shares withheld – RSU settlement	(4,510)			(4,510)		(4,510)
Employee stock-based compensation expense	$ 19,639		19,639			19,639
Dividends declared per share: (in dollars per share)	$ 0.32
Cash dividends paid and dividends accrued	$ (54,661)			(54,661)		(54,661)
Net income attributable to Knight-Swift	410,002			410,002		410,002
Distribution to noncontrolling interest	(529)						(529)
Net income attributable to noncontrolling interest	633						633
Ending balance (Shares) at Dec. 31, 2020								166,553
Ending 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)								510
Common stock issued to employees	5,924		5,918			5,924			6
Common stock issued to the Board (Shares)								12
Common stock issued to the Board	575		575			575			0
Common stock issued for acquisition (Shares)								219
Value of common stock issued for acquisition	10,000		9,998			10,000			2
Common stock issued under ESPP (Shares)								63
Common stock issued under ESPP	2,783		2,782			2,783			1
Company shares repurchased (Shares)		(1,377)						(1,377)
Company shares repurchased	(57,175)			(57,161)		(57,175)			(14)
Shares withheld – RSU settlement	(8,257)			(8,257)		(8,257)
Employee stock-based compensation expense	$ 33,495		33,495			33,495
Dividends declared per share: (in dollars per share)	$ 0.38
Cash dividends paid and dividends accrued	$ (63,587)			(63,587)		(63,587)
Net income attributable to Knight-Swift	743,388			743,388		743,388
Other comprehensive income	(563)				(563)	(563)
Noncontrolling interest associated with acquisition	10,281						10,281
Distribution to noncontrolling interest	(64)						(64)
Net income attributable to noncontrolling interest	360						360
Net acquisition of remaining ownership interest, previously noncontrolling	(5,750)		(3,279)			(3,279)	(2,471)
Ending balance (Shares) at Dec. 31, 2021								165,980
Ending balance, value at Dec. 31, 2021	$ 6,543,450		$ 4,350,913	$ 2,181,142	$ (563)	$ 6,533,152	$ 10,298		$ 1,660

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Net Income	$ 743,748	$ 410,635	$ 310,178
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment, and intangibles	577,895	506,670	462,958
Gain on sale of property and equipment	(74,799)	(9,706)	(32,935)
Impairments	299	5,335	3,486
Deferred income taxes	39,929	46,214	30,731
Non-cash lease expense	45,192	80,891	120,769
Other adjustments to reconcile net income to net cash provided by operating activities	28,279	43,682	24,156
Increase (decrease) in cash resulting from changes in:
Trade receivables	(214,573)	(75,521)	70,106
Income tax receivable	2,528	14,123	(10,069)
Accounts payable	73,371	7,500	(13,180)
Accrued liabilities and claims accrual	40,872	(31,210)	(919)
Operating lease liabilities	(48,171)	(83,675)	(121,737)
Other assets and liabilities	(24,417)	4,707	(3,950)
Net cash provided by operating activities	1,190,153	919,645	839,594
Cash flows from investing activities:
Proceeds from maturities of held-to-maturity investments	10,624	13,675	22,695
Purchases of held-to-maturity investments	(7,706)	(16,936)	(14,302)
Proceeds from sale of property and equipment, including assets held for sale	252,080	133,230	260,140
Purchases of property and equipment	(534,096)	(521,067)	(829,977)
Expenditures on assets held for sale	(1,367)	(483)	(16,093)
Net cash, restricted cash, and equivalents invested in acquisitions	(1,496,208)	(46,811)	(1,885)
Payments to Acquire Debt Securities, Available-for-sale	(35,000)	0	0
Other cash flows from investing activities	(5,060)	(42,320)	(4,284)
Net cash used in investing activities	(1,816,733)	(480,712)	(583,706)
Cash flows from financing activities:
Repayment of finance leases and long-term debt	(409,889)	(148,910)	(115,642)
Proceeds from long-term debt	1,200,000	0	0
Borrowings (repayments) on revolving lines of credit, net	50,000	(69,000)	84,000
Borrowings under accounts receivable securitization	80,000	61,000	150,000
Repayment of accounts receivable securitization	(15,000)	(52,000)	(185,000)
Proceeds from common stock issued	9,282	12,748	13,307
Repurchases of the Company's common stock	(57,175)	(179,585)	(86,892)
Dividends paid	(63,535)	(54,620)	(41,425)
Other cash flows from financing activities	(14,357)	(13,517)	(2,984)
Net cash provided by (used in) financing activities	779,326	(443,884)	(184,636)
Net increase (decrease) in cash, restricted cash, and equivalents	152,746	(4,951)	71,252
Cash, restricted cash, and equivalents at beginning of period	197,277	202,228	130,976
Cash, restricted cash, and equivalents at end of period	350,023	197,277	202,228
Cash paid during the period for:
Interest	18,949	17,396	28,916
Income taxes	167,092	80,006	78,658
Other Significant Noncash Transactions [Line Items]
Equipment acquired included in accounts payable	10,489	651	6,748
Equipment sales receivables	67	223	1,333
Contingent consideration associated with acquisition	6,250	16,200	0
Value of common stock issued for acquisition	10,000	0	0
Debt Conversion, Converted Instrument, Amount	37,631	0	0
Right-of-use assets obtained in exchange for operating lease liabilities	22,771	12,406	9,803
Property and equipment obtained in exchange for new finance lease liabilities	181,234	137,097	0
Financing provided to independent contractors for equipment sold [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities	4,773	5,428	5,288
Transfers from property and equipment to assets held for sale [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities	92,445	75,292	137,391
Noncontrolling Interest Associated With Acquisition
Other Significant Noncash Transactions [Line Items]
Other non-cash investing and financing activities	10,281	0	0
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 new finance lease liabilities	42,298	67,430	56,352
2021 Acquisitions
Other Significant Noncash Transactions [Line Items]
Right-of-use assets obtained in exchange for operating lease liabilities	50,988
Warehousing Co
Other Significant Noncash Transactions [Line Items]
Contingent consideration associated with acquisition	$ 6,700
Right-of-use assets obtained in exchange for operating lease liabilities		$ 12,356	$ 0

Consolidated Statements Of Ca_2

Consolidated Statements Of Cash Flows Reconciliation of Cash, Restricted Cash, and Cash Equivalents - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents		$ 261,001	$ 156,699	$ 159,722
Cash and cash equivalents – restricted	[1]	87,241	39,328	41,331
Restricted Cash and Cash Equivalents, Noncurrent	[1]	1,781	1,250	1,175
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 350,023	$ 197,277	$ 202,228
[1]	Reflects cash and cash equivalents that are primarily restricted for claims payments

Introduction and Basis of Prese

Introduction and Basis of Presentation	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Introduction and Basis of Presentation [Text Block]	Introduction and Basis of Presentation Certain acronyms and terms used throughout this Annual Report are specific to Knight-Swift, 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 2021, the Truckload segment operated an average of 18,019 tractors (comprised of 16,166 company tractors and 1,853 independent contractor tractors). The Company operated 67,606 trailers during the year, including trailers within the Truckload segment and leasing activities within the non-reportable segments. The LTL segment operated an average 2,735 tractors and 7,413 trailers. Additionally, the Intermodal segment operated an average of 597 tractors and 10,847 intermo dal cont ainers. The Company's four reportable segments are Truckload, Logistics, LTL, and Intermodal. 2017 Merger On September 8, 2017, the Company became Knight-Swift Transportation Holdings Inc. upon the effectiveness of the 2017 Merger. Immediately upon the consummation of the 2017 Merger, former Knight stockholders and former Swift stockholders owned approximately 46.0% and 54.0%, respectively, of the Company. Upon closing of the 2017 Merger, the shares of Knight common stock that previously traded under the ticker symbol "KNX" ceased trading and were delisted from the NYSE. The shares of Class A common stock commenced trading on the NYSE on a post-reverse split basis under the ticker symbol "KNX" on September 11, 2017. Recent 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 consolidated financial statements. • 100.0% of Warehousing Co. on January 1, 2020. The results are included within the non-reportable segments. 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 4 . Basis of Presentation The consolidated financial statements include the accounts of Knight-Swift Transportation Holdings Inc. and its subsidiaries. In management's opinion, these consolidated financial statements were prepared in accordance with GAAP and include all adjustments necessary (consisting of normal recurring adjustments) for the fair presentation of the periods presented. With respect to transactional/durational data, references to "years", including "2021", "2020", and "2019" pertain to calendar years. Similarly, references to "quarters", including "first", "second", "third", and "fourth" pertain to calendar quarters. Seasonality In the full 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. At the same time, operating expenses generally increase, and tractor productivity of the Company's Truckload fleet, independent contractors, and third-party carriers 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 third quarter and continuing into the fourth quarter, the Company typically experiences surges pertaining to holiday shopping trends toward delivery of gifts purchased over the Internet as well as the length of the holiday season (consumer shopping days between Thanksgiving and Christmas). However, as the Company continues to diversify its business through expansion into the LTL industry, warehousing, and other activities, seasonal volatility is becoming more tempered. Additionally, macroeconomic trends and cyclical changes in the trucking industry, including imbalances in supply and demand, can override the seasonality faced in the industry. Impact of COVID-19 The Company continues to operate its business through the COVID-19 pandemic, including its variants, and has taken additional precautions to ensure the safety of its employees, customers, vendors, and the communities in which it operates. Various uncertainties have arisen from the COVID-19 pandemic. While management is continuing to monitor the impact of the pandemic on Knight-Swift, including its employees, customers, vendors, independent contractors, stockholders, and other business partners and stakeholders, it is difficult to predict the impact that the pandemic will have on future results of its operations, financial position, and liquidity. This has caused some uncertainties around various accounting estimates. Due to these uncertainties, the Company's accounting estimates may change, as management's assessment of the impacts of the COVID-19 pandemic continues to evolve. ASUs There were various ASUs that became effective during 2021, which did not have a material impact on the Company's results of operations, financial position, cash flows, or disclosures.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies [Text Block]	Summary of Significant Accounting Policies Use of Estimates — The preparation of the consolidated financial statements, in accordance with GAAP, requires management to make estimates and assumptions about future events that affect the amounts reported in the Company's consolidated financial statements and accompanying notes. On an ongoing basis, management evaluates and periodically adjusts its estimates and assumptions, based on historical experience, the impact of the current economic environment, and other key factors. Volatile energy markets, as well as changes in consumer spending have increased the inherent uncertainty in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Significant items subject to such estimates and assumptions include: • carrying amount of property and equipment; • carrying amount of goodwill and intangible assets; • leases; • estimates of claims accruals; • contingent obligations; • calculation of stock-based compensation; • valuation allowance for deferred income tax assets; • valuation allowances for receivables; and • valuation of financial instruments. Segments — The Company uses the "management approach" to determine its reportable segments, as well as to determine the basis of reporting the operating segment information. Certain of the Company's operating segments have been aggregated into reportable segments. The management approach focuses on financial information that management uses to make operating decisions. The Company's chief operating decision makers use total revenue, operating expense categories, operating ratios, operating income, and key operating statistics to evaluate performance and allocate resources to the Company's operations and is based around the transportation service offerings provided to the Company's customers, as well as the equipment utilized. Operating income is the measure that management uses to evaluate segment performance and allocate resources. Operating income should not be viewed as a substitute for GAAP net income. Management believes the presentation of operating income enhances the understanding of the Company's performance by highlighting the results of operations and the underlying profitability drivers of the business segments. Operating income is defined as "Total revenue" less "Total operating expenses." Based on the unique nature of the Company's operating structure, certain revenue-generating assets are interchangeable between segments. Additionally, the Company's chief operating decision makers do not review assets or liabilities by segment to make operating decisions. The Company allocates depreciation and amortization expense of its property and equipment to the segments based on the actual utilization of the asset by the segment during the period. See Note 25 for additional disclosures regarding the Company's segments. Cash and Cash Equivalents — Cash and cash equivalents are comprised of cash, money market funds, and highly liquid instruments with insignificant interest rate risk and original maturities of three months or less. Cash balances with institutions may be in excess of Federal Deposit Insurance Corporation ("FDIC") limits or may be invested in sweep accounts that are not insured by the institution, the FDIC, or any other government agency. Restricted Cash and Equivalents — The Company's wholly-owned captive insurance companies, Red Rock and Mohave, maintain certain operating bank accounts, working trust accounts, and investment accounts. The cash and cash equivalents within these accounts are restricted by insurance regulations to fund the insurance claim losses to be paid by the captive insurance companies, and therefore, are classified as "Cash and cash equivalents – restricted" and within "Other long-term assets" in the consolidated balance sheets. Restricted Investments — The Company's investments are restricted by insurance regulations to fund the insurance claim losses to be paid by the captive insurance companies. The Company accounts for its investments in accordance with ASC 320, Investments – Debt Securities . Management determines the appropriate classification of its investments in debt securities at the time of purchase and re-evaluates the determination on a quarterly basis. As of December 31, 2021, all of the Company's investments in fixed-maturity securities were classified as held-to-maturity, as the Company has the positive intent and ability to hold these securities to maturity. Held-to-maturity securities are carried at amortized cost. The amortized cost of debt securities is adjusted using the effective interest rate method for amortization of premiums and accretion of discounts. Amortization and accretion are reported in "Other income, net" in the consolidated statements of comprehensive income. Management periodically evaluates restricted investments for impairment. The assessment of whether impairments have occurred is based on management's case-by-case evaluation of the underlying reasons for the decline in estimated fair value. Management accounts for other-than-temporary impairments of debt securities in accordance with ASC 320. This guidance requires the Company to evaluate whether it intends to sell an impaired debt security or whether it is more likely than not that it will be required to sell an impaired debt security before recovery of the amortized cost basis. If either of these criteria are met, an impairment loss equal to the difference between the debt security's amortized cost and its estimated fair value is recognized in earnings. For impaired debt securities that do not meet these criteria, the Company determines if a credit loss exists with respect to the impaired security. If a credit loss exists, the credit loss component of the impairment (i.e., the difference between the security's amortized cost and the present value of projected future cash flows expected to be collected) is recognized in earnings and the remaining portion of the impairment is recognized as a component of accumulated other comprehensive income. See Note 5 for additional disclosures regarding the Company's restricted investments. Inventories and Supplies — Inventories and supplies, which are included in "Other current assets" in the consolidated balance sheets, primarily consist of spare parts, tires, fuel, and supplies and are stated at lower of cost or net realizable value. Depending on the class of inventory, cost is determined using the first-in, first-out method or average cost. Replacement tires held in the shops are classified as inventory and expensed when placed in service. Replacement tire costs incurred over the road are immediately expensed. Property and Equipment — Property and equipment is stated at cost less accumulated depreciation. Costs to construct significant assets include capitalized interest incurred during the construction and development period. Expenditures for replacements and improvements are capitalized. Maintenance and repairs are expensed as incurred. Net gains on the disposal of property and equipment are presented in the consolidated statements of comprehensive income within "Miscellaneous operating expenses." Tires on purchased revenue equipment are capitalized along with the related equipment cost when the vehicle is placed in service, and are depreciated over the life of the vehicle. Depreciation of property and equipment is calculated on a straight-line basis down to the salvage value, as applicable, over the following estimated useful lives: Category: Range (in years) Revenue equipment * 3 — 20 Shop and service equipment 2 — 10 Land improvements 5 — 15 Buildings and building improvements 10 — 40 Furniture and fixtures 3 — 10 Leasehold improvements Life of the lease *For finance leases involving revenue equipment, the depreciation period is equal to the term of the lease agreement. Management believes that these methods properly spread the costs over the useful lives of the assets. Management judgment is involved when determining estimated useful lives of the Company's long-lived assets. Useful lives of the Company's long-lived assets are determined based on historical experience, as well as future expectations regarding the period the Company expects to benefit from the asset. Factors affecting estimated useful lives of property and equipment may include estimating loss, damage, obsolescence, and Company policies around maintenance and asset replacement. Management evaluates its property and equipment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable in accordance with ASC 360, Property, Plant and Equipment . When such events or changes in circumstances occur, management performs a recoverability test that compares the carrying amount with the projected undiscounted cash flows from the use and eventual disposition of the asset or asset group. An impairment is recorded for any excess of the carrying amount over the estimated fair value. Fair value is determined through various valuation techniques including discounted cash flow models, quoted market values, and third-party independent appraisals, when necessary. Estimating fair value includes several significant assumptions, including future cash flow estimates, determination of appropriate discount rates, and other assumptions that management believes reasonable under the circumstances. Changes in these estimates and assumptions could materially affect the determination of fair value and/or impairment. Goodwill — Management evaluates goodwill on an annual basis as of June 30 th , or more frequently if indicators of impairment exist. The Company performs a quantitative analysis on an annual basis, in accordance with ASC 350, Goodwill and Other Intangible Assets . Management estimates the fair values of its reporting units using a combination of the income and market approaches. If the carrying amount of a reporting unit exceeds the fair value, then management recognizes an impairment loss of the same amount. This loss is only limited to the total amount of goodwill allocated to that reporting unit. Refer to Note 10 for the results of the Company's annual evaluation as of June 30, 2021. On a periodic basis, the Company assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than the carrying amount. If the Company concludes that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the Company conducts a quantitative goodwill impairment test. See Notes 4 and 10 for additional disclosures regarding the Company's goodwill. Intangible Assets other than Goodwill — The Company's intangible assets other than goodwill primarily consist of acquired customer relationships, trade names, and other intangibles from acquisitions. Amortization of acquired customer relationships, and other intangibles is calculated on a straight-line basis over the estimated useful life, which ranges from 3 years to 20 years. Certain trade names have indefinite useful lives and are not amortized, but are tested for impairment at least annually, unless events occur or circumstances change between annual tests that would more likely than not reduce the fair value. Management reviews its intangible assets for impairment whenever events or circumstances indicate that the carrying amount of the asset may not be recoverable, in accordance with ASC 350, Intangibles – Goodwill and Other. When such events or changes in circumstances occur, management performs a recoverability test that compares the carrying amount with the projected discounted cash flows from the use and eventual disposition of the asset or asset group. An impairment is recorded for any excess of the carrying amount over the estimated fair value, which is generally determined using discounted future cash flows. Fair value is determined through various valuation techniques, including discounted cash flow models, quoted market values, and third-party independent appraisals. Estimating fair value includes several significant assumptions, including future cash flow estimates, determination of appropriate discount rates, royalty rates, and other assumptions that management believes reasonable under the circumstances. Changes in these estimates and assumptions could materially affect the determination of fair value and/or impairment. See Notes 4 and 10 for additional disclosures regarding the Company's intangible assets. Claims Accruals — The Company is self-insured for a portion of its risk related to auto liability, workers' compensation, property damage, cargo damage, and group health. Self-insurance results from buying insurance coverage that applies in excess of a retained portion of risk for each respective line of coverage. The Company accrues for the cost of the uninsured portion of pending claims by evaluating the nature and severity of individual claims and by estimating future claims development based upon historical claims development trends. The actual cost to settle self-insured claim liabilities may differ from the Company's reserve estimates due to legal costs, claims that have been incurred but not reported, and various other uncertainties, including the inherent difficulty in estimating the severity of the claims and the potential judgment or settlement amount to dispose of the claim. See Notes 12 and 19 for additional disclosures regarding the Company's claims accruals. Leases — Management evaluates the Company’s leases based on the underlying asset groups. The assets currently underlying the Company’s leases include revenue equipment (primarily tractors and trailers), real estate (primarily buildings, office space, land, and drop yards), as well as technology and other equipment that supports business operations. Management’s significant assumptions and judgments include the determination of the discount rate (discussed below), as well as the determination of whether a contract contains a lease. In accordance with ASC 842, Leases , property and equipment held under operating leases are recorded as right-of-use assets, with a corresponding operating lease liability. Additionally, property and equipment held under finance leases are recorded as property and equipment with corresponding finance lease liabilities. All expenses related to operating leases are reflected in our consolidated statements of comprehensive income in "Rental expense." Expenses related to finance leases are reflected in our consolidated statements of comprehensive income in "Depreciation and amortization of property and equipment" and "Interest expense." • Lease Term — The Company’s leases generally have lease terms corresponding to the useful lives of the underlying assets. Revenue equipment leases have fixed payment terms based on the passage of time, which is typically three to five years for tractors and five to seven years for trailers. Certain finance leases for revenue equipment contain renewal or fixed price purchase options. Real estate leases, excluding drop yards, generally have varying lease terms between five and fifteen years and may include renewal options. Drop yards include month-to-month leases, as well as leases with varying lease terms generally ranging from two to five years. Options to renew or purchase the underlying assets are considered in the determination of the right-of-use asset and corresponding lease liability once reasonably certain of exercise. • Portfolio Approach — The Company typically leases its revenue equipment under master lease agreements, which contain general terms, conditions, definitions, representations, warranties, and other general language, while the specific contract provisions are contained within the various individual lease schedules that fall under a master lease agreement. Each individual leased asset within a lease schedule is similar in nature (i.e. all tractors or all trailers) and has identical contract provisions to all of the other individual leased assets within the same lease schedule (such as the contract provisions discussed above). Management has elected to apply the portfolio approach to its revenue equipment leases, as accounting for its revenue equipment under the portfolio approach would not be materially different from separately accounting for each individual underlying asset as a lease. Each individual real estate and other lease is accounted for at the individual asset level. • Nonlease Components — Management has elected to combine its nonlease components (such as fixed charges for common area maintenance, real estate taxes, utilities, and insurance) with lease components for each class of underlying asset, as applicable, as the nonlease components in the Company’s lease contracts typically are not material. These nonlease components are usually present within the Company’s real estate leases. The Company’s assets are generally insured by umbrella policies, in which the premiums change from one policy period to the next, making them variable in nature. Accordingly, these insurance costs are excluded from the Company’s calculation of right-of-use assets and corresponding lease liabilities. • Short-Term Lease Exemption — Management has elected to apply the short-term lease exemption to all asset groups. Accordingly, leases with terms of twelve months or less are not capitalized and continue to be expensed on a straight-line basis over the term of the lease. This primarily affects the Company’s drop yards and corresponding temporary structures on those drop yards. To a lesser extent, certain short-term leases for revenue equipment, technology, and other assets are affected. • Discount Rate — The Company uses the rate implicit in the lease, when readily determinable, which is generally related to the Company's finance leases. Otherwise the Company’s incremental borrowing rate is applied. The implicit interest rate is not readily determinable for the Company’s operating leases. As such, management applies the Company’s incremental borrowing rate, which is defined by GAAP as the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. The Company's incremental borrowing rate is based on the results of an independent third-party valuation. • Residual Values — The Company's finance leases for revenue equipment are typically structured with balloon payments at the end of the lease term equal to the residual value the Company is contracted to receive from certain equipment manufacturers upon sale or trade back to the manufacturers. If the Company does not receive proceeds of the contracted residual value from the manufacturer, the Company is still obligated to make the balloon payment at the end of the lease term. In connection with certain revenue equipment operating leases, the Company issues residual value guarantees, which provide that if the Company does not purchase the leased equipment from the lessor at the end of the lease term, then the Company is liable to the lessor for an amount equal to the shortage (if any) between the proceeds from the sale of the equipment and an agreed value. To the extent management believes any manufacturer will refuse or be unable to meet its obligation, the Company recognizes additional rental expense to the extent the fair market value at the lease termination is expected to be less than the obligation to the lessor. Proceeds from the sale of equipment under the Company’s operating leases generally exceed the payment obligation on substantially all operating leases. Although the Company typically owes certain amounts to its lessors at the end of its revenue equipment leases, the Company’s equipment manufacturers have corresponding guarantees back to the Company as to the buyback value of the units. See Note 16 for additional disclosures regarding the Company's leases. Fair Value Measurements — See Note 23 for accounting policies and financial information relating to fair value measurements. Contingencies — See Note 19 for accounting policies and financial information related to contingencies. Revenue Recognition — Management applies the five-step analysis to the Company's four reportable segments (Truckload, Logistics, LTL, and Intermodal). • Step 1: Contract Identification — Management has identified that a legally enforceable contract with its customers is executed by both parties at the point of pickup at the shipper's location, as evidenced by the bill of lading. Although the Company may have master agreements with its customers, these master agreements only establish general terms. There is no financial obligation to the shipper until the load is tendered/accepted and the Company takes possession of the load. • Step 2: Performance Obligations — The Company's only performance obligation is transportation services. The Company's delivery, accessorial, and dedicated operations truck capacity in its dedicated operations represent a bundle of services that are highly interdependent and have the same pattern of transfer to the customer. These services are not capable of being distinct from one another. For example, the Company generally would not provide accessorial services or truck capacity without providing delivery services. • Step 3: Transaction Price — Depending on the contract, the total transaction price may consist of mileage revenue, fuel surcharge revenue, accessorial fees, truck capacity, and/or non-cash consideration. Non-cash consideration is measured by the estimated fair value of the non-cash consideration at contract inception. There is no significant financing component in the transaction price, as the Company's customers generally pay within the contractual payment terms of 30 to 60 days. • Step 4: Allocating Transaction Price to Performance Obligations — The transaction price is entirely allocated to the only performance obligation: transportation services. • Step 5: Revenue Recognition — The performance obligation of providing transportation services is satisfied over time. Accordingly, revenue is recognized over time. Management estimates the amount of revenue in transit at period end based on the number of days completed of the dispatch (which is generally one to three days for the Truckload, Logistics and LTL segments, but can be longer for intermodal operations). Management believes this to be a faithful depiction of the transfer of services because if a load is dispatched, but terminates mid-route and the load is picked up by another carrier, then that carrier would not need to re-perform the services for the days already traveled. The Company outsources the transportation of loads to third-party carriers through its logistics operations. Management has determined that the Company is a principal in these arrangements, and therefore records revenue associated with these contracts on a gross basis. The Company has the primary responsibility to meet the customers' requirements. The Company invoices and collects from its customers and maintains discretion over pricing. Additionally, the Company is responsible for the selection of third-party transportation providers to the extent used to satisfy customer freight requirements. Significant judgments involved in the Company's revenue recognition and corresponding accounts receivable balances include: • Measuring in-transit revenue at period end (discussed above). • Estimating the allowance for doubtful accounts. The Company establishes an allowance for doubtful accounts based on historical experience and any known trends or uncertainties related to customer billing and account collectability. Management reviews the adequacy of its allowance for doubtful accounts on a quarterly basis. Uncollectible accounts are written off when deemed uncollectible, and accounts receivable are presented net of an allowance for doubtful accounts. • Contract Balances — In-transit revenue balances are included in "Contract balance – revenue in transit" in the consolidated balance sheets. The Company's contract liability balances are typically immaterial. • Revenue Disaggregation — In considering the level at which the Company should disaggregate revenues pertaining to contracts with customers, management determined that there are no significant differences between segments in how the nature, amount, timing, and uncertainty of revenue or cash flows are affected by economic factors. Additionally, management considered how and where the Company has communicated information about revenue for various purposes, including disclosures outside of the financial statements and how information is regularly reviewed by the Company's chief operating decision makers for evaluating financial performance of the Company's segments, among others. Based on these considerations, management determined that revenues should be disaggregated by reportable segment. The Company recognizes operating lease revenue from leasing tractors and related equipment to third parties, including independent contractors. Operating lease revenue from rental operations is recognized as earned, which is straight-lined per the rent schedules in the lease agreements. Losses from lease defaults are recognized as offsets to revenue. Stock-based Compensation — The Company accounts for stock-based compensation expense in accordance with ASC 718, Compensation – Stock Compensation. ASC 718 requires that all share-based payments to employees and non-employee directors, including grants of employee stock options, be recognized in the financial statements based upon a grant-date fair value of an award. Equity awards settled in cash are remeasured at each reporting period and are recognized as a liability in the consolidated balance sheets during the vesting period until settlement. • Fair Value — The fair value of performance units is estimated using the Monte Carlo Simulation valuation model. The fair value of stock options is estimated using the Black-Scholes option-valuation model. The fair value of restricted stock units is the closing stock price on the grant date. • Vesting — The requisite service period is the specified vesting date in the grant agreement or the date that the employee becomes retirement-eligible, based on the terms of the grant agreement. The Company calculates the number of awards expected to vest as awards granted, less expected forfeitures over the life of the award (estimated at grant date). All awards require future service and thus forfeitures are estimated based on historical forfeitures and the remaining term until the related award vests. Performance-based awards vest contingent upon meeting certain performance criteria established by the Company's compensation committee. • Expense — Awards that are only subject to time-vesting provisions are amortized using the straight-line method, by amortizing the grant-date fair value over the requisite service period of the entire award. Awards subject to time-based vesting and performance conditions are amortized using the individual vesting tranches. Unless a material deviation from the assumed forfeiture rate is observed during the term in which the awards are expensed, any adjustment necessary to reflect differences in actual experience is recognized in the period the award becomes payable or exercisable. Determining the appropriate amount to expense in each period is based on the likelihood and timing of achievement of the stated targets for performance-based awards, and requires judgment, including forecasting future financial results and market performance. The estimates are revised periodically, based on the probability and timing of achieving the required performance targets, and adjustments are made as appropriate. See Note 21 for additional information relating to the Company's stock-based compensation plan. Income Taxes — Management accounts for income taxes under the asset and liability method. Accordingly, deferred tax assets and liabilities are recognized for the future tax consequences of events that have been included in the consolidated financial statements. Additionally, deferred tax assets and liabilities are determined based on the differences between the financial statement carrying amounts and respective tax bases of assets and liabilities (using enacted tax rates in effect for the year in which the differences are expected to reverse). The effect on deferred tax assets and liabilities of changes in tax rates is recognized in income in the period that includes the enactment date. Net deferred incomes taxes are classified as noncurrent in the consolidated balance sheets. A valuation allowance is provided against deferred tax assets if the Company determines it is more likely than not that such assets will not ultimately be realized. In making such determinations, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies, and recent financial operations. To the extent management believes the likelihood of recovery is not sufficient, a valuation allowance is established for the amount determined not to be realizable. Management judgment is necessary in determining the frequency at which the need for a valuation allowance is assessed, the accounting period in which to establish the valuation allowance, as well as the amount of the valuation allowance. Unrecognized tax benefits are defined as the difference between a tax position taken or expected to be taken in a tax return and the benefit recognized and measured pursuant to ASC 740, Income Taxes . The Company does not recognize a tax benefit for uncertain tax positions unless it concludes that it is more likely than not that the benefit will be sustained on audit (including resolutions of any related appeals or litigation processes) by the taxing authority, based solely on the technical merits of the associated tax position. If the recognition threshold is met, the Company recognizes a tax benefit measured at the largest amount of the tax benefit that, in management's judgment, is greater than 50% likely to be realized. The Company records expected incurred interest and penalties related to unrecognized tax positions in "Income tax expense" in the consolidated statements of comprehensive income. To the extent interest and penalties are not assessed with respect to uncertain tax positions, amounts accrued will be reduced and reflected as a reduction of the overall income tax provision. Significant management judgment is required in determining the provision for income taxes and in determining whether deferred tax assets will be realized in full or in part. Management periodically assesses the likelihood that all or some portion of deferred tax assets will be recovered from future taxable income. Management judgment is also required regarding a variety of other factors including the appropriateness of tax strategies. The Company utilizes certain income tax planning strategies to reduce its overall income taxes. It is possible that certain strategies might be disallowed, resulting in an increased liability for income taxes. Significant management judgments are involved in assessing the likelihood of sustaining the strategies and determining the likely range of defense and settlement costs, in the event that tax strategies are challenged by taxing authorities. An ultimate result worse than the Company's expectations could adversely affect its results of operations. See Note 13 for additional disclosures regarding the Company's income taxes.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	12 Months Ended
	Dec. 31, 2021
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 October 2021 ASU No. 2021-08: Business Combinations (ASC 805), Accounting for Contract Assets and Contract Liabilities from Contracts with Customers The amendments in this ASU require that the acquirer recognize and measure contract assets and contract liabilities in a business combination in accordance with ASC 606 as if the acquirer had originated the contracts. The amendments in this ASU are applied prospectively to business combinations occurring on or after the effective date of the amendments. January 2023, Prospective Currently under evaluation, but not expected to be material August 2021 ASU No. 2021-06:Presentation of Financial Statements (ASC 205), Financial Services – Depository and Lending (ASC 942), and Financial Services – Investment Companies (ASC 946) 1 The ASU amends various SEC paragraphs pursuant to the issuance of an SEC release to update disclosure requirements for financial statements from acquired and disposed businesses including changes in tests and thresholds. Additionally, the ASU amends various SEC paragraphs pursuant to an SEC release to update statistical disclosure requirements for bank and savings and loan registrants. August 2021, Adoption method varies by amendment No material impact August 2020 ASU No. 2020-06: Debt – Debt with Conversion and Other Options (ASC 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (ASC 815-40) – Accounting for Convertible Instruments and contracts in an Entity's Own Equity The amendments in this ASU add disclosure requirements to convertible debt instruments and convertible preferred stock, require convertible instruments to be disclosed at fair value, and update the calculation requirements for diluted EPS. The amendments in this ASU can be applied on a modified or fully retrospective basis and are effective for public entities for years beginning after December 15, 2021. January 2022, Modified retrospective or fully retrospective No material impact 1 Adopted during the third quarter of 2021. Since management is continuing to evaluate the impacts of the above standards, disclosures around these preliminary assessments are subject to change.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2021
Business Combinations [Abstract]
Acquisitions	Acquisitions 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. The total purchase price consideration of $164.4 million, consisted of $104.0 million in cash consideration to the sellers, including cash on hand and net working capital adjustments, and approximately $60.4 million in debt payoffs. This was funded through cash-on-hand and borrowing on the 2021 Revolver on the transaction date. At closing, $2.8 million of the cash consideration was placed in escrow to secure certain of the sellers' indemnification obligations and remains subject to further adjustments. The purchase of the equity interests of MME results in the historical tax basis of MME's assets continuing to be recovered and any intangible assets arising through purchase accounting will result in additional stock basis for tax purposes. Deferred taxes were established as of the opening balance sheet for purchase accounting fair value adjustments (other than for goodwill). The SPA contains customary representations, warranties, covenants, and indemnification provisions. The goodwill recognized represents expected synergies from combining the operations of MME with the Company, including enhanced service offerings, as well as other intangible assets that did not meet the criteria for separate recognition. The goodwill is not expected to be deductible for tax purposes. ACT On July 5, 2021, the Company acquired 100.0% of Dothan, Alabama-based ACT. ACT is a leading LTL carrier that also offers dedicated contract carriage and ancillary services. The total purchase price consideration of $1.31 billion consisted of $1.30 billion in cash and $10.0 million in Knight-Swift shares issued to sellers at closing. Additionally, the Company assumed $36.5 million in debt, net of cash. Cash was funded from the July 2021 Term Loan, as well as existing Knight-Swift liquidity. ACT was an S corporation for tax purposes, and the transaction included an election under Internal Revenue Code Section 338(h)(10). Accordingly, the book and tax basis of the acquired assets and liabilities are the same as of the purchase date. The SPA contains customary representations, warranties, and covenants. The Company's consolidated financial statements for 2021 include ACT's operating results beginning July 5, 2021 (closing of the acquisition) through December 31, 2021. During 2021, the Company's consolidated operating results included ACT's total revenue of $386.8 million and net income of $23.1 million. ACT's net income during 2021 included $7.0 million related to the amortization of intangible assets acquired in the ACT Acquisition. The goodwill recognized represents expected synergies from combining the operations of ACT with the Company, including enhanced service offerings, as well as other intangible assets that did not meet the criteria for separate recognition. The goodwill is expected to be deductible for tax purposes. 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, the beginning of the comparative period presented. 2021 2020 (in thousands, except per share data) Total revenue $ 6,387,329 $ 5,374,934 Net income attributable to Knight-Swift 763,393 437,835 Earnings per share – diluted 4.57 2.57 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. As a result of the ACT Acquisition, the Company incurred certain acquisition-related expenses totaling $2.9 million in 2021. These expenses were eliminated in the presentation of the unaudited pro forma "Net income attributable to Knight-Swift" presented above. 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 an SPA, 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. The total purchase price consideration of $37.2 million, including cash-on-hand and net working capital adjustments, consisted of $32.2 million in cash to the sellers at closing, which was funded through cash-on-hand and borrowing on the 2017 Revolver on the transaction date. At closing $2.25 million of the cash consideration was placed in escrow to secure certain of the sellers' indemnification obligations and remains subject to further adjustments. The purchase price also included contingent consideration consisting of two additional annual payments of up to $2.5 million each ($5.0 million in total), representing the maximum possible annual deferred payments to the sellers based on operating ratio and revenue growth targets for each of the twelve-month periods ending May 31, 2022 and May 31, 2023. As of December 31, 2021, $2.5 million is included in "Accrued liabilities" and $2.5 million is included in "Other long-term liabilities" in the Company's consolidated balance sheets, depending on the expected payment dates. For income tax purposes, the sale of UTXL's equity interests to the Company is intended to be treated as a sale and purchase of assets. Accordingly, the book and tax basis of the acquired assets and liabilities are the same as of the purchase date. The SPA contains customary representations, warranties, covenants, and indemnification provisions. The goodwill recognized represents expected synergies from combining the operations of UTXL with the Company, including enhanced service offerings, as well as other intangible assets that did not meet the criteria for separate recognition. The goodwill is expected to be deductible for tax purposes. 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, a Greenville, South Carolina-based software provider, specializing in mobile driving platforms, which complement the Company's suite of services. The total purchase price consideration, including cash-on-hand and net working capital adjustments, consisted of $41.5 million in cash to the sellers at closing, which was funded through cash-on-hand and borrowing on the 2017 Revolver on the transaction date. At closing, $4.1 million of the cash consideration was placed in escrow to secure certain of the sellers' indemnification obligations and other items. The MIPA included that both the buyer and sellers would file an election under the Internal Revenue Code Section 754 to adjust the tax basis of the Company's assets and liabilities, with respect to the buyer's purchase of the equity. The MIPA contains customary representations, warranties, covenants, and indemnification provisions for transactions of this nature. The goodwill recognized represents expected synergies from combining the operations of Eleos with the Company, including enhanced service offerings, as well as other intangible assets that did not meet the criteria for separate recognition. The goodwill is expected to be deductible for tax purposes. Warehousing Co. On January 1, 2020, pursuant to a SPA the Company acquired 100.0% of the equity interests of Warehousing Co. with locations throughout the central US. The total purchase price consideration of $66.9 million consisted of $48.2 million in cash to the sellers at closing, which was funded through cash-on-hand and borrowing on the 2017 Revolver on the transaction date. At closing, $6.8 million of the cash consideration was placed in escrow to secure certain of the sellers' indemnification obligations. During the third quarter of 2020, the escrow proceeds were released to the sellers pursuant to the SPA. The purchase price also included contingent consideration consisting of three additional annual payments of up to $8.1 million each ($24.3 million in total), representing the maximum possible annual deferred payments to the sellers based on Warehousing Co.'s earnings before interest and taxes ("EBIT") for each of the calendar years ending December 31, 2020, December 31, 2021, and the annualized six-month period ending June 30, 2022. In order to estimate Warehousing Co.'s future performance, the Company utilized the Monte Carlo simulation method using certain inputs, including Warehousing Co.'s forecasted EBIT, discount rate, dividend yields, expected volatility, and expected stock returns during the above measurement periods. Based on the above inputs, the present value of the total contingent consideration, along with the estimated net working capital adjustment equaled $18.7 million as of January 1, 2020. During the measurement period, the net working capital adjustment was reduced by $0.4 million based on the actual versus estimated net working capital adjustment as of the transaction date. This adjustment resulted in the total estimated contingent consideration and net working capital adjustment decreasing to $18.3 million. The total purchase price consideration, as if adjusted at the January 1, 2020 transaction date, is identified in the "Purchase Price Allocations" table within this footnote. During the fourth quarter of 2020, the Company paid the first annual payment of $8.1 million as a result of the achievement of Warehousing Co.’s EBIT performance target for the calendar year December 31, 2020. Additionally, during the fourth quarter of 2020, the Company increased the estimated fair value of the remaining contingent consideration representing the final two annual payments, resulting in a $6.7 million fair value adjustment of the deferred earnout, which was recorded in “Miscellaneous operating expenses” in the consolidated statement of comprehensive income. During the fourth quarter of 2021, the Company paid the second annual payment of $8.1 million as a result of the achievement of Warehousing Co.’s EBIT performance target for the calendar year 2021. As of December 31, 2021, the remaining estimated contingent consideration was $8.1 million representing the fair value of the remaining annual deferred payments for the annualized six-month period ending June 30, 2022, all of which was recorded in "Accrued liabilities" in the consolidated balance sheets. As of December 31, 2020, the remaining contingent consideration was $16.2 million representing the fair value of the remaining annual deferred payments for the calendar year December 31, 2021 and the annualized six-month period ending June 30, 2022. As of December 31, 2020, $8.1 million of the total was recorded in "Accrued liabilities" in the consolidated balance sheets and the remaining $8.1 million was recorded in "Other long-term liabilities" in the consolidated balance sheets. The SPA included an election under the Internal Revenue Code Section 338(h)(10). Accordingly, the book and tax basis of the acquired assets and liabilities are the same as of the purchase date. The SPA contains customary representations, warranties, covenants, and indemnification provisions. The goodwill recognized represents expected synergies from combining the operations of Warehousing Co. with the Company, including enhanced service offerings, as well as other intangible assets that did not meet the criteria for separate recognition. The goodwill is expected to be deductible for tax purposes. Purchase Price Allocations The purchase price allocations for the Company's acquisitions are preliminary, except for Warehousing Co., and have been allocated based on estimated fair values of the assets acquired and liabilities assumed at the acquisition dates, 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 are not to exceed one year from the respective acquisition dates. MME ACT UTXL Eleos Warehousing Co. 1 December 6, 2021 Opening Balance Sheet as Reported at December 31, 2021 July 5, 2021 Opening Balance Sheet as Reported at December 31, 2021 June 1, 2021 Opening Balance Sheet as Reported at December 31, 2021 February 1, 2021 Opening Balance Sheet as Reported at December 31, 2021 January 1, 2020 Opening Balance Sheet as Reported at December 31, 2021 Fair value of the consideration transferred $ 164,382 $ 1,306,214 $ 37,230 $ 41,518 $ 66,444 Cash and cash equivalents 14,716 17,477 8,206 2,237 1,388 Trade receivables 21,915 104,220 9,451 545 3,301 Prepaid expenses 2,067 15,803 — 47 608 Other current assets 462 3,537 — — 78 Property and equipment 49,192 427,722 54 — 1,938 Operating lease right-of-use assets 52,065 4,053 — 560 12,356 Identifiable intangible assets 2 52,960 406,160 22,121 15,850 55,681 Other noncurrent assets 139 1,739 — — 458 Total assets 193,516 980,711 39,832 19,239 75,808 Accounts payable (7,681) (19,386) (14,183) (156) (347) Accrued payroll and payroll-related expenses (7,106) (33,411) (247) (605) — Accrued liabilities (544) (9,302) (69) (1,391) (644) Claims accruals – current and noncurrent portions (1,090) (40,958) (418) — — Operating lease liabilities – current and noncurrent portions (46,375) (4,052) — (560) (12,356) Long-term debt – current and noncurrent portions — (54,024) — — — Deferred tax liabilities (19,009) — — — — Other long-term liabilities (568) (4,243) — (475) — Total liabilities (82,373) (165,376) (14,917) (3,187) (13,347) Noncontrolling interest — — — (10,281) — Total stockholders' equity — — — (10,281) — Goodwill $ 53,239 $ 490,879 $ 12,315 $ 35,747 $ 3,983 1 See above for a description of the working capital adjustments made to Warehousing Co.'s purchase price allocation during the measurement period. 2 Includes $372.2 million in customer relationships ($250.8 million attributed to ACT), $2.0 million in noncompete agreements ($0.8 million attributed to ACT), $10.5 million in internally developed software ($6.5 million attributable to ACT), and $168.0 million in trade names ($148.1 million attributed to ACT).

Investments

Investments	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Restricted Investments, Held-to-Maturity	Investments The following table presents the cost or amortized cost, gross unrealized gains and temporary losses, and estimated fair value of the Company's restricted investments: December 31, 2021 Gross Unrealized Cost or Amortized Cost Gains Temporary Estimated Fair Value (In thousands) US corporate securities $ 5,866 $ — $ (7) $ 5,859 Restricted investments, held-to-maturity $ 5,866 $ — $ (7) $ 5,859 December 31, 2020 Gross Unrealized Cost or Amortized Cost Gains Temporary Estimated Fair Value (In thousands) US corporate securities $ 9,001 $ 2 $ (8) $ 8,995 Restricted investments, held-to-maturity $ 9,001 $ 2 $ (8) $ 8,995 As of December 31, 2021, the contractual maturities of the restricted investments were one year or less. There were eleven and sixteen securities that were in an unrealized loss position, all for less than twelve months as of December 31, 2021 and 2020, respectively. The Company did not recognize any impairment losses related to restricted investments during 2021, 2020, or 2019. Refer to Note 2 for the related accounting policy and Note 23 for additional information regarding fair value measurements of restricted investments.

Equity Investments

Equity Investments	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Equity Investments	Equity Investments Transportation Resource Partners Since 2003, the Company has entered into partnership agreements with entities that make privately-negotiated equity investments, including Transportation Resource Partners III, LP ("TRP III"), TRP Capital Partners, LP ("TRP IV"), TRP Capital Partners V, LP ("TRP V"), TRP CoInvest Partners, (NTI) I, LP ("TRP IV Coinvestment NTI"), TRP CoInvest Partners, (QLS) I, LP ("TRP IV Coinvestment QLS"), TRP Coinvest Partners, FFR I, LP ("TRP IV Coinvestment FFR"), and TRP Coinvest Partners V (PW) I, LP ("TRP V Coinvest"). In these agreements, the Company committed to invest in return for an ownership percentage. The following table presents ownership and commitment information for the Company's investments in TRP partnerships: December 31, 2021 Knight-Swift's Ownership Interest 1 Total Commitment (All Partners) Knight-Swift's Contracted Commitment Knight-Swift's Remaining Commitment (Dollars in thousands) TRP III – equity method investment 3 5 6.0 % $ 245,000 $ 15,000 $ 1,692 TRP IV – equity investment 2 4 4.2 % $ 116,065 $ 4,900 $ 654 TRP IV Coinvestment NTI – equity method investment 5 — % $ 120,000 $ 10,000 $ — TRP IV Coinvestment QLS – equity method investment 25.0 % $ 39,000 $ 9,735 $ — TRP IV Coinvestment FFR – equity method investment 5 7.4 % $ 66,555 $ 4,950 $ — TRP V - equity method investment 6 16.6 % $ 180,700 $ 30,000 $ 17,803 TRP V Coinvest - equity method investment 5 6 13.3 % $ 30,000 $ 4,000 $ — 1 The Company's share of the results is included within "Other income, net" in the consolidated statements of comprehensive income. 2 In accordance with ASC 321, Investments – Equity Securities , these investments are recorded at cost minus impairment. 3 Management anticipates that $1.7 million will be due in 2022. 4 Management anticipates that the following amounts will be due: $0.1 million in 2022, $0.1 million from 2023 through 2024, $0.5 million in 2025, and none thereafter. 5 The TRP III, TRP IV Coinvestments, TRP V, and TRP V Coinvest are unconsolidated majority interests. Management considered the criteria set forth in ASC 323, Investments – Equity Method and Joint Ventures , to establish the appropriate accounting treatment for these investments. This guidance requires the use of the equity method for recording investments in limited partnerships where the "so minor" interest is not met. As such, the investments are being accounted for under the equity method. Knight's ownership interest reflects its ultimate ownership of the portfolio companies underlying the TRP III, TRP IV Coinvestment NTI, TRP IV Coninvestment QLS, TRP IV Coinvestment FFR, TRP V, and TRP V Coninvest legal entities. 6 Management anticipates that the following amounts will be due: $7.2 million in 2022, $7.2 million from 2023 through 2024, $0.9 million from 2025 through 2026, and $2.5 million thereafter. Embark During the second quarter of 2021, the Company invested $25.0 million in Embark in exchange for a convertible note. The terms of the agreement provided that the amount outstanding on the convertible note would be automatically converted into a number of shares of Embark's common stock upon either the closing of a qualified financing or upon a public event, subject to discounted conversion pricing per share based on a valuation of Embark. In November 2021, Embark and Northern Genesis Acquisition Corp II, a publicly-traded special purpose acquisition company, completed a business combination agreement entered into on June 22, 2021, resulting in Embark becoming a publicly-traded company. In association with this transaction, the Company's convertible note automatically converted into a number of shares of Embark's common stock as outlined above. Further, the Company acquired an additional $25.0 million in Embark's common stock pursuant to a common stock subscription agreement between the Company and Embark. As of December 31, 2021, the fair value of the combined investment in Embark was $54.5 million, resulting in a net unrealized gain of $4.5 million recognized during 2021 in "Operating income, net" in the consolidated statements of comprehensive income. Other Equity Method Investments On October 1, 2020, the Company used approximately $39.6 million in cash to purchase 21.0% of the equity interests of a transportation-related company ("Holdings Co."), complementary to its suite of services. Based on Holdings Co.'s board of directors and the Company's minority rights, the Company has concluded that its investment allows it to exercise significant influence over the operational and financial decisions of Holdings Co. and therefore has recorded the transaction as an equity method investment. The carrying amount of the Company's initial investment in Holdings Co. was approximately $36.6 million in excess of the Company's initial underlying equity interest in the net assets in Holdings Co. This basis difference represents the Company's proportionate share of the fair value of Holdings Co.'s net tangible assets and its identified intangible assets, with the remaining excess recognized as equity method goodwill. The Company's proportionate share of certain identified definite-lived intangibles are amortized over their estimated useful lives and accreted against the earnings recognized from the Company's interest in Holdings Co. Net Investment Balances Net investment balances included in "Other long-term assets" in the consolidated balance sheets were as follows: December 31, 2021 2020 (in thousands) TRP III – equity method investment $ 801 $ 217 TRP IV – equity investment 1 3 2,952 TRP IV Coinvestment NTI – equity method investment 37 5,609 TRP IV Coinvestment QLS – equity method investment 12,444 16,240 TRP IV Coinvestment FFR – equity method investment 6,761 4,905 TRP V – equity method investment 12,043 3,304 TRP V Coinvest – equity method investment 4,859 4,000 Holdings Co. – equity method investment 2 38,821 40,335 Embark – equity investment $ 54,467 $ — Total carrying value $ 130,236 $ 77,562 1 In accordance with ASC 321, Investments – Equity Securities , these investments are recorded at cost minus impairment. 2 In accordance with ASC 323, Investments – Equity Method and Joint Ventures, the net investment balance includes accretion of amortization of certain definite-lived intangibles.

Trade Receivables, net

Trade Receivables, net	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Trades Receivables, net	Trade Receivables, net Trade receivables, net balances were comprised of the following: December 31, 2021 2020 (In thousands) Trade customers $ 847,305 $ 570,611 Equipment manufacturers 11,923 5,680 Insurance premiums 1 43,455 5,804 Other 1 30,316 18,477 Trade receivables 932,999 600,572 Less: Allowance for doubtful accounts (21,663) (22,093) Trade receivables, net $ 911,336 $ 578,479 1 Prior year amounts within the table above have been reclassified to conform to current year presentation. The following is a rollforward of the allowance for doubtful accounts for trade receivables: 2021 2020 2019 (In thousands) Beginning balance $ 22,093 $ 18,178 $ 16,355 Provision 10,900 17,267 16,925 Write-offs directly against the reserve (776) (902) (2,652) Write-offs for revenue adjustments (11,504) (12,450) (12,450) Other 1 950 — — Ending balance $ 21,663 $ 22,093 $ 18,178 1 Represents allowance for doubtful trade accounts receivables assumed in 2021 from the Company's acquisitions. See Note 4 for further details regarding these acquisitions. See Note 14 for a discussion of the Company's accounts receivable securitization program and the related accounting treatment. The Company provides financing to independent contractors and other third parties on equipment sold or leased. Most of the notes are collateralized and are due in weekly installments, including principal and interest payments, ranging from 5.1% to 15.0%. Notes receivable are included in "Other current assets" and "Other long-term assets" in the consolidated balance sheets and were comprised of: December 31, 2021 2020 (In thousands) Notes receivable from independent contractors $ 5,969 $ 7,291 Convertible note receivable from third party 10,141 — Notes receivable from other third parties 994 3,034 Gross notes receivable 17,104 10,325 Allowance for doubtful notes receivable (496) (602) Total notes receivable, net of allowance $ 16,608 $ 9,723 Current portion, net of allowance 1,848 2,846 Long-term portion $ 14,760 $ 6,877 Convertible Note

Notes Receivable, net

Notes Receivable, net	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Notes Receivable, net	Trade Receivables, net Trade receivables, net balances were comprised of the following: December 31, 2021 2020 (In thousands) Trade customers $ 847,305 $ 570,611 Equipment manufacturers 11,923 5,680 Insurance premiums 1 43,455 5,804 Other 1 30,316 18,477 Trade receivables 932,999 600,572 Less: Allowance for doubtful accounts (21,663) (22,093) Trade receivables, net $ 911,336 $ 578,479 1 Prior year amounts within the table above have been reclassified to conform to current year presentation. The following is a rollforward of the allowance for doubtful accounts for trade receivables: 2021 2020 2019 (In thousands) Beginning balance $ 22,093 $ 18,178 $ 16,355 Provision 10,900 17,267 16,925 Write-offs directly against the reserve (776) (902) (2,652) Write-offs for revenue adjustments (11,504) (12,450) (12,450) Other 1 950 — — Ending balance $ 21,663 $ 22,093 $ 18,178 1 Represents allowance for doubtful trade accounts receivables assumed in 2021 from the Company's acquisitions. See Note 4 for further details regarding these acquisitions. See Note 14 for a discussion of the Company's accounts receivable securitization program and the related accounting treatment. The Company provides financing to independent contractors and other third parties on equipment sold or leased. Most of the notes are collateralized and are due in weekly installments, including principal and interest payments, ranging from 5.1% to 15.0%. Notes receivable are included in "Other current assets" and "Other long-term assets" in the consolidated balance sheets and were comprised of: December 31, 2021 2020 (In thousands) Notes receivable from independent contractors $ 5,969 $ 7,291 Convertible note receivable from third party 10,141 — Notes receivable from other third parties 994 3,034 Gross notes receivable 17,104 10,325 Allowance for doubtful notes receivable (496) (602) Total notes receivable, net of allowance $ 16,608 $ 9,723 Current portion, net of allowance 1,848 2,846 Long-term portion $ 14,760 $ 6,877 Convertible Note

Assets Held for Sale

Assets Held for Sale	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment Assets Held-for-sale Disclosure [Abstract]
Assets Held for Sale	Assets Held for Sale The Company expects to sell its assets held for sale within the next twelve months. Revenue equipment held for sale totaled $8.2 million and $29.8 million as of December 31, 2021 and 2020, respectively. Net gains on disposals, including disposals of property and equipment classified as assets held for sale, reported in "Miscellaneous operating expenses" in the consolidated statements of comprehensive income were $74.8 million during 2021, $9.7 million during 2020, and $32.9 million during 2019. During 2021 , the Company incurred impairment losses of $0.3 million, primarily related to certain legacy trailer models. During 2020, t he Company incurred impairment losses of $0.5 million, primarily related to certain tractors and trailers as a result of a softer used equipment market. During 2019 , the Company incurred impairment losses of $0.4 million primarily related to certain legacy trailer models as a result of a softer used equipment market.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill The changes in the carrying amounts of goodwill were as follows: 2021 2020 2019 (In thousands) Goodwill at beginning of period $ 2,922,964 $ 2,918,992 $ 2,919,176 Amortization relating to deferred tax assets (9) (11) (232) Acquisitions 1 592,180 3,983 48 Goodwill at end of period $ 3,515,135 $ 2,922,964 $ 2,918,992 1 The goodwill associated with the ACT and MME acquisitions was allocated to the LTL segment. The goodwill associated with the UTXL acquisition was allocated to the Logistics segment. The goodwill associated with the Warehousing Co, and Eleos acquisitions was allocated to the non-reportable segments. See Note 4 regarding the amount attributed to adjustments to the opening balance sheets. The following presents the components of goodwill by reportable segment as of December 31, 2021 and 2020: December 31, 2021 2020 Net Carrying Amount 1 Net Carrying Amount 1 (In thousands) Truckload $ 2,658,086 $ 2,658,095 Logistics 54,827 42,512 LTL 544,118 — Intermodal 175,594 175,594 Non-reportable 82,510 46,763 Goodwill $ 3,515,135 $ 2,922,964 1 Except for the net accumulated amortization related to deferred tax assets in the Truckload segment, the net carrying amount and gross carrying amount are equal since there are no accumulated impairment losses. There were no impairments identified during annual goodwill impairment testing in 2021, 2020, or 2019. Other Intangible Assets Other intangible asset balances were as follows: December 31, 2021 2020 (In thousands) Definite-lived intangible assets: 1 Gross carrying amount $ 1,227,630 $ 894,597 Accumulated amortization (201,139) (145,852) Definite-lived intangible assets, net 1,026,491 748,745 Indefinite-lived trade names: Gross carrying amount 804,558 640,500 Intangible assets, net $ 1,831,049 $ 1,389,245 1 The major categories of the Company's definite-lived intangible assets include customer relationships, non-compete agreements, internally-developed software, trade names, and others. Identifiable intangible assets subject to amortization have been recorded at fair value. Intangible assets related to acquisitions other than the 2017 Merger are amortized over a weighted-average amortization period of 19.0 years. The Company's customer relationship intangible assets related to the 2017 Merger are being amortized over a weighted average amortization period of 19.9 years. The following table presents amortization of intangible assets related to the 2017 Merger and various acquisitions: 2021 2020 2019 (In thousands) Amortization of intangible assets related to the 2017 Merger $ 41,375 $ 41,375 $ 41,375 Amortization related to other intangible assets 13,924 4,520 1,501 Amortization of intangibles $ 55,299 $ 45,895 $ 42,876 As of December 31, 2021, management anticipates that the composition and amount of amortization associated with intangible assets will be $64.7 million in 2022, $64.2 million for each of the years 2023 and 2024, $64.1 million in 2025, and $62.7 million in 2026. Actual amounts of amortization expense may differ from estimated amounts due to additional intangible asset acquisitions, impairment of intangible assets, accelerated amortization of intangible assets, and other events. See Note 2 for accounting policies regarding goodwill and other intangible assets.

Accrued Payroll and Purchased T

Accrued Payroll and Purchased Transportation	12 Months Ended
	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued Payroll and Purchased Transportation	Accrued Payroll and Purchased Transportation The following table presents the composition of accrued payroll and purchased transportation: December 31, 2021 2020 (In thousands) Accrued payroll 1 $ 146,326 $ 114,835 Accrued purchased transportation 70,758 46,053 Accrued payroll and purchased transportation $ 217,084 $ 160,888 1 Accrued payroll includes accruals related to the various 401(k) plans the Company offers to its employees. Depending on the plan, employees must meet the minimum age requirement (18 – 21 years) and have completed ninety days or one year of service with the Company in order to qualify. Employees' rights to employer contributions are fully vested after three or five years from their date of employment. The plans offer discretionary matching contributions of the greater of 100% up to 3.0% or 6.0% of an employee's eligible compensation or $2,000. The Company's employee benefits expense for matching contributions related to the 401(k) plans was approximately $16.2 million, $13.6 million, and $8.8 million in 2021, 2020, and 2019, respectively. This expense was included in "Salaries, wages, and benefits" in the consolidated statements of comprehensive income. As of December 31, 2021 and 2020, the balance above in accrued payroll included $14.5 million and $12.8 million, respectively, in matching contributions for the 401(k) plans.

Claims Accruals

Claims Accruals	12 Months Ended
	Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Abstract]
Claims Accruals	Claims Accruals Claims accruals represent the uninsured portion of outstanding claims at year-end. The current portion reflects the amount of claims expected to be paid in the following year. The Company's insurance programs for workers' compensation, auto and collision liability, physical damage, third-party carrier and independent contractor claims, cargo damage, and medical involves self-insurance with varying risk retention levels. Claims accruals were comprised of the following: December 31, 2021 2020 (In thousands) Auto reserves $ 263,091 $ 231,875 Workers’ compensation reserves 90,481 94,609 Third-party carrier claims reserves 31,524 40 Independent contractor claims reserves 6,285 7,112 Cargo damage reserves 5,409 2,494 Employee medical and other reserves 20,531 13,612 Claims accruals 417,321 349,742 Less: current portion of claims accruals (206,607) (174,928) Claims accruals, less current portion $ 210,714 $ 174,814 Self Insurance Automobile Liability, General Liability, and Excess Liability — Effective November 1, 2020, the Company has $100.0 million in excess auto liability ("AL") coverage. Effective November 1, 2019, the Company had $130.0 million in excess AL coverage. For prior years, Swift and Knight separately maintained varying excess AL and general liability limits. During prior policy periods, Swift AL claims were subject to a $10.0 million self-insured retention ("SIR") per occurrence and Knight AL claims were subject to a $1.0 million to $3.0 million SIR per occurrence. Additionally, Knight carried a $2.5 million aggregate deductible for any loss or losses within the $5.0 million excess of $5.0 million layer of coverage. Effective March 1, 2020, Knight and Swift retain the same $10.0 million SIR per occurrence. Workers' Compensation and Employers' Liability — The Company is self-insured for workers' compensation coverage. Swift maintains statutory coverage limits, subject to a $5.0 million SIR for each accident or disease. Effective March 1, 2019, Knight maintains statutory coverage limits, subject to a $2.0 million SIR for each accident or disease. Prior to March 1, 2019, the Knight SIR was $1.0 million per each accident or disease. Cargo Damage and Loss — The Company is insured against cargo damage and loss with liability limits of $2.0 million per truck or trailer with a $15.0 million limit per occurrence. Medical — Knight maintains primary and excess coverage for employee medical expenses, with a $0.4 million SIR per claimant. Through December 31, 2019, Swift was fully insured on its medical benefits (subject to contributed premiums). Effective January 1, 2020, Swift provides primary and excess coverage for employee medical expenses, with an SIR of $0.5 million per claimant to all employees. ACT — ACT maintains SIRs for claims on cargo losses, employee health and welfare, bodily injury and property, general liability and workers’ compensation. Losses under the employee health and welfare, BIPD, and workers’ compensation programs are typically limited on a per claim and aggregate basis through stop-loss and excess insurance policies. Risk retention amounts per occurrence are as follows: • Workers' compensation - $1.0 million • Auto liability - $2.0 million (ACT maintains a $5.0 million annual corridor deductible subject to a $10.0 million three-year policy term aggregate cap.) • Employee medical - $1.0 million. See Note 2 for accounting policy regarding the Company's claims accruals.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents the Company's income tax expense: 2021 2020 2019 (In thousands) Current expense: Federal $ 140,258 $ 80,060 $ 50,703 State 42,319 19,153 16,616 Foreign 8,382 4,248 5,526 190,959 103,461 72,845 Deferred expense (benefit): Federal 48,874 29,640 28,618 State (10,369) 7,292 3,712 Foreign 1,423 9,283 (1,377) 39,928 46,215 30,953 Income tax expense $ 230,887 $ 149,676 $ 103,798 Rate Reconciliation — Expected tax expense is computed by applying the US federal corporate income tax rate of 21.0% to earnings before income taxes for 2021, 2020 and 2019. Actual tax expense differs from expected tax expense as follows: 2021 2020 2019 (In thousands) Computed "expected" tax expense $ 204,673 $ 117,665 $ 86,935 Increase (decrease) in income taxes resulting from: State income taxes, net of federal income tax benefit 23,063 22,423 17,803 Other 3,151 9,588 (940) Income tax expense $ 230,887 $ 149,676 $ 103,798 Deferred Income Taxes — The components of the net deferred tax asset (liability) included in "Deferred tax liabilities" in the consolidated balance sheets were: December 31, 2021 2020 (In thousands) Deferred tax assets: Claims accrual $ 79,496 $ 81,426 Allowance for doubtful accounts 5,530 5,727 Amortization of stock options 8,192 7,712 Accrued liabilities 11,497 17,941 Operating lease liabilities 34,260 29,278 Other 20,562 10,687 Total deferred tax assets 159,537 152,771 Valuation allowance — — Total deferred tax assets, net 159,537 152,771 Deferred tax liabilities: Property and equipment, principally due to differences in depreciation (635,877) (586,349) Prepaid taxes, licenses, and permits deducted for tax purposes (15,241) (12,629) Intangible assets (338,191) (334,618) Operating lease right-of-use assets (34,016) (28,259) Other (11,089) (6,857) Total deferred tax liabilities (1,034,414) (968,712) Deferred income taxes $ (874,877) $ (815,941) 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 like ly than not that the results of future operations will generate sufficient taxable income to realize the deferred tax assets. All other deferred tax assets are expected to be realized and utilized by continued profitability in future periods. Cumulative Undistributed Foreign Earnings — As of December 31, 2021, foreign withholding taxes have not been provided on approximately $107.0 million of cumulative undistributed earnings of foreign subsidiaries. The earnings are considered to be permanently reinvested outside the US. As such, the Company is not required to provide withholding taxes on these earnings until they are repatriated in the form of dividends or otherwise. During the fourth quarter of 2020 our Mexico subsidiary distributed/repatriated $23.0 million to the US company. The taxes that resulted were insignificant. Unrecognized Tax Benefits — The Company's unrecognized tax benefits as of December 31, 2021 would favorably impact the Company's effective tax rate if subsequently recognized. See Note 2 for accounting policy related to the Company's income taxes. A reconciliation of the beginning and ending amounts of unrecognized tax benefits for 2021, 2020, and 2019 is below: 2021 2020 2019 (In thousands) Unrecognized tax benefits at beginning of year $ 2,950 $ 4,083 $ 7,423 Increases for tax positions taken prior to beginning of year — — 38 Decreases for tax positions taken prior to beginning of year (1,215) (1,133) (3,378) Unrecognized tax benefits at end of year $ 1,735 $ 2,950 $ 4,083 Increases for tax positions are related to the benefit received for federal deductions taken on the Company's subsidiary amended returns. Decreases for tax positions are related to federal deductions, which were reserved according to ASC 740-10. Management expects a decrease of $0.3 million in unrecognized tax benefits during the next twelve months. Interest and Penalties — Accrued interest and penalties were approximately $0.1 million and $0.3 million as of December 31, 2021 and December 31, 2020, respectively. 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 2016 remain subject to examination.

Accounts Receivable Securitizat

Accounts Receivable Securitization	12 Months Ended
	Dec. 31, 2021
Transfers and Servicing of Financial Assets [Abstract]
Accounts Receivable Securitization	Accounts Receivable Securitization On April 23, 2021, the Company entered into the 2021 RSA which further amended the 2018 RSA. The 2021 RSA is a secured borrowing that is collateralized by the Company's eligible receivables, for which the Company is the servicing agent. The Company's receivable originator subsidiaries sell, on a revolving basis, undivided interests in all of their eligible accounts receivable to Swift Receivables Company II, LLC ("SRCII") who in turn sells a variable percentage ownership in those receivables to the various purchasers. The Company's eligible receivables are included in "Trade receivables, net of allowance for doubtful accounts" in the consolidated balance sheets. As of December 31, 2021, the Company's eligible receivables 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 December 31, 2021. 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 and 2018 RSA (dollars in thousands): 2021 RSA 2018 RSA (Dollars in thousands) Effective April 23, 2021 July 11, 2018 Final maturity date April 23, 2024 July 9, 2021 Borrowing capacity $400,000 $325,000 Accordion option 1 $100,000 $175,000 Unused commitment fee rate 2 20 to 40 basis points 20 to 40 basis points Program fees on outstanding balances 3 4 one month LIBOR + 82.5 basis points one month LIBOR + 80 to 100 basis points 1 The accordion option increases the maximum borrowing capacity, subject to participation by the purchasers. 2 The 2021 RSA and 2018 RSA commitment fee rates are based on the percentage of the maximum borrowing capacity utilized. 3 Only the rate for the 2018 RSA program fee is subject to the Company's consolidated total net leverage ratio. 4 As identified within the 2021 RSA, the lender can trigger an amendment by identifying and deciding upon a replacement index for LIBOR. Availability under the 2021 RSA and 2018 RSA is calculated as follows: December 31, 2021 2020 (In thousands) Borrowing base, based on eligible receivables $ 400,000 $ 302,700 Less: outstanding borrowings 1 (279,000) (214,000) Less: outstanding letters of credit (65,300) (67,281) Availability under accounts receivable securitization facilities $ 55,700 $ 21,419 1 As of December 31, 2021, outstanding borrowings are included in "Accounts receivable securitization – less current portion" in the consolidated balance sheets and are offset by $0.5 million of deferred loan costs. As of December 31, 2020, outstanding borrowings are included in "Accounts receivable securitization – current portion" in the consolidated balance sheets and are offset by $0.1 million of deferred loan costs. Interest accrued on the aggregate principal balance at a rate of 0.9% and 1.0%, as of December 31, 2021 and 2020, respectively. Program fees and unused commitment fees are recorded in "Interest expense" in the consolidated statements of comprehensive income. The Company's accounts receivable securitization incurred program fees of $3.1 million in 2021, $3.5 million in 2020, and $7.2 million in 2019. Refer to Note 23 for information regarding the fair value of the 2021 RSA and 2018 RSA.

Debt And Financing

Debt And Financing	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Debt And Financing	Debt and Financing Other than the Company's accounts receivable securitization as discussed in Note 14 and its outstanding finance lease obligations as discussed in Note 16, the Company's long-term debt consisted of the following: December 31, 2021 2020 (In thousands) 2021 Term Loan A-1, due December 3 2022, net 1 2 $ 199,676 $ — 2021 Term Loan A-2, due September 3, 2024, net 1 2 199,607 — 2021 Term Loan A-3, due September 3, 2026, net 1 2 798,352 — 2017 Term Loan, due October 2022, net 1 3 — 298,907 Prudential Notes, net 1 47,265 — Other 5,069 — Total long-term debt, including current portion 1,249,969 298,907 Less: current portion of long-term debt (212,417) — Long-term debt, less current portion $ 1,037,552 $ 298,907 December 31, 2021 2020 (In thousands) Total long-term debt, including current portion $ 1,249,969 $ 298,907 2021 Revolver, due September 3, 2026 1 4 260,000 — 2017 Revolver, due October 2022 1 5 — 210,000 Long-term debt, including revolving line of credit $ 1,509,969 $ 508,907 1 Refer to Note 23 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 $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 3 Net of $1.1 million in deferred loan costs at December 31, 2020. 4 The Company also had outstanding letters of credit of $64.0 million under the 2021 Revolver, primarily related to workers' compensation and self-insurance liabilities, at December 31, 2021. 5 The Company also had outstanding letters of credit of $29.3 million under the 2017 Revolver, primarily related to workers' compensation and self-insurance liabilities, at December 31, 2020. 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 (described below). 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 margin reference rate 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 Loan and 2021 Revolver is based on the Company's consolidated leverage ratio. As of December 31, 2021, interest accrued at 1.022% on the 2021 Term Loans and 1.064% 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 0.07% to 0.20%. As of December 31, 2021, commitment fees on the unused portion of the 2021 Revolver accrued at 0.100% and outstanding letter of credit fees accrued at 1.000%. 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 December 31, 2021, 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 material domestic subsidiaries (other than its captive insurance subsidiaries, driving academy subsidiary, and bankruptcy-remote special purpose subsidiary). July 2021 Term Loan — On July 6, 2021, Knight-Swift entered into a $1.2 billion term loan with Bank of America, N.A (the "July 2021 Term Loan"). The July 2021 Term Loan was incremental to, and was separate from, the 2017 Debt Agreement. The July 2021 Term Loan was fully funded on July 6, 2021 and there were no scheduled principal payments prior to its scheduled maturity in October 2022. The interest rate applicable to the July 2021 Term Loan was subject to a leverage-based grid and equaled the BSBY rate plus 1.000% at closing. The July 2021 Term Loan was paid off and terminated using the proceeds of the 2021 Term Loans, discussed above. The July 2021 Term Loan contained similar terms to the 2017 Debt Agreement, including the financial covenants, usual and customary events of default for a facility of this nature, and certain usual and customary restrictions and covenants. ACT Credit Agreement Prudential Notes — Through the acquisition of ACT, the Company assumed the S econd Amended and Restated Note Purchase and Private Shelf Agreement with Prudential Capital Group ("2014 Prudential Notes"). On September 3, 2021, ACT entered into the 2021 Prudential Notes, replacing the 2014 Prudential Notes. The 2021 Prudential Notes have interest rates ranging from 4.05% to 4.40% and various maturity dates ranging from October 2023 through January 2028. 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 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 December 31, 2021 , ACT had $77.6 million available under the agreement. See Note 23 for fair value disclosures regarding the Company's debt instruments.

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	Leases Lessee Disclosures Lease Cost — The components of the Company's lease cost were as follows: 2021 2020 (in thousands) Operating lease cost: Operating lease costs $ 46,795 $ 80,456 Short-term lease cost ¹ 8,426 6,544 Sublease income (60) (360) Rental expense 55,161 86,640 Finance lease cost: Amortization of property and equipment 37,659 16,638 Interest expense 5,232 2,896 Total finance lease cost 42,891 19,534 Total operating and finance lease costs $ 98,052 $ 106,174 1 Short-term lease cost includes leases with a term of twelve months or less, as well as month-to-month leases and variable lease costs. Lease Liability Calculation Assumptions — The assumptions underlying the calculation of the Company's right-of-use assets and corresponding lease liabilities are disclosed below. December 31, 2021 2020 Operating Finance Operating Finance Revenue equipment leases Weighted average remaining lease term 1.6 years 4.0 years 2.0 years 3.6 years Weighted average discount rate 2.3 % 1.9 % 2.4 % 2.4 % Real estate and other leases Weighted average remaining lease term 12.6 years — 10.6 years — Weighted average discount rate 3.0 % — % 3.7 % — % Maturity Analysis of Lease Liabilities (as Lessee) — Future minimum lease payments for all noncancelable leases were: December 31, 2021 Operating Finance (In thousands) 2022 $ 38,871 $ 54,741 2023 27,124 49,275 2024 15,084 91,115 2025 11,037 70,543 2026 8,793 9,839 Thereafter 71,007 45,185 Future minimum lease payments 171,916 320,698 Less: amounts representing interest (28,980) (14,526) Present value of minimum lease payments 142,936 306,172 Less: current portion (35,322) (50,006) Lease liabilities – less current portion $ 107,614 $ 256,166 Supplemental Cash Flow Lease Disclosures — The following table sets forth cash paid for amounts included in the measurement of lease liabilities: 2021 2020 (in thousands) Operating cash flows for operating leases $ 48,171 $ 83,675 Operating cash flows for finance leases 5,232 2,896 Financing cash flows for finance leases 108,186 83,910 Refer to Note 24 for information regarding the leasing transactions between the Company and its related parties. Lessor Disclosures The Company leases revenue equipment to independent contractors and other third parties under operating leases, which generally have terms between three and four years, and include renewal and purchase options. These leases also include variable charges associated with miles driven in excess of the stipulated allowable miles in the contract, which are accounted for separately and presented in the table below. Lease classification is determined based on minimum rental receipts per the agreement, including residual value guarantees, when applicable, as well as receivables due to the Company upon default or cross-default. When independent contractors default on their leases, the Company typically re-leases the equipment to other independent contractors. As such, future lease receipts reflect original leases and re-leases. The Company's leases to third parties, some of which are subleases, are generally short-term, and may include renewal options. The owned assets underlying the Company's leases as lessor primarily consist of revenue equipment. As of December 31, 2021 and 2020, the gross carrying value of such revenue equipment underlying these leases was $103.2 million and $103.1 million, respectively, and accumulated depreciation was $40.0 million and $29.7 million, respectively. Depreciation is calculated on a straight-line basis down to the residual value, as applicable, over the estimated useful life of the equipment. Depreciation expense for these assets was $20.6 million for 2021 and 2020. Additionally, the Company periodically leases or subleases out real estate for use by third parties. These leases have varying terms, and may include renewal options. Management’s significant assumptions and judgments include the determination of the amount the Company expects to derive from the underlying asset at the end of the lease term, as well as whether a contract contains a lease. Lease Revenue and Rental Income — The components of the Company's lease revenue are included in "Revenue, excluding truckload and LTL fuel surcharge" and the Company's rental income is included in "Other income, net" in the consolidated statements of comprehensive income. These amounts are disclosed in the table below. 2021 2020 (in thousands) Operating lease revenue $ 95,934 $ 45,698 Variable lease revenue 1,353 1,691 Total lease revenue 1 $ 97,287 $ 47,389 Rental income 2 $ 10,375 $ 10,365 1 Represents operating revenue earned by the Company for leasing equipment to independent contractors and other third-parties. 2 Represents non-operating income earned from leasing real estate to third parties. Maturity Analysis of Future Lease Revenues (as Lessor) — Future minimum lease revenues for all noncancelable leases were: December 31, 2021 (In thousands) 2022 $ 38,262 2023 26,211 2024 12,492 2025 5,215 2026 1,926 Thereafter 3,618 Future minimum lease revenues $ 87,724 Refer to Note 24 for information regarding the leasing transactions between the Company and related parties.

Defined Benefit Pension Plan

Defined Benefit Pension Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Defined Benefit Plan	Defined Benefit Pension Plan Through the ACT Acquisition, the Company assumed a defined benefit pension plan covering ACT's drivers, drivers' helpers, warehousemen, warehousemen's helpers, mechanics, and mechanics' helpers. The plan provides normal retirement benefits based on years of credited service and applicable benefit units as defined by the plan. Provision is also made for early and defined retirements. The pension plan was amended such that benefit accrual and plan participation for the plan were effectively frozen as of January 1, 1997, resulting in a curtailment on that date. The net pension liability recognized is as follows: December 31, 2021 (In thousands) Projected benefit obligation $ 71,440 Less: fair value of plan assets 70,467 Unfunded status $ 973 Accrued pension liability recognized 1 $ 973 1 The pension liability is included in "Other long-term liabilities" in the consolidated balance sheets. "Other comprehensive loss" in the consolidated statements of comprehensive income included a $0.6 million loss from pension plan adjustments during 2021. The provisions of the plan do not require compensation levels to be considered in determining the plan’s benefit obligation. As such, the accumulated benefit obligation and projected benefit obligation are the same. Other information concerning the defined benefit pension plan is summarized below: 2021 (In thousands) Net periodic pension income $ 1,483 Benefits paid 2,981 Assumptions A weighted-average discount rate of 2.53% was used to determine benefit obligations as of December 31, 2021. The following weighted-average assumptions were used to determine net periodic pension cost: 2021 Discount rate 2.55 % Expected long-term rate of return on pension plan assets 6.00 % ACT's assumptions for the expected long-term rate of return on pension plan assets are based on a periodic review of the plan’s asset allocation over a long-term period. Expectations of returns for each asset class are based on comprehensive reviews of historical data and economic/financial market theory. The expected long-term rate of return on pension plan assets was selected from within the reasonable range of rates determined by (1) historical real returns, net of inflation, for the asset classes covered by the investment policy and (2) projections of inflation over the long-term period during which benefits are payable to plan participants. The defined benefit pension plan weighted-average asset allocations, by asset category, are as follows: 2021 Asset category: Equity securities 30 % Debt securities 68 % Cash and cash equivalents 2 % Total 100 % Pension plan assets The target allocation by asset category, is as follows: 2021 Asset category: Equity securities 30 % Debt securities 70 % Total 100 % The investment policy includes various guidelines and procedures designed to ensure assets are invested in a manner necessary to meet expected future benefit payments. The investment guidelines consider a broad range of economic conditions. Central to the policy are target allocation percentages (shown above) by major asset categories. The objectives of the target allocation percentages are to maintain investment portfolios that diversify risk through prudent asset allocation parameters and achieve asset returns that meet or exceed the plan’s actuarial assumptions. Refer to Note 23 for additional information regarding fair value measurements of the Company's investments. Cash flows ACT did not contribute to the pension plan during 2021. ACT is not expecting to recognize any net loss within "Other comprehensive loss" in the consolidated statements of comprehensive income during 2022. The following benefit payments are expected to be paid in each of the fiscal years as follows: December 31, 2021 (In thousands) 2022 3,594 2023 3,708 2024 3,854 2025 3,956 2026 4,043 2027 through 2030 20,543 Total $ 39,698

Purchase Commitments

Purchase Commitments	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Purchase Commitments	Purchase Commitments As of December 31, 2021, the Company had outstanding commitments to acquire revenue equipment of $858.0 million in 2022 ($585.8 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 operating leases, finance leases, debt, proceeds from sales of existing equipment, and cash flows from operations. As of December 31, 2021, the Company had outstanding purchase commitments to acquire facilities and non-revenue equipment of $53.4 million in 2022, $4.5 million in the two-year period 2023 through 2024 , and $1.2 million in the two-year period 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	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Legal Proceedings	Contingencies and Legal Proceedings Accounting Policy The Company is involved in certain claims and pending litigation primarily arising in the normal course of business. The majority of these claims relate to workers' compensation, auto collision and liability, physical damage, and cargo damage, as well as certain class action litigation in which plaintiffs allege failure to provide meal and rest breaks, unpaid wages, unauthorized deductions, and other items. The Company accrues for the uninsured portion of claims losses and the gross amount of other losses when the likelihood of the loss is probable and the amount of the loss is reasonably estimable. These accruals are based on management's best estimate within a possible range of loss. When there is no amount within the range of loss that appears to be a better estimate than any other amount, then management accrues to the low end of the range. Legal fees are expensed as incurred. When it is reasonably possible that exposure exists in excess of the related accrual (which could be no accrual), management discloses an estimate of the possible loss or range of loss, unless an estimate cannot be determined (because, among other reasons, (1) the proceedings are in various stages that do not allow for assessment; (2) damages have not been sought; (3) damages are unsupported and/or exaggerated; (4) there is uncertainty as to the outcome of pending appeals; and/or (5) there are significant factual issues to be resolved). If the likelihood of a loss is remote, the Company does not accrue for the loss. However, if the likelihood of a loss is remote, but it is at least reasonably possible that one or more future confirming events may materially change management's estimate within twelve months from the date of the financial statements, management discloses an estimate of the possible loss or range of loss, unless an estimate cannot be determined. 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 consolidated balance sheets. The Company has recorded an aggregate accrual of approximately $18.1 million and $20.2 million relating to the Company's outstanding legal proceedings as of December 31, 2021 and 2020, respectively. 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 CRST Expedited The plaintiff alleges tortious interference with contract and unjust enrichment related to non-competition agreements entered into with certain of its drivers. Plaintiff(s) Defendant(s) Date instituted Court or agency currently pending in CRST Expedited, Inc. Swift Transportation Co. of Arizona LLC. March 20, 2017 United States District Court for the Northern District of Iowa Recent Developments and Current Status In July 2019, a jury issued an adverse verdict in this lawsuit. The court issued a decision granting in part and denying in part certain motions related to the jury’s verdict. Both parties have appealed the court’s decision. On August 6, 2021 a three-judge panel of the 8th Circuit Court of Appeals issued an opinion reversing the trial court’s decision. On October 4, 2021 the 8th Circuit Court of Appeals denied a petition for rehearing. The likelihood that a loss has been incurred is no longer probable, and the accrual for this lawsuit has accordingly been reversed as of December 31, 2021. 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 December 31, 2021. 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 FLSA 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 Unites 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 December 31, 2021, the Company has accrued for anticipated costs associated with finalizing this matter. 1 Individually and on behalf of all others similarly situated. Other Environmental The Company's tractors and trailers are involved in motor vehicle accidents, experience damage, mechanical failures and cargo issues as an incidental part of the normal ordinary course of operations. From time to time, these matters result in the discharge of diesel fuel, motor oil, or other hazardous materials into the environment. Depending on local regulations and who is determined to be at fault, the Company is sometimes responsible for the clean-up costs associated with these discharges. As of December 31, 2021, the Company's estimate for its total legal liability for all such clean-up and remediation costs was approximately $1.1 million in the aggregate for all current and prior year claims.

Share Repurchase Plans

Share Repurchase Plans	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Share Repurchase Plans	Share Repurchase Plans On May 31, 2019, the Company announced that the Board approved the repurchase of up to $250.0 million worth of the Company's outstanding common stock (the "2019 Knight-Swift Share Repurchase Plan"). With the adoption of the 2019 Knight-Swift Share Repurchase Plan, the Company terminated the previous share repurchase plan. There was approximately $0.2 million of authorized purchases remaining under the previous share repurchase plan upon termination. 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"). With the adoption of the 2020 Knight-Swift Share Repurchase Plan, the Company terminated the 2019 Knight-Swift Share Repurchase Plan. There was approximately $54.1 million of authorized purchases remaining under the 2019 Knight-Swift Share Repurchase Plan upon termination. The following table presents the Company's repurchases of its common stock under the respective share repurchase plans, excluding advisory fees: Share Repurchase Plan 2021 2020 Board Approval Date Authorized Amount Shares Amount Shares Amount (in thousands) May 30, 2019 $250,000 — — 4,841 179,585 November 24, 2020 1 $250,000 1,377 57,175 — — 1,377 $ 57,175 4,841 $ 179,585 1 $192.8 million and $250.0 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of December 31, 2021 and December 31, 2020, respectively . Subsequent to December 31, 2021, the Company repurchased 0.7 million shares for $36.9 million under the 2020 Knight-Swift Share Repurchase Plan, leaving $155.9 million available as of February 22, 2022.

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-based compensation	Stock-based Compensation Compensatory Stock Plans Before the 2017 Merger, Knight and Swift granted stock-based awards under their respective stock-based compensation plans, discussed below. 2014 Stock Plan — Currently, the 2014 Stock Plan, as amended and restated, is the Company’s only compensatory stock-based incentive plan. The previous 2014 stock plan replaced Swift's 2007 Omnibus Incentive Plan when it was adopted by Swift's board of directors in March 2014 and then approved by the Swift stockholders in May 2014. The previous 2014 stock plan was amended and restated to rename the plan and for other administrative changes relating to the 2017 Merger. The 2014 Stock Plan was again amended and restated in 2020 to increase the number of shares of common stock available for issuance and extended the term of the 2014 Stock Plan, as well as to amend certain provisions to comply with best practices. Other terms of the 2014 Stock Plan, as amended and restated, remain substantially the same as the previous 2014 stock plan and first amended and restated stock plan. The 2014 Stock Plan, as amended and restated, permits the payment of cash incentive compensation and authorizes the granting of stock options, stock appreciation rights, restricted stock and restricted stock units, performance shares and performance units, cash-based awards, and stock-based awards to the Company's employees and non-employee directors. As of December 31, 2021, the aggregate number of shares remaining available under the 2014 Stock Plan was approximately 4.7 million. Legacy Plans — In connection with the 2017 Merger, the registered securities under the Knight Amended and Restated 2003 Stock Option Plan, the Knight 2012 Equity Compensation Plan, the Knight Amended and Restated 2015 Omnibus Incentive Plan, and the Swift 2007 Omnibus Incentive Plan (collectively, the "Legacy Plans") were deregistered. As such, no future awards may be granted under these Legacy Plans. Outstanding awards granted under the Legacy Plans were assumed by Knight-Swift and continue to be governed by such Legacy Plans until such awards have been exercised, forfeited, canceled, or have otherwise expired or terminated. See Note 2 regarding the Company's accounting policy for stock-based compensation. Stock-based Compensation Expense Stock-based compensation expense, net of forfeitures, which is included in "Salaries, wages, and benefits" in the consolidated statements of comprehensive income is comprised of the following: 2021 2020 2019 (In thousands) Stock options $ 232 $ 567 $ 1,149 Restricted stock units 18,190 13,496 9,734 Performance units 15,073 5,576 2,492 Stock-based compensation expense – equity awards $ 33,495 $ 19,639 $ 13,375 Stock-based compensation (benefit) expense – liability awards 1 (5,364) 6,955 2,663 Total stock-based compensation expense, net of forfeitures $ 28,131 $ 26,594 $ 16,038 Income tax benefit 2 $ 8,357 $ 4,949 $ 3,344 1 Includes awards granted to executive management in November 2019 that, per the original agreement, would ultimately settle in cash upon fulfilling a requisite service period (for restricted stock units) and fulfilling a requisite service period and achieving performance targets (for performance units). During 2021, the Company amended the agreements for outstanding awards to ultimately settle in shares after each requisite service period. 2 The income tax benefit is calculated by applying the statutory tax rate to stock-based compensation expense for equity awards, as the expense associated with liability awards is not tax deductible. Unrecognized Stock-based Compensation Expense The following table presents the total unrecognized stock-based compensation expense and the expected weighted average period over which these expenses will be recognized: December 31, 2021 Expense Weighted Average Period (In thousands) (In years) Equity awards – Restricted stock units 49,704 2.2 Equity awards – Performance units 14,306 2.4 Total unrecognized stock-based compensation expense $ 64,010 2.3 Stock Award Grants 2021 2020 2019 Restricted stock units 562,021 722,499 588,819 Performance units 112,690 146,036 102,776 Equity awards granted 674,711 868,535 691,595 Liability awards granted 1 2 — — 80,927 Total stock awards granted 674,711 868,535 772,522 1 Includes 48,556 performance units in 2019. 2 Includes 32,371 restricted stock units in 2019. Stock Options Stock options are the contingent right of award holders to purchase shares of the Company's common stock at a stated price for a limited time. The exercise price of options granted equals the fair value of the Company's common stock determined by the closing price of the Company's common stock quoted on the NYSE on the grant date. Most stock options granted by the Company cannot be exercised until at least one year after the grant date and have a five to ten-year contractual term. Stock options are generally forfeited upon termination of employment for reasons other than death, disability, or retirement. A summary of 2021 stock option activity follows: Stock options outstanding: Shares Under Option Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value 1 (In years) (In thousands) Stock options outstanding at December 31, 2020 302,976 $ 29.45 1.2 $ 3,748 Granted — — Exercised (207,242) 28.59 Expired (7,419) 23.80 Forfeited (3,308) 33.35 Stock options outstanding at December 31, 2021 85,007 $ 31.95 0.6 $ 2,464 Aggregate number of stock options expected to vest at a future date as of December 31, 2021 — $ — 0.0 $ — Exercisable at December 31, 2021 85,007 $ 31.95 0.6 $ 2,464 1 The aggregate intrinsic value was computed using the closing share price on December 31, 2021 of $60.94 and on December 31, 2020 of $41.82, as applicable. The following table summarizes stock option exercise information for the years presented: Stock option exercises 2021 2020 2019 (In thousands, except share data) Number of stock options exercised 207,242 382,254 443,288 Intrinsic value of stock options exercised $ 4,120 $ 4,929 $ 5,183 Cash received upon exercise of stock options $ 5,924 $ 10,199 $ 10,478 Income tax benefit $ 1,304 $ 1,029 $ 221 The following table is a rollforward of the Company's unvested stock options: Unvested stock options: Shares Weighted Average Fair Value Unvested stock options at December 31, 2020 86,779 $ 6.78 Vested (83,707) 6.78 Forfeited and canceled (3,072) 6.78 Unvested stock options at December 31, 2021 — $ — The total fair value of the shares vested during 2021, 2020, and 2019 was $0.6 million, $1.0 million, and $1.5 million, respectively. Restricted Stock Units A restricted stock unit represents a right to receive a common share of stock when the unit vests. Restricted stock unit recipients do not have voting rights with respect to the shares underlying unvested awards. Employees generally forfeit their units if their employment terminates before the vesting date, with the exception of death, disability or retirement. The following table is a rollforward of unvested restricted stock units, including restricted stock units classified as equity and those classified as liabilities: Unvested restricted stock units: Number of Awards Weighted Average Fair Value 1 Unvested restricted stock units at December 31, 2020 1,723,838 $ 34.07 Granted 562,021 50.63 Vested 2 (456,670) 32.53 Forfeited (119,428) 39.97 Unvested restricted stock units at December 31, 2021 1,709,761 $ 39.81 1 The fair value of each restricted stock unit is based on the closing market price on the grant date. 2 Includes 170,280 shares withheld for taxes and 18,697 net units settled in cash which were excluded from the "Common stock issued to employees" activity within the consolidated statements of stockholders' equity. Performance Units The Company issues performance units to select key employees, that may be earned based on achieving performance targets approved by the compensation committee annually. The initial award is subject to an adjustment determined by the Company's performance achieved over a three-year performance period when compared to the objective performance standards adopted by the compensation committee. Furthermore, the performance units have additional service requirements subsequent to the achievement of the performance targets. Performance units do not earn dividend equivalents. The following table is a rollforward of unvested performance units, including performance units classified as equity and those classified as liabilities: Unvested performance units: Shares Weighted Average Fair Value Unvested performance units at December 31, 2020 549,730 $ 39.50 Granted 112,690 $ 60.55 Shares earned above target 45,409 $ 37.89 Vested 1 (136,225) $ 45.02 Unvested performance units at December 31, 2021 2 571,604 $ 44.22 1 Includes 63,815 shares withheld for taxes and 39,225 net units settled in cash which were excluded from the "Common stock issued to employees" activity within the consolidated statements of stockholders' equity. 2 The performance measurement period for performance units granted in 2018 is January 1, 2019 to December 31, 2021 (three full calendar years). The performance measurement period for performance units granted in 2019 is January 1, 2020 to December 31, 2022 (three full calendar years). The performance measurement period for performance units granted in 2020 is January 1, 2021 to December 31, 2023 (three full calendar years). The performance measurement period for units granted in 2021 is January 1, 2022 to December 31, 2024 (three full calendar years). All performance units will vest one month following the expiration of the performance measurement period. The following table presents the weighted average assumptions used in the fair value computation for performance units, including performance units classified as equity and those classified as liabilities: Performance unit fair value assumptions: 2021 2020 2019 Dividend yield 1 0.67 % 0.78 % 0.66 % Expected volatility 2 36.00 % 37.99 % 34.88 % Average peer volatility 2 35.49 % 35.62 % 27.96 % Average peer correlation coefficient 3 0.60 0.59 0.60 Risk-free interest rate 4 0.92 % 0.20 % 1.60 % Expected term (in years) 5 3.1 3.1 3.1 Weighted-average fair value of performance units granted $ 60.55 $ 42.41 $ 37.24 1 The dividend yield, used to project stock price to the end of the performance period, is based on the Company's historical experience and future expectation of dividend payouts. Total stockholder return is determined assuming that dividends are reinvested in the issuing entity over the performance period, which is mathematically equivalent to utilizing a 0% dividend yield. 2 Management (or peer company) estimated volatility using the Company's (or peer company's) historical share price performance over the remaining performance period as of the grant date. 3 The correlation coefficients are used to model the way in which each entity tends to move in relation to each other; the correlation assumptions were developed using the same stock price data as the volatility assumptions. 4 The risk-free interest rate assumption is based on US Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the performance award. 5 Since the Monte Carlo Simulation valuation is an open form model that uses an expected life commensurate with the performance period, the expected life of the performance units was assumed to be the period from the grant date to the end of the performance period. Non-compensatory Stock Plan: ESPP The Company's 2012 ESPP is administered by the Company, is intended to qualify under Section 423 of the Internal Revenue Code, and is considered noncompensatory. Pursuant to the 2012 ESPP, the Co mpany is authorized to issue up to 1.4 million shares of its common stock to eligible employees who participate in the plan. Employees are eligible to participate in the 2012 ESPP following at least 90 days of employment with the Company or any of its participating subsidiaries. Under the terms of the 2012 ESPP, eligible employees may elect to purchase common stock through payroll deductions, not to exceed 15% of their gross cash compensation. The purchase price of the common stock is 95% of the common stock's fair market value quoted on the NYSE on the last trading day of each offering period. There are four three-month offering periods corresponding to the calendar quarters. Each eligible employee is restricted to purchasing a maximum of $6,250 of common stock during an offering period, determined by the fair market value of the common stock as of the last day of the offering period, and $25,000 of common stock during a calendar year. Officers or employees who own 5% or more of the total voting power or value of common stock are restricted from participating in the 2012 ESPP. The plan was amended effective January 1, 2019 to align with new federal tax legislation that lifted the restriction on contributing to the ESPP if the participant had a hardship withdrawal on the 401(k) plan. In 2021, the Company issued approximately 63,000 shares under the 2012 ESPP at a weighted average discounted price per share of $44.12. As of December 31, 2021, the Company is authorized to issue an additional 1.0 million shares under the 2012 ESPP.

Weighted Average Shares Outstan

Weighted Average Shares Outstanding	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Weighted Average Shares Outstanding	Weighted Average Shares Outstanding Earnings per share, basic and diluted, as presented in the 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: 2021 2020 2019 (In thousands) Basic weighted average common shares outstanding 165,860 169,711 171,541 Dilutive effect of equity awards 1,200 838 601 Diluted weighted average common shares outstanding 167,060 170,549 172,142 Anti-dilutive shares excluded from earnings per diluted share 1 208 63 603 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.

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement ASC 820, Fair Value Measurements and Disclosures, requires that the Company disclose estimated fair values for its financial instruments. The estimated fair value of a financial instrument is the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date in the principal or most advantageous market for the asset or liability. Fair value estimates are made at a specific point in time and are based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company's entire holdings of a particular financial instrument. Changes in assumptions could significantly affect these estimates. Because the fair value is estimated as of December 31, 2021 and 2020, the amounts that will actually be realized or paid at settlement or maturity of the instruments in the future could be significantly different. The estimated fair values of the Company's financial instruments represent management's best estimates of the amounts that would be received to sell those assets or that would be paid to transfer those liabilities in an orderly transaction between market participants at that date. The estimated fair value measurements maximize the use of observable inputs. However, in situations where there is little, if any, market activity for the asset or liability at the measurement date, the estimated fair value measurement reflects management's own judgments about the assumptions that market participants would use in pricing the asset or liability. These judgments are developed by the Company based on the best information available under the circumstances. The following summary presents a description of the methods and assumptions used to estimate the fair value of each class of financial instrument. Restricted Investments, Held-to-Maturity — The estimated fair value of the Company's restricted investments is based on quoted prices in active markets that are readily and regularly obtainable. See Note 5 for additional investments disclosures regarding restricted investments, held-to-maturity. Convertible Notes — The estimated fair value of the Company's convertible note is based on probability weighted discounted cash flow analysis of the corresponding pay-off/redemption. Equity Method Investments — The estimated fair value of the Company's equity method investments are privately negotiated investments. The carrying amount of these investments approximates the fair value. Equity Securities — The estimated fair value of the Company's investments in equity securities is based on quoted prices in active markets that are readily and regularly obtainable. Pension Plan Assets — The estimated fair value of ACT's pension plan assets are based on quoted prices in active markets that are readily and regularly obtainable. Debt Instruments and Leases — For notes payable under the 2021 Revolver, the 2021 Term Loans, the 2021 Prudential Notes, the 2017 Revolver, and the 2017 Term Loan, fair value approximates the carrying value due to the variable interest rate. The carrying values of the 2021 RSA and 2018 RSA approximate fair value, as the underlying receivables are short-term in nature and only eligible receivables (such as those with high credit ratings) are qualified to secure the borrowed amounts. For finance and operating lease liabilities, the carrying value approximates the fair value, as the Company's finance and operating lease liabilities are structured to amortize in a manner similar to the depreciation of the underlying assets. Contingent Consideration — The estimated fair value of the Company's contingent consideration owed to sellers is calculated using applicable models and inputs for each acquired entity. Other — Cash and cash equivalents, restricted cash, net accounts receivable, income tax refund receivable, and accounts payable represent financial instruments for which the carrying amount approximates fair value, as they are short-term in nature. These instruments are accordingly excluded from the disclosures below. All remaining balance sheet amounts excluded from the below are not considered financial instruments, subject to this disclosure. Fair Value Hierarchy — ASC 820 establishes a framework for measuring fair value in accordance with GAAP and expands financial statement disclosure requirements for fair value measurements. ASC 820 further specifies a hierarchy of valuation techniques, which is based on whether the inputs into the valuation technique are observable or unobservable. The hierarchy follows: • Level 1 — Valuation techniques in which all significant inputs are quoted prices from active markets for assets or liabilities that are identical to the assets or liabilities being measured. • Level 2 — Valuation techniques in which significant inputs include quoted prices from active markets for assets or liabilities that are similar to the assets or liabilities being measured and/or quoted prices from markets that are not active for assets or liabilities that are identical or similar to the assets or liabilities being measured. Also, model-derived valuations in which all significant inputs and significant value drivers are observable in active markets are Level 2 valuation techniques. • Level 3 — Valuation techniques in which one or more significant inputs or significant value drivers are unobservable. Unobservable inputs are valuation technique inputs that reflect the Company's own assumptions about the assumptions that market participants would use in pricing an asset or liability. The following table presents the carrying amounts and estimated fair values of the Company's major categories of financial assets and liabilities: December 31, 2021 December 31, 2020 Consolidated Balance Sheets Caption Carrying Estimated Carrying Estimated (In thousands) Financial Assets: Restricted investments, held-to-maturity 1 Restricted investments, held-to-maturity, amortized cost $ 5,866 $ 5,859 $ 9,001 $ 8,995 Equity method investments Other long-term assets 75,769 75,769 77,562 77,562 Investments in equity securities Other long-term assets 74,201 74,201 18,675 18,675 Convertible note Other long-term assets 10,141 10,141 — — Financial Liabilities: 2021 Term Loan A-1, due December 2022 2 Long-term debt – less current portion 199,676 200,000 — — 2021 Term Loan A-2, due September, 2024 2 Long-term debt – less current portion 199,607 200,000 — — 2021 Term Loan A-3, due September 2026 2 Long-term debt – less current portion 798,352 800,000 — — 2021 Revolver, due September 2026 Revolving line of credit 260,000 260,000 — — 2021 Prudential Notes 3 Finance lease liabilities and long-term debt 47,265 47,354 — — 2021 RSA, due April 2024 4 Accounts receivable securitization 278,483 279,000 — — Contingent consideration associated with acquisition Accrued liabilities, Other long-term liabilities 13,100 13,100 16,200 16,200 2017 Term Loan, due October 2022 5 Long-term debt – less current portion $ — $ — $ 298,907 $ 300,000 2017 Revolver, due October 2022 Revolving line of credit — — 210,000 210,000 2018 RSA, due July 2021 6 Accounts receivable securitization — — 213,918 214,000 1 Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity. 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 $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 3 The carrying amount of the 2021 Prudential Notes is net of $0.1 million in deferred loan costs and $2.4 million in fair value adjustments as of December 31, 2021 . 4 The carrying amount of the 2021 RSA is net of $0.5 million in deferred loan costs as of December 31, 2021. 5 The carrying amount of the 2017 Term Loan is net of $1.1 million in deferred loan costs as of December 31, 2020 6 The carrying amount of the 2018 RSA is net of $0.1 million in deferred loan costs as of December 31, 2020. Recurring 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 recurring basis as of December 31, 2021 and 2020: Fair Value Measurements at Reporting Date Using Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Unrealized Gain Position (In thousands) As of December 31, 2021 Convertible note 1 $ 10,141 $ — $ — $ 10,141 $ 141 Investments in equity securities 2 74,201 74,201 — — 14,456 As of December 31, 2020 Investments in equity securities 3 18,675 18,675 — — 3,553 1 The Company recognized $0.1 million of unrealized gains on the convertible note during 2021, which is included within "Other income, net" within the consolidated statements of comprehensive income. 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 income, net" within the consolidated statements of comprehensive income. During 2021, the Company recognized $16.4 million in gains on these investments in equity securities, consisting of $10.9 million in unrealized gains and $5.5 million in realized gains. 3 Fair value activity from the investments in equity securities is recorded in "Other income, net" within the consolidated statements of comprehensive income. During 2020, the Company recognized $3.7 million in unrealized gains on these investments in equity securities. 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 December 31, 2021 and 2020. Fair Value Measurements at Reporting Date Using Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Gain (Loss) (In thousands) As of December 31, 2021 Contingent consideration associated with acquisition 1 $ 13,100 $ — $ — $ 13,100 $ — As of December 31, 2020 Contingent consideration associated with acquisition 2 16,200 — — 16,200 (6,730) 1 The Company did not recognize any gains (losses) during 2021 related to the revaluation of these liabilities. Refer to Note 4 for information regarding the components of these liabilities. 2 During the fourth quarter of 2020, the Company increased the estimated fair value of the remaining contingent consideration representing the final two annual payments, resulting in a $6.7 million fair value adjustment of the deferred earnout, which was recorded in “Miscellaneous operating expenses” in the consolidated statement of comprehensive income. Nonrecurring 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 nonrecurring basis as of December 31, 2021 and 2020: Fair Value Measurements at Reporting Date Using Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Loss (In thousands) As of December 31, 2021 Equipment 1 $ — $ — $ — $ — $ (299) As of December 31, 2020 Equipment 2 5,851 — 5,851 — (5,335) 1 Reflects the non-cash impairment of certain revenue equipment held for sale (within the non-reportable segments and the Truckload segment). 2 Reflects the non-cash impairment of certain alternative fuel technology (within the non-reportable segments) and certain revenue equipment held for sale (within the Truckload segment). The Company recognized $5.3 million of impairments during 2020. Nonrecurring Fair Value Measurements (Liabilities) — As of December 31, 2021 and 2020 there were no liabilities included in the Company's consolidated balance sheets at estimated fair value that were measured on a nonrecurring basis. Fair Value of Pension Plan Assets — The following table sets forth the level within 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 these 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 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	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The following table presents Knight-Swift's transactions with companies controlled by and/or affiliated with its related parties: 2021 2020 2019 Provided by Knight-Swift Received by Knight-Swift Provided by Knight-Swift Received by Knight-Swift Provided by Knight-Swift Received by Knight-Swift (In thousands) Freight Services: Central Freight Lines 1 $ — $ — $ 7,837 $ — $ 19,651 $ — SME Industries 1 — — 56 — 345 — Total $ — $ — $ 7,893 $ — $ 19,996 $ — Facility and Equipment Leases: Central Freight Lines 1 $ — $ — $ 48 $ 277 $ 322 $ 369 Other Affiliates 1 — 311 11 229 18 — Total $ — $ 311 $ 59 $ 506 $ 340 $ 369 Other Services: Central Freight Lines 1 $ — $ — $ 427 $ — $ 1,834 $ — DPF Mobile 1 — — — 33 — 220 Other Affiliates 1 31 35 15 35 39 2,432 Total $ 31 $ 35 $ 442 $ 68 $ 1,873 $ 2,652 1 Entities affiliated with former Board member Jerry Moyes include Central Freight Lines, SME Industries, and DPF Mobile. "Other 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. • Freight Services Provided by Knight-Swift — The Company charges each of these companies for transportation services. • Freight Services Received by Knight-Swift — Transportation services received from Central Freight represent less-than-truckload freight services rendered to haul parts and equipment to Company shop locations. • Other Services Provided by Knight-Swift — Other services provided by the Company to the identified related parties include equipment sales and miscellaneous services. • Other Services Received by Knight-Swift — Consulting fees, diesel particulate filter cleaning, sales of various parts and tractor accessories, and certain third-party payroll and employee benefits administration services from the identified related parties are included in other services received by the Company. During the quarter ended September 30, 2020, the ownership percentage of Jerry Moyes and related affiliates fell below the threshold requiring related party disclosure. The amounts included in this Note 24 pertain to transactions that occurred prior to the date that the ownership percentage changed. Receivables and payables pertaining to related party transactions were: December 31, 2021 2020 Receivable Payable Receivable Payable (In thousands) Central Freight Lines $ — $ — $ 133 $ — DPF Mobile — — — 41 Other Affiliates 14 44 2 10 Total $ 14 $ 44 $ 135 $ 51

Information by Segment, Geograp

Information by Segment, Geography, and Customer Concentration	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Information by Segment, Geography, and Customer Concentration	Information by Segment, Geography, and Customer Concentration Segment Information The Company has four reportable segments: Truckload, Logistics, LTL, and Intermodal, as well as the non-reportable segments, discussed below. Based on how economic factors affect the nature, amount, timing, and uncertainty of revenue or cash flows, the Company disaggregates revenues by reportable segment for the purposes of applying the ASC 606 guidance. The Company's twenty-four operating segments are structured around the types of transportation service offerings provided to our customers, as well as the equipment utilized. In addition, the operating segments may be further distinguished by the Company’s respective brands. The Company aggregated these various operating segments into the four reportable segments discussed below based on similarities with both their qualitative and economic characteristics. Truckload The Truckload reportable segment is comprised of nine full truckload operating segments that provide similar transportation services to the Company's customers utilizing similar transportation equipment over both irregular (one-way movement) and/or dedicated routes. The Truckload reportable segment consists of irregular route and dedicated, refrigerated, expedited, flatbed, and cross-border operations. Logistics The Logistics reportable segment is comprised of six logistics operating segments that provide similar transportation services to the Company's customers and primarily consist of brokerage and other freight management services utilizing third-party transportation providers and their equipment. LTL Our LTL segment, established in 2021 through the ACT and MME acquisitions, is comprised of two operating segments and provides our customers with regional LTL transportation services through a network of approximately 100 service centers in the Company's geographical footprint. The Company's LTL service also includes national coverage to customers by utilizing partner carriers for areas outside of the Company's direct network. Intermodal The Intermodal reportable segment is comprised of two intermodal operating segments that provide similar transportation services to the Company's customers. These transportation services include arranging the movement of customers' freight through third-party intermodal rail services on the Company’s trailing equipment (containers and trailers on flat cars), as well as drayage services to transport loads between the railheads and customer locations. Non-reportable The non-reportable segments include five operating segments that consist of support services provided to the Company's customers and independent contractors (including repair and maintenance shop services, equipment leasing, warranty services, and insurance), trailer parts manufacturing, warehousing, and certain driving academy activities, as well as certain corporate expenses (such as legal settlements and accruals, certain impairments, and amortization of intangibles related to the 2017 Merger and various acquisitions). Intersegment Eliminations Certain operating segments provide transportation and related services for other affiliates outside their segments. For certain operating segments, such services are billed at cost, and no profit is earned. For the other operating segments, revenues for such services are based on negotiated rates, and are reflected as revenues of the billing segment. These rates are adjusted from time to time, based on market conditions. Such intersegment revenues and expenses are eliminated in Knight-Swift's consolidated results. The following tables present the Company's financial information by segment: 2021 2020 2019 Total revenue: (Dollars in thousands) Truckload $ 4,098,005 68.3 % $ 3,786,030 81.0 % $ 3,952,866 81.6 % Logistics $ 817,003 13.6 % $ 375,841 8.0 % $ 352,988 7.3 % LTL $ 396,308 6.6 % $ — — % $ — — % Intermodal $ 458,867 7.7 % $ 391,462 8.4 % $ 455,466 9.4 % Subtotal $ 5,770,183 96.2 % $ 4,553,333 97.4 % $ 4,761,320 98.3 % Non-reportable segments $ 306,414 5.1 % $ 188,882 4.0 % $ 130,782 2.7 % Intersegment eliminations $ (78,578) (1.3 %) $ (68,352) (1.4 %) $ (48,152) (1.0 %) Total revenue $ 5,998,019 100.0 % $ 4,673,863 100.0 % $ 4,843,950 100.0 % 2021 2020 2019 Operating income (loss): (Dollars in thousands) Truckload $ 784,436 81.2 % $ 578,512 102.5 % $ 468,749 109.7 % Logistics $ 93,920 9.7 % $ 20,245 3.6 % $ 21,869 5.1 % LTL $ 31,169 3.2 % $ — — % $ — — % Intermodal $ 42,060 4.4 % $ (943) (0.2 %) $ 4,501 1.1 % Subtotal $ 951,585 98.5 % $ 597,814 105.9 % $ 495,119 115.9 % Non-reportable segments $ 14,112 1.5 % $ (33,376) (5.9 %) $ (67,681) (15.9 %) Operating income $ 965,697 100.0 % $ 564,438 100.0 % $ 427,438 100.0 % 2021 2020 2019 Depreciation and amortization of property and equipment: (Dollars in thousands) Truckload $ 422,558 80.9 % $ 390,417 84.7 % $ 355,270 84.6 % Logistics $ 1,357 0.3 % $ 829 0.2 % $ 728 0.2 % LTL $ 24,844 4.8 % $ — — % $ — — % Intermodal $ 15,345 2.9 % $ 14,377 3.1 % $ 13,506 3.2 % Subtotal $ 464,104 88.9 % $ 405,623 88.0 % $ 369,504 88.0 % Non-reportable segments $ 58,492 11.1 % $ 55,152 12.0 % $ 50,578 12.0 % Consolidated depreciation and amortization of property and equipment $ 522,596 100.0 % $ 460,775 100.0 % $ 420,082 100.0 % Geographical Information In aggregate, operating revenue from the Company's foreign operations was less than 5.0% of consolidated total revenue for each of 2021, 2020, and 2019. Additionally, long-lived assets on the balance sheets of the Company's foreign subsidiaries were less than 5.0% of consolidated "Total assets" as of December 31, 2021 and 2020. Customer Concentration Services provided to the Company's largest customer generated 16.1%, 16.8%, and 13.3% of total revenue in 2021, 2020, and 2019, respectively. Revenue generated by the Company's largest customer is reported in each of our reportable operating segments. No other customer accounted for 10.0% or more of total revenue in 2021, 2020 , or 2019 .

Introduction and Basis of Pre_2

Introduction and Basis of Presentation (Policies)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting, Policy [Policy Text Block]	In management's opinion, these consolidated financial statements were prepared in accordance with GAAP and include all adjustments necessary (consisting of normal recurring adjustments) for the fair presentation of the periods presented.
Consolidation, Policy [Policy Text Block]	With respect to transactional/durational data, references to "years", including "2021", "2020", and "2019" pertain to calendar years. Similarly, references to "quarters", including "first", "second", "third", and "fourth" pertain to calendar quarters.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Use of Estimates, Policy [Policy Text Block]	Use of Estimates — The preparation of the consolidated financial statements, in accordance with GAAP, requires management to make estimates and assumptions about future events that affect the amounts reported in the Company's consolidated financial statements and accompanying notes. On an ongoing basis, management evaluates and periodically adjusts its estimates and assumptions, based on historical experience, the impact of the current economic environment, and other key factors. Volatile energy markets, as well as changes in consumer spending have increased the inherent uncertainty in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Significant items subject to such estimates and assumptions include: • carrying amount of property and equipment; • carrying amount of goodwill and intangible assets; • leases; • estimates of claims accruals; • contingent obligations; • calculation of stock-based compensation; • valuation allowance for deferred income tax assets; • valuation allowances for receivables; and • valuation of financial instruments.
Segments, Policy [Policy Text Block]	Segments — The Company uses the "management approach" to determine its reportable segments, as well as to determine the basis of reporting the operating segment information. Certain of the Company's operating segments have been aggregated into reportable segments. The management approach focuses on financial information that management uses to make operating decisions. The Company's chief operating decision makers use total revenue, operating expense categories, operating ratios, operating income, and key operating statistics to evaluate performance and allocate resources to the Company's operations and is based around the transportation service offerings provided to the Company's customers, as well as the equipment utilized. Operating income is the measure that management uses to evaluate segment performance and allocate resources. Operating income should not be viewed as a substitute for GAAP net income. Management believes the presentation of operating income enhances the understanding of the Company's performance by highlighting the results of operations and the underlying profitability drivers of the business segments. Operating income is defined as "Total revenue" less "Total operating expenses." Based on the unique nature of the Company's operating structure, certain revenue-generating assets are interchangeable between segments. Additionally, the Company's chief operating decision makers do not review assets or liabilities by segment to make operating decisions. The Company allocates depreciation and amortization expense of its property and equipment to the segments based on the actual utilization of the asset by the segment during the period.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents — Cash and cash equivalents are comprised of cash, money market funds, and highly liquid instruments with insignificant interest rate risk and original maturities of three months or less. Cash balances with institutions may be in excess of Federal Deposit Insurance Corporation ("FDIC") limits or may be invested in sweep accounts that are not insured by the institution, the FDIC, or any other government agency. Restricted Cash and Equivalents — The Company's wholly-owned captive insurance companies, Red Rock and Mohave, maintain certain operating bank accounts, working trust accounts, and investment accounts. The cash and cash equivalents within these accounts are restricted by insurance regulations to fund the insurance claim losses to be paid by the captive insurance companies, and therefore, are classified as "Cash and cash equivalents – restricted" and within "Other long-term assets" in the consolidated balance sheets.
Restricted Investments, Policy [Policy Text Block]	Restricted Investments — The Company's investments are restricted by insurance regulations to fund the insurance claim losses to be paid by the captive insurance companies. The Company accounts for its investments in accordance with ASC 320, Investments – Debt Securities . Management determines the appropriate classification of its investments in debt securities at the time of purchase and re-evaluates the determination on a quarterly basis. As of December 31, 2021, all of the Company's investments in fixed-maturity securities were classified as held-to-maturity, as the Company has the positive intent and ability to hold these securities to maturity. Held-to-maturity securities are carried at amortized cost. The amortized cost of debt securities is adjusted using the effective interest rate method for amortization of premiums and accretion of discounts. Amortization and accretion are reported in "Other income, net" in the consolidated statements of comprehensive income.
Inventories and Supplies, Policy [Policy Text Block]	Inventories and Supplies — Inventories and supplies, which are included in "Other current assets" in the consolidated balance sheets, primarily consist of spare parts, tires, fuel, and supplies and are stated at lower of cost or net realizable value. Depending on the class of inventory, cost is determined using the first-in, first-out method or average cost. Replacement tires held in the shops are classified as inventory and expensed when placed in service. Replacement tire costs incurred over the road are immediately expensed.
Property and Equipment, Policy [Policy Text Block]	Property and Equipment — Property and equipment is stated at cost less accumulated depreciation. Costs to construct significant assets include capitalized interest incurred during the construction and development period. Expenditures for replacements and improvements are capitalized. Maintenance and repairs are expensed as incurred. Net gains on the disposal of property and equipment are presented in the consolidated statements of comprehensive income within "Miscellaneous operating expenses." Tires on purchased revenue equipment are capitalized along with the related equipment cost when the vehicle is placed in service, and are depreciated over the life of the vehicle. Depreciation of property and equipment is calculated on a straight-line basis down to the salvage value, as applicable, over the following estimated useful lives: Category: Range (in years) Revenue equipment * 3 — 20 Shop and service equipment 2 — 10 Land improvements 5 — 15 Buildings and building improvements 10 — 40 Furniture and fixtures 3 — 10 Leasehold improvements Life of the lease *For finance leases involving revenue equipment, the depreciation period is equal to the term of the lease agreement. Management believes that these methods properly spread the costs over the useful lives of the assets. Management judgment is involved when determining estimated useful lives of the Company's long-lived assets. Useful lives of the Company's long-lived assets are determined based on historical experience, as well as future expectations regarding the period the Company expects to benefit from the asset. Factors affecting estimated useful lives of property and equipment may include estimating loss, damage, obsolescence, and Company policies around maintenance and asset replacement. Management evaluates its property and equipment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable in accordance with ASC 360, Property, Plant and Equipment . When such events or changes in circumstances occur, management performs a recoverability test that compares the carrying amount with the projected undiscounted cash flows from the use and eventual disposition of the asset or asset group. An impairment is recorded for any excess of the carrying amount over the estimated fair value. Fair value is determined through various valuation techniques including discounted cash flow models, quoted market values, and third-party independent appraisals, when necessary. Estimating fair value includes several significant assumptions, including future cash flow estimates, determination of appropriate discount rates, and other assumptions that management believes reasonable under the circumstances. Changes in these estimates and assumptions could materially affect the determination of fair value and/or impairment.
Goodwill, Policy [Policy Text Block]	Management evaluates goodwill on an annual basis as of June 30 th , or more frequently if indicators of impairment exist. The Company performs a quantitative analysis on an annual basis, in accordance with ASC 350, Goodwill and Other Intangible Assets . Management estimates the fair values of its reporting units using a combination of the income and market approaches. If the carrying amount of a reporting unit exceeds the fair value, then management recognizes an impairment loss of the same amount. This loss is only limited to the total amount of goodwill allocated to that reporting unit. Refer to Note 10 for the results of the Company's annual evaluation as of June 30, 2021.
Intangible Assets other than Goodwill, Policy [Policy Text Block]	Intangible Assets other than Goodwill — The Company's intangible assets other than goodwill primarily consist of acquired customer relationships, trade names, and other intangibles from acquisitions. Amortization of acquired customer relationships, and other intangibles is calculated on a straight-line basis over the estimated useful life, which ranges from 3 years to 20 years. Certain trade names have indefinite useful lives and are not amortized, but are tested for impairment at least annually, unless events occur or circumstances change between annual tests that would more likely than not reduce the fair value. Management reviews its intangible assets for impairment whenever events or circumstances indicate that the carrying amount of the asset may not be recoverable, in accordance with ASC 350, Intangibles – Goodwill and Other. When such events or changes in circumstances occur, management performs a recoverability test that compares the carrying amount with the projected discounted cash flows from the use and eventual disposition of the asset or asset group. An impairment is recorded for any excess of the carrying amount over the estimated fair value, which is generally determined using discounted future cash flows. Fair value is determined through various valuation techniques, including discounted cash flow models, quoted market values, and third-party independent appraisals. Estimating fair value includes several significant assumptions, including future cash flow estimates, determination of appropriate discount rates, royalty rates, and other assumptions that management believes reasonable under the circumstances. Changes in these estimates and assumptions could materially affect the determination of fair value and/or impairment.
Claims Accruals, Policy [Policy Text Block]	Claims Accruals — The Company is self-insured for a portion of its risk related to auto liability, workers' compensation, property damage, cargo damage, and group health. Self-insurance results from buying insurance coverage that applies in excess of a retained portion of risk for each respective line of coverage. The Company accrues for the cost of the uninsured portion of pending claims by evaluating the nature and severity of individual claims and by estimating future claims development based upon historical claims development trends. The actual cost to settle self-insured claim liabilities may differ from the Company's reserve estimates due to legal costs, claims that have been incurred but not reported, and various other uncertainties, including the inherent difficulty in estimating the severity of the claims and the potential judgment or settlement amount to dispose of the claim.
Leases, Policy [Policy Text Block]	Leases — Management evaluates the Company’s leases based on the underlying asset groups. The assets currently underlying the Company’s leases include revenue equipment (primarily tractors and trailers), real estate (primarily buildings, office space, land, and drop yards), as well as technology and other equipment that supports business operations. Management’s significant assumptions and judgments include the determination of the discount rate (discussed below), as well as the determination of whether a contract contains a lease. In accordance with ASC 842, Leases , property and equipment held under operating leases are recorded as right-of-use assets, with a corresponding operating lease liability. Additionally, property and equipment held under finance leases are recorded as property and equipment with corresponding finance lease liabilities. All expenses related to operating leases are reflected in our consolidated statements of comprehensive income in "Rental expense." Expenses related to finance leases are reflected in our consolidated statements of comprehensive income in "Depreciation and amortization of property and equipment" and "Interest expense." • Lease Term — The Company’s leases generally have lease terms corresponding to the useful lives of the underlying assets. Revenue equipment leases have fixed payment terms based on the passage of time, which is typically three to five years for tractors and five to seven years for trailers. Certain finance leases for revenue equipment contain renewal or fixed price purchase options. Real estate leases, excluding drop yards, generally have varying lease terms between five and fifteen years and may include renewal options. Drop yards include month-to-month leases, as well as leases with varying lease terms generally ranging from two to five years. Options to renew or purchase the underlying assets are considered in the determination of the right-of-use asset and corresponding lease liability once reasonably certain of exercise. • Portfolio Approach — The Company typically leases its revenue equipment under master lease agreements, which contain general terms, conditions, definitions, representations, warranties, and other general language, while the specific contract provisions are contained within the various individual lease schedules that fall under a master lease agreement. Each individual leased asset within a lease schedule is similar in nature (i.e. all tractors or all trailers) and has identical contract provisions to all of the other individual leased assets within the same lease schedule (such as the contract provisions discussed above). Management has elected to apply the portfolio approach to its revenue equipment leases, as accounting for its revenue equipment under the portfolio approach would not be materially different from separately accounting for each individual underlying asset as a lease. Each individual real estate and other lease is accounted for at the individual asset level. • Nonlease Components — Management has elected to combine its nonlease components (such as fixed charges for common area maintenance, real estate taxes, utilities, and insurance) with lease components for each class of underlying asset, as applicable, as the nonlease components in the Company’s lease contracts typically are not material. These nonlease components are usually present within the Company’s real estate leases. The Company’s assets are generally insured by umbrella policies, in which the premiums change from one policy period to the next, making them variable in nature. Accordingly, these insurance costs are excluded from the Company’s calculation of right-of-use assets and corresponding lease liabilities. • Short-Term Lease Exemption — Management has elected to apply the short-term lease exemption to all asset groups. Accordingly, leases with terms of twelve months or less are not capitalized and continue to be expensed on a straight-line basis over the term of the lease. This primarily affects the Company’s drop yards and corresponding temporary structures on those drop yards. To a lesser extent, certain short-term leases for revenue equipment, technology, and other assets are affected. • Discount Rate — The Company uses the rate implicit in the lease, when readily determinable, which is generally related to the Company's finance leases. Otherwise the Company’s incremental borrowing rate is applied. The implicit interest rate is not readily determinable for the Company’s operating leases. As such, management applies the Company’s incremental borrowing rate, which is defined by GAAP as the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. The Company's incremental borrowing rate is based on the results of an independent third-party valuation. • Residual Values — The Company's finance leases for revenue equipment are typically structured with balloon payments at the end of the lease term equal to the residual value the Company is contracted to receive from certain equipment manufacturers upon sale or trade back to the manufacturers. If the Company does not receive proceeds of the contracted residual value from the manufacturer, the Company is still obligated to make the balloon payment at the end of the lease term. In connection with certain revenue equipment operating leases, the Company issues residual value guarantees, which provide that if the Company does not purchase the leased equipment from the lessor at the end of the lease term, then the Company is liable to the lessor for an amount equal to the shortage (if any) between the proceeds from the sale of the equipment and an agreed value. To the extent management believes any manufacturer will refuse or be unable to meet its obligation, the Company recognizes additional rental expense to the extent the fair market value at the lease termination is expected to be less than the obligation to the lessor. Proceeds from the sale of equipment under the Company’s operating leases generally exceed the payment obligation on substantially all operating leases. Although the Company typically owes certain amounts to its lessors at the end of its revenue equipment leases, the Company’s equipment manufacturers have corresponding guarantees back to the Company as to the buyback value of the units.
Revenue [Policy Text Block]	Revenue Recognition — Management applies the five-step analysis to the Company's four reportable segments (Truckload, Logistics, LTL, and Intermodal). • Step 1: Contract Identification — Management has identified that a legally enforceable contract with its customers is executed by both parties at the point of pickup at the shipper's location, as evidenced by the bill of lading. Although the Company may have master agreements with its customers, these master agreements only establish general terms. There is no financial obligation to the shipper until the load is tendered/accepted and the Company takes possession of the load. • Step 2: Performance Obligations — The Company's only performance obligation is transportation services. The Company's delivery, accessorial, and dedicated operations truck capacity in its dedicated operations represent a bundle of services that are highly interdependent and have the same pattern of transfer to the customer. These services are not capable of being distinct from one another. For example, the Company generally would not provide accessorial services or truck capacity without providing delivery services. • Step 3: Transaction Price — Depending on the contract, the total transaction price may consist of mileage revenue, fuel surcharge revenue, accessorial fees, truck capacity, and/or non-cash consideration. Non-cash consideration is measured by the estimated fair value of the non-cash consideration at contract inception. There is no significant financing component in the transaction price, as the Company's customers generally pay within the contractual payment terms of 30 to 60 days. • Step 4: Allocating Transaction Price to Performance Obligations — The transaction price is entirely allocated to the only performance obligation: transportation services. • Step 5: Revenue Recognition — The performance obligation of providing transportation services is satisfied over time. Accordingly, revenue is recognized over time. Management estimates the amount of revenue in transit at period end based on the number of days completed of the dispatch (which is generally one to three days for the Truckload, Logistics and LTL segments, but can be longer for intermodal operations). Management believes this to be a faithful depiction of the transfer of services because if a load is dispatched, but terminates mid-route and the load is picked up by another carrier, then that carrier would not need to re-perform the services for the days already traveled. The Company outsources the transportation of loads to third-party carriers through its logistics operations. Management has determined that the Company is a principal in these arrangements, and therefore records revenue associated with these contracts on a gross basis. The Company has the primary responsibility to meet the customers' requirements. The Company invoices and collects from its customers and maintains discretion over pricing. Additionally, the Company is responsible for the selection of third-party transportation providers to the extent used to satisfy customer freight requirements. Significant judgments involved in the Company's revenue recognition and corresponding accounts receivable balances include: • Measuring in-transit revenue at period end (discussed above). • Estimating the allowance for doubtful accounts. The Company establishes an allowance for doubtful accounts based on historical experience and any known trends or uncertainties related to customer billing and account collectability. Management reviews the adequacy of its allowance for doubtful accounts on a quarterly basis. Uncollectible accounts are written off when deemed uncollectible, and accounts receivable are presented net of an allowance for doubtful accounts. • Contract Balances — In-transit revenue balances are included in "Contract balance – revenue in transit" in the consolidated balance sheets. The Company's contract liability balances are typically immaterial. • Revenue Disaggregation — In considering the level at which the Company should disaggregate revenues pertaining to contracts with customers, management determined that there are no significant differences between segments in how the nature, amount, timing, and uncertainty of revenue or cash flows are affected by economic factors. Additionally, management considered how and where the Company has communicated information about revenue for various purposes, including disclosures outside of the financial statements and how information is regularly reviewed by the Company's chief operating decision makers for evaluating financial performance of the Company's segments, among others. Based on these considerations, management determined that revenues should be disaggregated by reportable segment. The Company recognizes operating lease revenue from leasing tractors and related equipment to third parties, including independent contractors. Operating lease revenue from rental operations is recognized as earned, which is straight-lined per the rent schedules in the lease agreements. Losses from lease defaults are recognized as offsets to revenue.
Stock-based Compensation, Policy [Policy Text Block]	Stock-based Compensation — The Company accounts for stock-based compensation expense in accordance with ASC 718, Compensation – Stock Compensation. ASC 718 requires that all share-based payments to employees and non-employee directors, including grants of employee stock options, be recognized in the financial statements based upon a grant-date fair value of an award. Equity awards settled in cash are remeasured at each reporting period and are recognized as a liability in the consolidated balance sheets during the vesting period until settlement. • Fair Value — The fair value of performance units is estimated using the Monte Carlo Simulation valuation model. The fair value of stock options is estimated using the Black-Scholes option-valuation model. The fair value of restricted stock units is the closing stock price on the grant date. • Vesting — The requisite service period is the specified vesting date in the grant agreement or the date that the employee becomes retirement-eligible, based on the terms of the grant agreement. The Company calculates the number of awards expected to vest as awards granted, less expected forfeitures over the life of the award (estimated at grant date). All awards require future service and thus forfeitures are estimated based on historical forfeitures and the remaining term until the related award vests. Performance-based awards vest contingent upon meeting certain performance criteria established by the Company's compensation committee. • Expense — Awards that are only subject to time-vesting provisions are amortized using the straight-line method, by amortizing the grant-date fair value over the requisite service period of the entire award. Awards subject to time-based vesting and performance conditions are amortized using the individual vesting tranches. Unless a material deviation from the assumed forfeiture rate is observed during the term in which the awards are expensed, any adjustment necessary to reflect differences in actual experience is recognized in the period the award becomes payable or exercisable.
Income Taxes, Policy [Policy Text Block]	Income Taxes — Management accounts for income taxes under the asset and liability method. Accordingly, deferred tax assets and liabilities are recognized for the future tax consequences of events that have been included in the consolidated financial statements. Additionally, deferred tax assets and liabilities are determined based on the differences between the financial statement carrying amounts and respective tax bases of assets and liabilities (using enacted tax rates in effect for the year in which the differences are expected to reverse). The effect on deferred tax assets and liabilities of changes in tax rates is recognized in income in the period that includes the enactment date. Net deferred incomes taxes are classified as noncurrent in the consolidated balance sheets. A valuation allowance is provided against deferred tax assets if the Company determines it is more likely than not that such assets will not ultimately be realized. In making such determinations, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies, and recent financial operations. To the extent management believes the likelihood of recovery is not sufficient, a valuation allowance is established for the amount determined not to be realizable. Management judgment is necessary in determining the frequency at which the need for a valuation allowance is assessed, the accounting period in which to establish the valuation allowance, as well as the amount of the valuation allowance. Unrecognized tax benefits are defined as the difference between a tax position taken or expected to be taken in a tax return and the benefit recognized and measured pursuant to ASC 740, Income Taxes . The Company does not recognize a tax benefit for uncertain tax positions unless it concludes that it is more likely than not that the benefit will be sustained on audit (including resolutions of any related appeals or litigation processes) by the taxing authority, based solely on the technical merits of the associated tax position. If the recognition threshold is met, the Company recognizes a tax benefit measured at the largest amount of the tax benefit that, in management's judgment, is greater than 50% likely to be realized. The Company records expected incurred interest and penalties related to unrecognized tax positions in "Income tax expense" in the consolidated statements of comprehensive income. To the extent interest and penalties are not assessed with respect to uncertain tax positions, amounts accrued will be reduced and reflected as a reduction of the overall income tax provision. Significant management judgment is required in determining the provision for income taxes and in determining whether deferred tax assets will be realized in full or in part. Management periodically assesses the likelihood that all or some portion of deferred tax assets will be recovered from future taxable income. Management judgment is also required regarding a variety of other factors including the appropriateness of tax strategies. The Company utilizes certain income tax planning strategies to reduce its overall income taxes. It is possible that certain strategies might be disallowed, resulting in an increased liability for income taxes. Significant management judgments are involved in assessing the likelihood of sustaining the strategies and determining the likely range of defense and settlement costs, in the event that tax strategies are challenged by taxing authorities. An ultimate result worse than the Company's expectations could adversely affect its results of operations.

Contingencies and Legal Proce_2

Contingencies and Legal Proceedings (Policies)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Contingencies [Policy Text Block]	The Company is involved in certain claims and pending litigation primarily arising in the normal course of business. The majority of these claims relate to workers' compensation, auto collision and liability, physical damage, and cargo damage, as well as certain class action litigation in which plaintiffs allege failure to provide meal and rest breaks, unpaid wages, unauthorized deductions, and other items. The Company accrues for the uninsured portion of claims losses and the gross amount of other losses when the likelihood of the loss is probable and the amount of the loss is reasonably estimable. These accruals are based on management's best estimate within a possible range of loss. When there is no amount within the range of loss that appears to be a better estimate than any other amount, then management accrues to the low end of the range. Legal fees are expensed as incurred. When it is reasonably possible that exposure exists in excess of the related accrual (which could be no accrual), management discloses an estimate of the possible loss or range of loss, unless an estimate cannot be determined (because, among other reasons, (1) the proceedings are in various stages that do not allow for assessment; (2) damages have not been sought; (3) damages are unsupported and/or exaggerated; (4) there is uncertainty as to the outcome of pending appeals; and/or (5) there are significant factual issues to be resolved). If the likelihood of a loss is remote, the Company does not accrue for the loss. However, if the likelihood of a loss is remote, but it is at least reasonably possible that one or more future confirming events may materially change management's estimate within twelve months from the date of the financial statements, management discloses an estimate of the possible loss or range of loss, unless an estimate cannot be determined.

Fair Value Measurement (Policie

Fair Value Measurement (Policies)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement, Policy [Policy Text Block]	The following summary presents a description of the methods and assumptions used to estimate the fair value of each class of financial instrument. Restricted Investments, Held-to-Maturity — The estimated fair value of the Company's restricted investments is based on quoted prices in active markets that are readily and regularly obtainable. See Note 5 for additional investments disclosures regarding restricted investments, held-to-maturity. Convertible Notes — The estimated fair value of the Company's convertible note is based on probability weighted discounted cash flow analysis of the corresponding pay-off/redemption. Equity Method Investments — The estimated fair value of the Company's equity method investments are privately negotiated investments. The carrying amount of these investments approximates the fair value. Equity Securities — The estimated fair value of the Company's investments in equity securities is based on quoted prices in active markets that are readily and regularly obtainable. Pension Plan Assets — The estimated fair value of ACT's pension plan assets are based on quoted prices in active markets that are readily and regularly obtainable. Debt Instruments and Leases — For notes payable under the 2021 Revolver, the 2021 Term Loans, the 2021 Prudential Notes, the 2017 Revolver, and the 2017 Term Loan, fair value approximates the carrying value due to the variable interest rate. The carrying values of the 2021 RSA and 2018 RSA approximate fair value, as the underlying receivables are short-term in nature and only eligible receivables (such as those with high credit ratings) are qualified to secure the borrowed amounts. For finance and operating lease liabilities, the carrying value approximates the fair value, as the Company's finance and operating lease liabilities are structured to amortize in a manner similar to the depreciation of the underlying assets. Contingent Consideration — The estimated fair value of the Company's contingent consideration owed to sellers is calculated using applicable models and inputs for each acquired entity. Other — Cash and cash equivalents, restricted cash, net accounts receivable, income tax refund receivable, and accounts payable represent financial instruments for which the carrying amount approximates fair value, as they are short-term in nature. These instruments are accordingly excluded from the disclosures below. All remaining balance sheet amounts excluded from the below are not considered financial instruments, subject to this disclosure. Fair Value Hierarchy — ASC 820 establishes a framework for measuring fair value in accordance with GAAP and expands financial statement disclosure requirements for fair value measurements. ASC 820 further specifies a hierarchy of valuation techniques, which is based on whether the inputs into the valuation technique are observable or unobservable. The hierarchy follows: • Level 1 — Valuation techniques in which all significant inputs are quoted prices from active markets for assets or liabilities that are identical to the assets or liabilities being measured. • Level 2 — Valuation techniques in which significant inputs include quoted prices from active markets for assets or liabilities that are similar to the assets or liabilities being measured and/or quoted prices from markets that are not active for assets or liabilities that are identical or similar to the assets or liabilities being measured. Also, model-derived valuations in which all significant inputs and significant value drivers are observable in active markets are Level 2 valuation techniques. • Level 3 — Valuation techniques in which one or more significant inputs or significant value drivers are unobservable. Unobservable inputs are valuation technique inputs that reflect the Company's own assumptions about the assumptions that market participants would use in pricing an asset or liability.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Property, Plant and Equipment [Table Text Block]	Depreciation of property and equipment is calculated on a straight-line basis down to the salvage value, as applicable, over the following estimated useful lives: Category: Range (in years) Revenue equipment * 3 — 20 Shop and service equipment 2 — 10 Land improvements 5 — 15 Buildings and building improvements 10 — 40 Furniture and fixtures 3 — 10 Leasehold improvements Life of the lease *For finance leases involving revenue equipment, the depreciation period is equal to the term of the lease agreement.

Recently Issued Accounting Pr_2

Recently Issued Accounting Pronouncements (Tables)	12 Months Ended
	Dec. 31, 2021
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 October 2021 ASU No. 2021-08: Business Combinations (ASC 805), Accounting for Contract Assets and Contract Liabilities from Contracts with Customers The amendments in this ASU require that the acquirer recognize and measure contract assets and contract liabilities in a business combination in accordance with ASC 606 as if the acquirer had originated the contracts. The amendments in this ASU are applied prospectively to business combinations occurring on or after the effective date of the amendments. January 2023, Prospective Currently under evaluation, but not expected to be material August 2021 ASU No. 2021-06:Presentation of Financial Statements (ASC 205), Financial Services – Depository and Lending (ASC 942), and Financial Services – Investment Companies (ASC 946) 1 The ASU amends various SEC paragraphs pursuant to the issuance of an SEC release to update disclosure requirements for financial statements from acquired and disposed businesses including changes in tests and thresholds. Additionally, the ASU amends various SEC paragraphs pursuant to an SEC release to update statistical disclosure requirements for bank and savings and loan registrants. August 2021, Adoption method varies by amendment No material impact August 2020 ASU No. 2020-06: Debt – Debt with Conversion and Other Options (ASC 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (ASC 815-40) – Accounting for Convertible Instruments and contracts in an Entity's Own Equity The amendments in this ASU add disclosure requirements to convertible debt instruments and convertible preferred stock, require convertible instruments to be disclosed at fair value, and update the calculation requirements for diluted EPS. The amendments in this ASU can be applied on a modified or fully retrospective basis and are effective for public entities for years beginning after December 15, 2021. January 2022, Modified retrospective or fully retrospective No material impact 1 Adopted during the third quarter of 2021.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2021
Business Combinations [Abstract]
ACT 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, the beginning of the comparative period presented. 2021 2020 (in thousands, except per share data) Total revenue $ 6,387,329 $ 5,374,934 Net income attributable to Knight-Swift 763,393 437,835 Earnings per share – diluted 4.57 2.57
Allocation of purchase consideration	The purchase price allocations for the Company's acquisitions are preliminary, except for Warehousing Co., and have been allocated based on estimated fair values of the assets acquired and liabilities assumed at the acquisition dates, 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 are not to exceed one year from the respective acquisition dates. MME ACT UTXL Eleos Warehousing Co. 1 December 6, 2021 Opening Balance Sheet as Reported at December 31, 2021 July 5, 2021 Opening Balance Sheet as Reported at December 31, 2021 June 1, 2021 Opening Balance Sheet as Reported at December 31, 2021 February 1, 2021 Opening Balance Sheet as Reported at December 31, 2021 January 1, 2020 Opening Balance Sheet as Reported at December 31, 2021 Fair value of the consideration transferred $ 164,382 $ 1,306,214 $ 37,230 $ 41,518 $ 66,444 Cash and cash equivalents 14,716 17,477 8,206 2,237 1,388 Trade receivables 21,915 104,220 9,451 545 3,301 Prepaid expenses 2,067 15,803 — 47 608 Other current assets 462 3,537 — — 78 Property and equipment 49,192 427,722 54 — 1,938 Operating lease right-of-use assets 52,065 4,053 — 560 12,356 Identifiable intangible assets 2 52,960 406,160 22,121 15,850 55,681 Other noncurrent assets 139 1,739 — — 458 Total assets 193,516 980,711 39,832 19,239 75,808 Accounts payable (7,681) (19,386) (14,183) (156) (347) Accrued payroll and payroll-related expenses (7,106) (33,411) (247) (605) — Accrued liabilities (544) (9,302) (69) (1,391) (644) Claims accruals – current and noncurrent portions (1,090) (40,958) (418) — — Operating lease liabilities – current and noncurrent portions (46,375) (4,052) — (560) (12,356) Long-term debt – current and noncurrent portions — (54,024) — — — Deferred tax liabilities (19,009) — — — — Other long-term liabilities (568) (4,243) — (475) — Total liabilities (82,373) (165,376) (14,917) (3,187) (13,347) Noncontrolling interest — — — (10,281) — Total stockholders' equity — — — (10,281) — Goodwill $ 53,239 $ 490,879 $ 12,315 $ 35,747 $ 3,983 1 See above for a description of the working capital adjustments made to Warehousing Co.'s purchase price allocation during the measurement period. 2 Includes $372.2 million in customer relationships ($250.8 million attributed to ACT), $2.0 million in noncompete agreements ($0.8 million attributed to ACT), $10.5 million in internally developed software ($6.5 million attributable to ACT), and $168.0 million in trade names ($148.1 million attributed to ACT).

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Amortized Cost, Gross Unrealized Gains And Losses, Estimated Fair Value Of Fixed Maturity Securities	The following table presents the cost or amortized cost, gross unrealized gains and temporary losses, and estimated fair value of the Company's restricted investments: December 31, 2021 Gross Unrealized Cost or Amortized Cost Gains Temporary Estimated Fair Value (In thousands) US corporate securities $ 5,866 $ — $ (7) $ 5,859 Restricted investments, held-to-maturity $ 5,866 $ — $ (7) $ 5,859 December 31, 2020 Gross Unrealized Cost or Amortized Cost Gains Temporary Estimated Fair Value (In thousands) US corporate securities $ 9,001 $ 2 $ (8) $ 8,995 Restricted investments, held-to-maturity $ 9,001 $ 2 $ (8) $ 8,995

Equity Investments (Tables)

Equity Investments (Tables)	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Transportation Resource Partners Investments and Commitments	The following table presents ownership and commitment information for the Company's investments in TRP partnerships: December 31, 2021 Knight-Swift's Ownership Interest 1 Total Commitment (All Partners) Knight-Swift's Contracted Commitment Knight-Swift's Remaining Commitment (Dollars in thousands) TRP III – equity method investment 3 5 6.0 % $ 245,000 $ 15,000 $ 1,692 TRP IV – equity investment 2 4 4.2 % $ 116,065 $ 4,900 $ 654 TRP IV Coinvestment NTI – equity method investment 5 — % $ 120,000 $ 10,000 $ — TRP IV Coinvestment QLS – equity method investment 25.0 % $ 39,000 $ 9,735 $ — TRP IV Coinvestment FFR – equity method investment 5 7.4 % $ 66,555 $ 4,950 $ — TRP V - equity method investment 6 16.6 % $ 180,700 $ 30,000 $ 17,803 TRP V Coinvest - equity method investment 5 6 13.3 % $ 30,000 $ 4,000 $ — 1 The Company's share of the results is included within "Other income, net" in the consolidated statements of comprehensive income. 2 In accordance with ASC 321, Investments – Equity Securities , these investments are recorded at cost minus impairment. 3 Management anticipates that $1.7 million will be due in 2022. 4 Management anticipates that the following amounts will be due: $0.1 million in 2022, $0.1 million from 2023 through 2024, $0.5 million in 2025, and none thereafter. 5 The TRP III, TRP IV Coinvestments, TRP V, and TRP V Coinvest are unconsolidated majority interests. Management considered the criteria set forth in ASC 323, Investments – Equity Method and Joint Ventures , to establish the appropriate accounting treatment for these investments. This guidance requires the use of the equity method for recording investments in limited partnerships where the "so minor" interest is not met. As such, the investments are being accounted for under the equity method. Knight's ownership interest reflects its ultimate ownership of the portfolio companies underlying the TRP III, TRP IV Coinvestment NTI, TRP IV Coninvestment QLS, TRP IV Coinvestment FFR, TRP V, and TRP V Coninvest legal entities. 6 Management anticipates that the following amounts will be due: $7.2 million in 2022, $7.2 million from 2023 through 2024, $0.9 million from 2025 through 2026, and $2.5 million thereafter.
Net Investments Carrying Value	Net investment balances included in "Other long-term assets" in the consolidated balance sheets were as follows: December 31, 2021 2020 (in thousands) TRP III – equity method investment $ 801 $ 217 TRP IV – equity investment 1 3 2,952 TRP IV Coinvestment NTI – equity method investment 37 5,609 TRP IV Coinvestment QLS – equity method investment 12,444 16,240 TRP IV Coinvestment FFR – equity method investment 6,761 4,905 TRP V – equity method investment 12,043 3,304 TRP V Coinvest – equity method investment 4,859 4,000 Holdings Co. – equity method investment 2 38,821 40,335 Embark – equity investment $ 54,467 $ — Total carrying value $ 130,236 $ 77,562 1 In accordance with ASC 321, Investments – Equity Securities , these investments are recorded at cost minus impairment. 2 In accordance with ASC 323, Investments – Equity Method and Joint Ventures, the net investment balance includes accretion of amortization of certain definite-lived intangibles.

Trade Receivables, net (Tables)

Trade Receivables, net (Tables)	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Schedule of Trade Receivables, net	Trade receivables, net balances were comprised of the following: December 31, 2021 2020 (In thousands) Trade customers $ 847,305 $ 570,611 Equipment manufacturers 11,923 5,680 Insurance premiums 1 43,455 5,804 Other 1 30,316 18,477 Trade receivables 932,999 600,572 Less: Allowance for doubtful accounts (21,663) (22,093) Trade receivables, net $ 911,336 $ 578,479 1 Prior year amounts within the table above have been reclassified to conform to current year presentation. The following is a rollforward of the allowance for doubtful accounts for trade receivables: 2021 2020 2019 (In thousands) Beginning balance $ 22,093 $ 18,178 $ 16,355 Provision 10,900 17,267 16,925 Write-offs directly against the reserve (776) (902) (2,652) Write-offs for revenue adjustments (11,504) (12,450) (12,450) Other 1 950 — — Ending balance $ 21,663 $ 22,093 $ 18,178 1 Represents allowance for doubtful trade accounts receivables assumed in 2021 from the Company's acquisitions. See Note 4 for further details regarding these acquisitions. December 31, 2021 2020 (In thousands) Notes receivable from independent contractors $ 5,969 $ 7,291 Convertible note receivable from third party 10,141 — Notes receivable from other third parties 994 3,034 Gross notes receivable 17,104 10,325 Allowance for doubtful notes receivable (496) (602) Total notes receivable, net of allowance $ 16,608 $ 9,723 Current portion, net of allowance 1,848 2,846 Long-term portion $ 14,760 $ 6,877

Notes Receivable, net (Tables)

Notes Receivable, net (Tables)	12 Months Ended
	Dec. 31, 2021
Receivables [Abstract]
Schedule of Notes Receivable	Trade receivables, net balances were comprised of the following: December 31, 2021 2020 (In thousands) Trade customers $ 847,305 $ 570,611 Equipment manufacturers 11,923 5,680 Insurance premiums 1 43,455 5,804 Other 1 30,316 18,477 Trade receivables 932,999 600,572 Less: Allowance for doubtful accounts (21,663) (22,093) Trade receivables, net $ 911,336 $ 578,479 1 Prior year amounts within the table above have been reclassified to conform to current year presentation. The following is a rollforward of the allowance for doubtful accounts for trade receivables: 2021 2020 2019 (In thousands) Beginning balance $ 22,093 $ 18,178 $ 16,355 Provision 10,900 17,267 16,925 Write-offs directly against the reserve (776) (902) (2,652) Write-offs for revenue adjustments (11,504) (12,450) (12,450) Other 1 950 — — Ending balance $ 21,663 $ 22,093 $ 18,178 1 Represents allowance for doubtful trade accounts receivables assumed in 2021 from the Company's acquisitions. See Note 4 for further details regarding these acquisitions. December 31, 2021 2020 (In thousands) Notes receivable from independent contractors $ 5,969 $ 7,291 Convertible note receivable from third party 10,141 — Notes receivable from other third parties 994 3,034 Gross notes receivable 17,104 10,325 Allowance for doubtful notes receivable (496) (602) Total notes receivable, net of allowance $ 16,608 $ 9,723 Current portion, net of allowance 1,848 2,846 Long-term portion $ 14,760 $ 6,877

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of goodwill	The changes in the carrying amounts of goodwill were as follows: 2021 2020 2019 (In thousands) Goodwill at beginning of period $ 2,922,964 $ 2,918,992 $ 2,919,176 Amortization relating to deferred tax assets (9) (11) (232) Acquisitions 1 592,180 3,983 48 Goodwill at end of period $ 3,515,135 $ 2,922,964 $ 2,918,992 1 The goodwill associated with the ACT and MME acquisitions was allocated to the LTL segment. The goodwill associated with the UTXL acquisition was allocated to the Logistics segment. The goodwill associated with the Warehousing Co, and Eleos acquisitions was allocated to the non-reportable segments. See Note 4 regarding the amount attributed to adjustments to the opening balance sheets. The following presents the components of goodwill by reportable segment as of December 31, 2021 and 2020: December 31, 2021 2020 Net Carrying Amount 1 Net Carrying Amount 1 (In thousands) Truckload $ 2,658,086 $ 2,658,095 Logistics 54,827 42,512 LTL 544,118 — Intermodal 175,594 175,594 Non-reportable 82,510 46,763 Goodwill $ 3,515,135 $ 2,922,964 1 Except for the net accumulated amortization related to deferred tax assets in the Truckload segment, the net carrying amount and gross carrying amount are equal since there are no accumulated impairment losses.
Schedule of Intangible Assets, net	Other intangible asset balances were as follows: December 31, 2021 2020 (In thousands) Definite-lived intangible assets: 1 Gross carrying amount $ 1,227,630 $ 894,597 Accumulated amortization (201,139) (145,852) Definite-lived intangible assets, net 1,026,491 748,745 Indefinite-lived trade names: Gross carrying amount 804,558 640,500 Intangible assets, net $ 1,831,049 $ 1,389,245 1 The major categories of the Company's definite-lived intangible assets include customer relationships, non-compete agreements, internally-developed software, trade names, and others. Identifiable intangible assets subject to amortization have been recorded at fair value. Intangible assets related to acquisitions other than the 2017 Merger are amortized over a weighted-average amortization period of 19.0 years. The Company's customer relationship intangible assets related to the 2017 Merger are being amortized over a weighted average amortization period of 19.9 years.
Finite-lived Intangible Assets Amortization Expense	The following table presents amortization of intangible assets related to the 2017 Merger and various acquisitions: 2021 2020 2019 (In thousands) Amortization of intangible assets related to the 2017 Merger $ 41,375 $ 41,375 $ 41,375 Amortization related to other intangible assets 13,924 4,520 1,501 Amortization of intangibles $ 55,299 $ 45,895 $ 42,876

Accrued Payroll and Purchased_2

Accrued Payroll and Purchased Transportation and Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Payables and Accruals [Abstract]
Schedule of Accrued Payroll and Purchased Transportation	The following table presents the composition of accrued payroll and purchased transportation: December 31, 2021 2020 (In thousands) Accrued payroll 1 $ 146,326 $ 114,835 Accrued purchased transportation 70,758 46,053 Accrued payroll and purchased transportation $ 217,084 $ 160,888 1 Accrued payroll includes accruals related to the various 401(k) plans the Company offers to its employees. Depending on the plan, employees must meet the minimum age requirement (18 – 21 years) and have completed ninety days or one year of service with the Company in order to qualify. Employees' rights to employer contributions are fully vested after three or five years from their date of employment. The plans offer discretionary matching contributions of the greater of 100% up to 3.0% or 6.0% of an employee's eligible compensation or $2,000. The Company's employee benefits expense for matching contributions related to the 401(k) plans was approximately $16.2 million, $13.6 million, and $8.8 million in 2021, 2020, and 2019, respectively. This expense was included in "Salaries, wages, and benefits" in the consolidated statements of comprehensive income. As of December 31, 2021 and 2020, the balance above in accrued payroll included $14.5 million and $12.8 million, respectively, in matching contributions for the 401(k) plans.

Claims Accruals (Tables)

Claims Accruals (Tables)	12 Months Ended
	Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Abstract]
Schedule of Claims Accruals	Claims accruals were comprised of the following: December 31, 2021 2020 (In thousands) Auto reserves $ 263,091 $ 231,875 Workers’ compensation reserves 90,481 94,609 Third-party carrier claims reserves 31,524 40 Independent contractor claims reserves 6,285 7,112 Cargo damage reserves 5,409 2,494 Employee medical and other reserves 20,531 13,612 Claims accruals 417,321 349,742 Less: current portion of claims accruals (206,607) (174,928) Claims accruals, less current portion $ 210,714 $ 174,814

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Tax Expense (Benefit)	The following table presents the Company's income tax expense: 2021 2020 2019 (In thousands) Current expense: Federal $ 140,258 $ 80,060 $ 50,703 State 42,319 19,153 16,616 Foreign 8,382 4,248 5,526 190,959 103,461 72,845 Deferred expense (benefit): Federal 48,874 29,640 28,618 State (10,369) 7,292 3,712 Foreign 1,423 9,283 (1,377) 39,928 46,215 30,953 Income tax expense $ 230,887 $ 149,676 $ 103,798
Schedule Of Effective Income Tax Rate Reconciliation	Actual tax expense differs from expected tax expense as follows: 2021 2020 2019 (In thousands) Computed "expected" tax expense $ 204,673 $ 117,665 $ 86,935 Increase (decrease) in income taxes resulting from: State income taxes, net of federal income tax benefit 23,063 22,423 17,803 Other 3,151 9,588 (940) Income tax expense $ 230,887 $ 149,676 $ 103,798
Components Of Net Deferred Tax Asset (Liability)	The components of the net deferred tax asset (liability) included in "Deferred tax liabilities" in the consolidated balance sheets were: December 31, 2021 2020 (In thousands) Deferred tax assets: Claims accrual $ 79,496 $ 81,426 Allowance for doubtful accounts 5,530 5,727 Amortization of stock options 8,192 7,712 Accrued liabilities 11,497 17,941 Operating lease liabilities 34,260 29,278 Other 20,562 10,687 Total deferred tax assets 159,537 152,771 Valuation allowance — — Total deferred tax assets, net 159,537 152,771 Deferred tax liabilities: Property and equipment, principally due to differences in depreciation (635,877) (586,349) Prepaid taxes, licenses, and permits deducted for tax purposes (15,241) (12,629) Intangible assets (338,191) (334,618) Operating lease right-of-use assets (34,016) (28,259) Other (11,089) (6,857) Total deferred tax liabilities (1,034,414) (968,712) Deferred income taxes $ (874,877) $ (815,941)
Reconciliation Of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits for 2021, 2020, and 2019 is below: 2021 2020 2019 (In thousands) Unrecognized tax benefits at beginning of year $ 2,950 $ 4,083 $ 7,423 Increases for tax positions taken prior to beginning of year — — 38 Decreases for tax positions taken prior to beginning of year (1,215) (1,133) (3,378) Unrecognized tax benefits at end of year $ 1,735 $ 2,950 $ 4,083

Accounts Receivable Securitiz_2

Accounts Receivable Securitization (Tables)	12 Months Ended
	Dec. 31, 2021
Transfers and Servicing of Financial Assets [Abstract]
Accounts Receivable Securitization [Table Text Block]	The following table summarizes the key terms of the 2021 RSA and 2018 RSA (dollars in thousands): 2021 RSA 2018 RSA (Dollars in thousands) Effective April 23, 2021 July 11, 2018 Final maturity date April 23, 2024 July 9, 2021 Borrowing capacity $400,000 $325,000 Accordion option 1 $100,000 $175,000 Unused commitment fee rate 2 20 to 40 basis points 20 to 40 basis points Program fees on outstanding balances 3 4 one month LIBOR + 82.5 basis points one month LIBOR + 80 to 100 basis points 1 The accordion option increases the maximum borrowing capacity, subject to participation by the purchasers. 2 The 2021 RSA and 2018 RSA commitment fee rates are based on the percentage of the maximum borrowing capacity utilized. 3 Only the rate for the 2018 RSA program fee is subject to the Company's consolidated total net leverage ratio. 4 As identified within the 2021 RSA, the lender can trigger an amendment by identifying and deciding upon a replacement index for LIBOR. Availability under the 2021 RSA and 2018 RSA is calculated as follows: December 31, 2021 2020 (In thousands) Borrowing base, based on eligible receivables $ 400,000 $ 302,700 Less: outstanding borrowings 1 (279,000) (214,000) Less: outstanding letters of credit (65,300) (67,281) Availability under accounts receivable securitization facilities $ 55,700 $ 21,419 1 As of December 31, 2021, outstanding borrowings are included in "Accounts receivable securitization – less current portion" in the consolidated balance sheets and are offset by $0.5 million of deferred loan costs. As of December 31, 2020, outstanding borrowings are included in "Accounts receivable securitization – current portion" in the consolidated balance sheets and are offset by $0.1 million of deferred loan costs. Interest accrued on the aggregate principal balance at a rate of 0.9% and 1.0%, as of December 31, 2021 and 2020, respectively.

Debt And Financing (Tables)

Debt And Financing (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule of Debt Balances by Instrument [Table Text Block]	Other than the Company's accounts receivable securitization as discussed in Note 14 and its outstanding finance lease obligations as discussed in Note 16, the Company's long-term debt consisted of the following: December 31, 2021 2020 (In thousands) 2021 Term Loan A-1, due December 3 2022, net 1 2 $ 199,676 $ — 2021 Term Loan A-2, due September 3, 2024, net 1 2 199,607 — 2021 Term Loan A-3, due September 3, 2026, net 1 2 798,352 — 2017 Term Loan, due October 2022, net 1 3 — 298,907 Prudential Notes, net 1 47,265 — Other 5,069 — Total long-term debt, including current portion 1,249,969 298,907 Less: current portion of long-term debt (212,417) — Long-term debt, less current portion $ 1,037,552 $ 298,907 December 31, 2021 2020 (In thousands) Total long-term debt, including current portion $ 1,249,969 $ 298,907 2021 Revolver, due September 3, 2026 1 4 260,000 — 2017 Revolver, due October 2022 1 5 — 210,000 Long-term debt, including revolving line of credit $ 1,509,969 $ 508,907 1 Refer to Note 23 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 $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 3 Net of $1.1 million in deferred loan costs at December 31, 2020. 4 The Company also had outstanding letters of credit of $64.0 million under the 2021 Revolver, primarily related to workers' compensation and self-insurance liabilities, at December 31, 2021.
Schedule of Debt Terms [Table Text Block]	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 margin reference rate 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 Loan and 2021 Revolver is based on the Company's consolidated leverage ratio. As of December 31, 2021, interest accrued at 1.022% on the 2021 Term Loans and 1.064% 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 0.07% to 0.20%. As of December 31, 2021, commitment fees on the unused portion of the 2021 Revolver accrued at 0.100% and outstanding letter of credit fees accrued at 1.000%.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Lease Cost	The components of the Company's lease cost were as follows: 2021 2020 (in thousands) Operating lease cost: Operating lease costs $ 46,795 $ 80,456 Short-term lease cost ¹ 8,426 6,544 Sublease income (60) (360) Rental expense 55,161 86,640 Finance lease cost: Amortization of property and equipment 37,659 16,638 Interest expense 5,232 2,896 Total finance lease cost 42,891 19,534 Total operating and finance lease costs $ 98,052 $ 106,174 1 Short-term lease cost includes leases with a term of twelve months or less, as well as month-to-month leases and variable lease costs.
Lease Liability Calculation Assumptions	The assumptions underlying the calculation of the Company's right-of-use assets and corresponding lease liabilities are disclosed below. December 31, 2021 2020 Operating Finance Operating Finance Revenue equipment leases Weighted average remaining lease term 1.6 years 4.0 years 2.0 years 3.6 years Weighted average discount rate 2.3 % 1.9 % 2.4 % 2.4 % Real estate and other leases Weighted average remaining lease term 12.6 years — 10.6 years — Weighted average discount rate 3.0 % — % 3.7 % — %
Maturity analysis of Lease Liabilities (as Lessee)	Future minimum lease payments for all noncancelable leases were: December 31, 2021 Operating Finance (In thousands) 2022 $ 38,871 $ 54,741 2023 27,124 49,275 2024 15,084 91,115 2025 11,037 70,543 2026 8,793 9,839 Thereafter 71,007 45,185 Future minimum lease payments 171,916 320,698 Less: amounts representing interest (28,980) (14,526) Present value of minimum lease payments 142,936 306,172 Less: current portion (35,322) (50,006) Lease liabilities – less current portion $ 107,614 $ 256,166
Supplemental Cash Flow (Leases)	The following table sets forth cash paid for amounts included in the measurement of lease liabilities: 2021 2020 (in thousands) Operating cash flows for operating leases $ 48,171 $ 83,675 Operating cash flows for finance leases 5,232 2,896 Financing cash flows for finance leases 108,186 83,910
Lease Revenue and Rental Income	The components of the Company's lease revenue are included in "Revenue, excluding truckload and LTL fuel surcharge" and the Company's rental income is included in "Other income, net" in the consolidated statements of comprehensive income. These amounts are disclosed in the table below. 2021 2020 (in thousands) Operating lease revenue $ 95,934 $ 45,698 Variable lease revenue 1,353 1,691 Total lease revenue 1 $ 97,287 $ 47,389 Rental income 2 $ 10,375 $ 10,365 1 Represents operating revenue earned by the Company for leasing equipment to independent contractors and other third-parties. 2 Represents non-operating income earned from leasing real estate to third parties.
Maturity Analysis of Lease Receivables (as Lessor)	Future minimum lease revenues for all noncancelable leases were: December 31, 2021 (In thousands) 2022 $ 38,262 2023 26,211 2024 12,492 2025 5,215 2026 1,926 Thereafter 3,618 Future minimum lease revenues $ 87,724

Defined Benefit Pension Plan (T

Defined Benefit Pension Plan (Tables)	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Schedule of Amounts Recognized in Balance Sheet	The net pension liability recognized is as follows: December 31, 2021 (In thousands) Projected benefit obligation $ 71,440 Less: fair value of plan assets 70,467 Unfunded status $ 973 Accrued pension liability recognized 1 $ 973
Schedule of Defined Benefit Plans Disclosures	Other information concerning the defined benefit pension plan is summarized below: 2021 (In thousands) Net periodic pension income $ 1,483 Benefits paid 2,981 The following benefit payments are expected to be paid in each of the fiscal years as follows: December 31, 2021 (In thousands) 2022 3,594 2023 3,708 2024 3,854 2025 3,956 2026 4,043 2027 through 2030 20,543 Total $ 39,698
Defined Benefit Plan, Assumptions	The following weighted-average assumptions were used to determine net periodic pension cost: 2021 Discount rate 2.55 % Expected long-term rate of return on pension plan assets 6.00 %
Defined Benefit Plan, Plan Assets, Allocation	The defined benefit pension plan weighted-average asset allocations, by asset category, are as follows: 2021 Asset category: Equity securities 30 % Debt securities 68 % Cash and cash equivalents 2 % Total 100 % The target allocation by asset category, is as follows: 2021 Asset category: Equity securities 30 % Debt securities 70 % Total 100 %

Contingencies and Legal Proce_3

Contingencies and Legal Proceedings (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Loss Contingencies by Contingency [Table Text Block]	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 consolidated balance sheets. The Company has recorded an aggregate accrual of approximately $18.1 million and $20.2 million relating to the Company's outstanding legal proceedings as of December 31, 2021 and 2020, respectively. 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 CRST Expedited The plaintiff alleges tortious interference with contract and unjust enrichment related to non-competition agreements entered into with certain of its drivers. Plaintiff(s) Defendant(s) Date instituted Court or agency currently pending in CRST Expedited, Inc. Swift Transportation Co. of Arizona LLC. March 20, 2017 United States District Court for the Northern District of Iowa Recent Developments and Current Status In July 2019, a jury issued an adverse verdict in this lawsuit. The court issued a decision granting in part and denying in part certain motions related to the jury’s verdict. Both parties have appealed the court’s decision. On August 6, 2021 a three-judge panel of the 8th Circuit Court of Appeals issued an opinion reversing the trial court’s decision. On October 4, 2021 the 8th Circuit Court of Appeals denied a petition for rehearing. The likelihood that a loss has been incurred is no longer probable, and the accrual for this lawsuit has accordingly been reversed as of December 31, 2021. 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 December 31, 2021. 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 FLSA 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 Unites 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 December 31, 2021, 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)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 Board Approval Date Authorized Amount Shares Amount Shares Amount (in thousands) May 30, 2019 $250,000 — — 4,841 179,585 November 24, 2020 1 $250,000 1,377 57,175 — — 1,377 $ 57,175 4,841 $ 179,585 1 $192.8 million and $250.0 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of December 31, 2021 and December 31, 2020, respectively

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Compensation Expense Related To Stock-Based Compensation	Stock-based compensation expense, net of forfeitures, which is included in "Salaries, wages, and benefits" in the consolidated statements of comprehensive income is comprised of the following: 2021 2020 2019 (In thousands) Stock options $ 232 $ 567 $ 1,149 Restricted stock units 18,190 13,496 9,734 Performance units 15,073 5,576 2,492 Stock-based compensation expense – equity awards $ 33,495 $ 19,639 $ 13,375 Stock-based compensation (benefit) expense – liability awards 1 (5,364) 6,955 2,663 Total stock-based compensation expense, net of forfeitures $ 28,131 $ 26,594 $ 16,038 Income tax benefit 2 $ 8,357 $ 4,949 $ 3,344 1 Includes awards granted to executive management in November 2019 that, per the original agreement, would ultimately settle in cash upon fulfilling a requisite service period (for restricted stock units) and fulfilling a requisite service period and achieving performance targets (for performance units). During 2021, the Company amended the agreements for outstanding awards to ultimately settle in shares after each requisite service period. 2 The income tax benefit is calculated by applying the statutory tax rate to stock-based compensation expense for equity awards, as the expense associated with liability awards is not tax deductible.
Share-based Payment Arrangement, Nonvested Award, Cost [Table Text Block]	The following table presents the total unrecognized stock-based compensation expense and the expected weighted average period over which these expenses will be recognized: December 31, 2021 Expense Weighted Average Period (In thousands) (In years) Equity awards – Restricted stock units 49,704 2.2 Equity awards – Performance units 14,306 2.4 Total unrecognized stock-based compensation expense $ 64,010 2.3
Schedule of Grants of Restricted Stock [Table Text Block]	2021 2020 2019 Restricted stock units 562,021 722,499 588,819 Performance units 112,690 146,036 102,776 Equity awards granted 674,711 868,535 691,595 Liability awards granted 1 2 — — 80,927 Total stock awards granted 674,711 868,535 772,522 1 Includes 48,556 performance units in 2019. 2 Includes 32,371 restricted stock units in 2019.
Summary Of Activity Related To Stock Options	A summary of 2021 stock option activity follows: Stock options outstanding: Shares Under Option Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value 1 (In years) (In thousands) Stock options outstanding at December 31, 2020 302,976 $ 29.45 1.2 $ 3,748 Granted — — Exercised (207,242) 28.59 Expired (7,419) 23.80 Forfeited (3,308) 33.35 Stock options outstanding at December 31, 2021 85,007 $ 31.95 0.6 $ 2,464 Aggregate number of stock options expected to vest at a future date as of December 31, 2021 — $ — 0.0 $ — Exercisable at December 31, 2021 85,007 $ 31.95 0.6 $ 2,464 1 The aggregate intrinsic value was computed using the closing share price on December 31, 2021 of $60.94 and on December 31, 2020 of $41.82, as applicable.
Summary Of Exercise Of Stock Options	The following table summarizes stock option exercise information for the years presented: Stock option exercises 2021 2020 2019 (In thousands, except share data) Number of stock options exercised 207,242 382,254 443,288 Intrinsic value of stock options exercised $ 4,120 $ 4,929 $ 5,183 Cash received upon exercise of stock options $ 5,924 $ 10,199 $ 10,478 Income tax benefit $ 1,304 $ 1,029 $ 221
Rollforward of Company's Nonvested Stock Options	The following table is a rollforward of the Company's unvested stock options: Unvested stock options: Shares Weighted Average Fair Value Unvested stock options at December 31, 2020 86,779 $ 6.78 Vested (83,707) 6.78 Forfeited and canceled (3,072) 6.78 Unvested stock options at December 31, 2021 — $ —
Rollforward of Nonvested Restricted Stock Awards [Table Text Block]	The following table is a rollforward of unvested restricted stock units, including restricted stock units classified as equity and those classified as liabilities: Unvested restricted stock units: Number of Awards Weighted Average Fair Value 1 Unvested restricted stock units at December 31, 2020 1,723,838 $ 34.07 Granted 562,021 50.63 Vested 2 (456,670) 32.53 Forfeited (119,428) 39.97 Unvested restricted stock units at December 31, 2021 1,709,761 $ 39.81 1 The fair value of each restricted stock unit is based on the closing market price on the grant date. 2 Includes 170,280 shares withheld for taxes and 18,697 net units settled in cash which were excluded from the "Common stock issued to employees" activity within the consolidated statements of stockholders' equity.
Rollforward of Nonvested Performance Shares [Table Text Block]	The following table is a rollforward of unvested performance units, including performance units classified as equity and those classified as liabilities: Unvested performance units: Shares Weighted Average Fair Value Unvested performance units at December 31, 2020 549,730 $ 39.50 Granted 112,690 $ 60.55 Shares earned above target 45,409 $ 37.89 Vested 1 (136,225) $ 45.02 Unvested performance units at December 31, 2021 2 571,604 $ 44.22 1 Includes 63,815 shares withheld for taxes and 39,225 net units settled in cash which were excluded from the "Common stock issued to employees" activity within the consolidated statements of stockholders' equity. 2 The performance measurement period for performance units granted in 2018 is January 1, 2019 to December 31, 2021 (three full calendar years). The performance measurement period for performance units granted in 2019 is January 1, 2020 to December 31, 2022 (three full calendar years). The performance measurement period for performance units granted in 2020 is January 1, 2021 to December 31, 2023 (three full calendar years). The performance measurement period for units granted in 2021 is January 1, 2022 to December 31, 2024 (three full calendar years). All performance units will vest one month following the expiration of the performance measurement period.
Performance unit fair value assumptions	The following table presents the weighted average assumptions used in the fair value computation for performance units, including performance units classified as equity and those classified as liabilities: Performance unit fair value assumptions: 2021 2020 2019 Dividend yield 1 0.67 % 0.78 % 0.66 % Expected volatility 2 36.00 % 37.99 % 34.88 % Average peer volatility 2 35.49 % 35.62 % 27.96 % Average peer correlation coefficient 3 0.60 0.59 0.60 Risk-free interest rate 4 0.92 % 0.20 % 1.60 % Expected term (in years) 5 3.1 3.1 3.1 Weighted-average fair value of performance units granted $ 60.55 $ 42.41 $ 37.24 1 The dividend yield, used to project stock price to the end of the performance period, is based on the Company's historical experience and future expectation of dividend payouts. Total stockholder return is determined assuming that dividends are reinvested in the issuing entity over the performance period, which is mathematically equivalent to utilizing a 0% dividend yield. 2 Management (or peer company) estimated volatility using the Company's (or peer company's) historical share price performance over the remaining performance period as of the grant date. 3 The correlation coefficients are used to model the way in which each entity tends to move in relation to each other; the correlation assumptions were developed using the same stock price data as the volatility assumptions. 4 The risk-free interest rate assumption is based on US Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the performance award. 5 Since the Monte Carlo Simulation valuation is an open form model that uses an expected life commensurate with the performance period, the expected life of the performance units was assumed to be the period from the grant date to the end of the performance period.

Weighted Average Shares Outst_2

Weighted Average Shares Outstanding (Tables)	12 Months Ended
	Dec. 31, 2021
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: 2021 2020 2019 (In thousands) Basic weighted average common shares outstanding 165,860 169,711 171,541 Dilutive effect of equity awards 1,200 838 601 Diluted weighted average common shares outstanding 167,060 170,549 172,142 Anti-dilutive shares excluded from earnings per diluted share 1 208 63 603 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.

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2021
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: December 31, 2021 December 31, 2020 Consolidated Balance Sheets Caption Carrying Estimated Carrying Estimated (In thousands) Financial Assets: Restricted investments, held-to-maturity 1 Restricted investments, held-to-maturity, amortized cost $ 5,866 $ 5,859 $ 9,001 $ 8,995 Equity method investments Other long-term assets 75,769 75,769 77,562 77,562 Investments in equity securities Other long-term assets 74,201 74,201 18,675 18,675 Convertible note Other long-term assets 10,141 10,141 — — Financial Liabilities: 2021 Term Loan A-1, due December 2022 2 Long-term debt – less current portion 199,676 200,000 — — 2021 Term Loan A-2, due September, 2024 2 Long-term debt – less current portion 199,607 200,000 — — 2021 Term Loan A-3, due September 2026 2 Long-term debt – less current portion 798,352 800,000 — — 2021 Revolver, due September 2026 Revolving line of credit 260,000 260,000 — — 2021 Prudential Notes 3 Finance lease liabilities and long-term debt 47,265 47,354 — — 2021 RSA, due April 2024 4 Accounts receivable securitization 278,483 279,000 — — Contingent consideration associated with acquisition Accrued liabilities, Other long-term liabilities 13,100 13,100 16,200 16,200 2017 Term Loan, due October 2022 5 Long-term debt – less current portion $ — $ — $ 298,907 $ 300,000 2017 Revolver, due October 2022 Revolving line of credit — — 210,000 210,000 2018 RSA, due July 2021 6 Accounts receivable securitization — — 213,918 214,000 1 Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity. 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 $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively. 3 The carrying amount of the 2021 Prudential Notes is net of $0.1 million in deferred loan costs and $2.4 million in fair value adjustments as of December 31, 2021 . 4 The carrying amount of the 2021 RSA is net of $0.5 million in deferred loan costs as of December 31, 2021. 5 The carrying amount of the 2017 Term Loan is net of $1.1 million in deferred loan costs as of December 31, 2020
Recurring 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 recurring basis as of December 31, 2021 and 2020: Fair Value Measurements at Reporting Date Using Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Unrealized Gain Position (In thousands) As of December 31, 2021 Convertible note 1 $ 10,141 $ — $ — $ 10,141 $ 141 Investments in equity securities 2 74,201 74,201 — — 14,456 As of December 31, 2020 Investments in equity securities 3 18,675 18,675 — — 3,553 1 The Company recognized $0.1 million of unrealized gains on the convertible note during 2021, which is included within "Other income, net" within the consolidated statements of comprehensive income. 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 income, net" within the consolidated statements of comprehensive income. During 2021, the Company recognized $16.4 million in gains on these investments in equity securities, consisting of $10.9 million in unrealized gains and $5.5 million in realized gains. 3 Fair value activity from the investments in equity securities is recorded in "Other income, net" within the consolidated statements of comprehensive income. During 2020, the Company recognized $3.7 million in unrealized gains on these investments in equity securities. Fair Value Measurements at Reporting Date Using: Estimated Level 1 Inputs Level 2 Inputs Level 3 Inputs (In thousands) 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 December 31, 2021 and 2020. Fair Value Measurements at Reporting Date Using Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Gain (Loss) (In thousands) As of December 31, 2021 Contingent consideration associated with acquisition 1 $ 13,100 $ — $ — $ 13,100 $ — As of December 31, 2020 Contingent consideration associated with acquisition 2 16,200 — — 16,200 (6,730) 1 The Company did not recognize any gains (losses) during 2021 related to the revaluation of these liabilities. Refer to Note 4 for information regarding the components of these liabilities. 2 During the fourth quarter of 2020, the Company increased the estimated fair value of the remaining contingent consideration representing the final two annual payments, resulting in a $6.7 million fair value adjustment of the deferred earnout, which was recorded in “Miscellaneous operating expenses” in the consolidated statement of comprehensive income.
Assets That Were Measured At Estimated Fair Value On Non-Recurring Basis	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 nonrecurring basis as of December 31, 2021 and 2020: Fair Value Measurements at Reporting Date Using Estimated Fair Value Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Loss (In thousands) As of December 31, 2021 Equipment 1 $ — $ — $ — $ — $ (299) As of December 31, 2020 Equipment 2 5,851 — 5,851 — (5,335) 1 Reflects the non-cash impairment of certain revenue equipment held for sale (within the non-reportable segments and the Truckload segment). 2 Reflects the non-cash impairment of certain alternative fuel technology (within the non-reportable segments) and certain revenue equipment held for sale (within the Truckload segment). The Company recognized $5.3 million of impairments during 2020.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	The following table presents Knight-Swift's transactions with companies controlled by and/or affiliated with its related parties: 2021 2020 2019 Provided by Knight-Swift Received by Knight-Swift Provided by Knight-Swift Received by Knight-Swift Provided by Knight-Swift Received by Knight-Swift (In thousands) Freight Services: Central Freight Lines 1 $ — $ — $ 7,837 $ — $ 19,651 $ — SME Industries 1 — — 56 — 345 — Total $ — $ — $ 7,893 $ — $ 19,996 $ — Facility and Equipment Leases: Central Freight Lines 1 $ — $ — $ 48 $ 277 $ 322 $ 369 Other Affiliates 1 — 311 11 229 18 — Total $ — $ 311 $ 59 $ 506 $ 340 $ 369 Other Services: Central Freight Lines 1 $ — $ — $ 427 $ — $ 1,834 $ — DPF Mobile 1 — — — 33 — 220 Other Affiliates 1 31 35 15 35 39 2,432 Total $ 31 $ 35 $ 442 $ 68 $ 1,873 $ 2,652 1 Entities affiliated with former Board member Jerry Moyes include Central Freight Lines, SME Industries, and DPF Mobile. "Other 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. • Freight Services Provided by Knight-Swift — The Company charges each of these companies for transportation services. • Freight Services Received by Knight-Swift — Transportation services received from Central Freight represent less-than-truckload freight services rendered to haul parts and equipment to Company shop locations. • Other Services Provided by Knight-Swift — Other services provided by the Company to the identified related parties include equipment sales and miscellaneous services. • Other Services Received by Knight-Swift — Consulting fees, diesel particulate filter cleaning, sales of various parts and tractor accessories, and certain third-party payroll and employee benefits administration services from the identified related parties are included in other services received by the Company. During the quarter ended September 30, 2020, the ownership percentage of Jerry Moyes and related affiliates fell below the threshold requiring related party disclosure. The amounts included in this Note 24 pertain to transactions that occurred prior to the date that the ownership percentage changed. Receivables and payables pertaining to related party transactions were: December 31, 2021 2020 Receivable Payable Receivable Payable (In thousands) Central Freight Lines $ — $ — $ 133 $ — DPF Mobile — — — 41 Other Affiliates 14 44 2 10 Total $ 14 $ 44 $ 135 $ 51

Information by Segment, Geogr_2

Information by Segment, Geography, and Customer Concentration (Tables)	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Summary Of Financial Information By Segments	The following tables present the Company's financial information by segment: 2021 2020 2019 Total revenue: (Dollars in thousands) Truckload $ 4,098,005 68.3 % $ 3,786,030 81.0 % $ 3,952,866 81.6 % Logistics $ 817,003 13.6 % $ 375,841 8.0 % $ 352,988 7.3 % LTL $ 396,308 6.6 % $ — — % $ — — % Intermodal $ 458,867 7.7 % $ 391,462 8.4 % $ 455,466 9.4 % Subtotal $ 5,770,183 96.2 % $ 4,553,333 97.4 % $ 4,761,320 98.3 % Non-reportable segments $ 306,414 5.1 % $ 188,882 4.0 % $ 130,782 2.7 % Intersegment eliminations $ (78,578) (1.3 %) $ (68,352) (1.4 %) $ (48,152) (1.0 %) Total revenue $ 5,998,019 100.0 % $ 4,673,863 100.0 % $ 4,843,950 100.0 % 2021 2020 2019 Operating income (loss): (Dollars in thousands) Truckload $ 784,436 81.2 % $ 578,512 102.5 % $ 468,749 109.7 % Logistics $ 93,920 9.7 % $ 20,245 3.6 % $ 21,869 5.1 % LTL $ 31,169 3.2 % $ — — % $ — — % Intermodal $ 42,060 4.4 % $ (943) (0.2 %) $ 4,501 1.1 % Subtotal $ 951,585 98.5 % $ 597,814 105.9 % $ 495,119 115.9 % Non-reportable segments $ 14,112 1.5 % $ (33,376) (5.9 %) $ (67,681) (15.9 %) Operating income $ 965,697 100.0 % $ 564,438 100.0 % $ 427,438 100.0 % 2021 2020 2019 Depreciation and amortization of property and equipment: (Dollars in thousands) Truckload $ 422,558 80.9 % $ 390,417 84.7 % $ 355,270 84.6 % Logistics $ 1,357 0.3 % $ 829 0.2 % $ 728 0.2 % LTL $ 24,844 4.8 % $ — — % $ — — % Intermodal $ 15,345 2.9 % $ 14,377 3.1 % $ 13,506 3.2 % Subtotal $ 464,104 88.9 % $ 405,623 88.0 % $ 369,504 88.0 % Non-reportable segments $ 58,492 11.1 % $ 55,152 12.0 % $ 50,578 12.0 % Consolidated depreciation and amortization of property and equipment $ 522,596 100.0 % $ 460,775 100.0 % $ 420,082 100.0 %

Introduction and Basis of Pre_3

Introduction and Basis of Presentation (Description of Business) (Details)	12 Months Ended
	Dec. 31, 2021VehicleSegment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number Of Company Operated National Terminal Network And Tractor Fleet	18,019
Number Of Tractors Driven By Company Drivers	16,166
Number Of Owner Operator Tractors	1,853
Number Of Fleet Of Trailers	67,606
Number of LTL tractors	2,735
Number of LTL trailers	7,413
Number Of Intermodal Tractors	597
Number Of Intermodal Containers	10,847
Number of Reportable Segments | Segment	4

Introduction and Basis of Pre_4

Introduction and Basis of Presentation (2017 Merger and Recent Acquisitions) (Details)	Dec. 06, 2021	Jul. 05, 2021	Jun. 01, 2021	Feb. 01, 2021	Jan. 01, 2020	Sep. 08, 2017
MME
Business Acquisition [Line Items]
Percentage of equity interests acquired	100.00%
Business Acquisition, Effective Date of Acquisition	Dec. 6, 2021
ACT
Business Acquisition [Line Items]
Percentage of equity interests acquired		100.00%
Business Acquisition, Effective Date of Acquisition		Jul. 5, 2021
UTXL
Business Acquisition [Line Items]
Percentage of equity interests acquired			100.00%
Business Acquisition, Effective Date of Acquisition			Jun. 1, 2021
Eleos
Business Acquisition [Line Items]
Percentage of equity interests acquired				79.44%
Business Acquisition, Effective Date of Acquisition				Feb. 1, 2021
Warehousing Co
Business Acquisition [Line Items]
Percentage of equity interests acquired					100.00%
Business Acquisition, Effective Date of Acquisition					Jan. 1, 2020
Knight Transportation Company [Member]
Business Acquisition [Line Items]
Ownership Percentage, Shares Outstanding						46.00%
Swift Transportation Company [Member]
Business Acquisition [Line Items]
Ownership Percentage, Shares Outstanding						54.00%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2021Segment
Number of Reportable Segments	4
Percentage Of Income Tax Positions Likely To Be Realized	50.00%
Customer Relationships [Member] | Minimum [Member]
Finite-Lived Intangible Asset, Useful Life	3 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived Intangible Asset, Useful Life	20 years
Revenue Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years	[1]
Revenue Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	20 years	[1]
Shop and service equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	2 years
Shop and service equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	5 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	15 years
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	10 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	40 years
Furniture and Fixtures [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years
[1]	*For finance leases involving revenue equipment, the depreciation period is equal to the term of the lease agreement.

Recently Issued Accounting Pr_3

Recently Issued Accounting Pronouncements (Details)	12 Months Ended
	Dec. 31, 2021
Accounting Standards Update 2021-08
Recently Issued Accounting Pronouncements [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Description	The amendments in this ASU require that the acquirer recognize and measure contract assets and contract liabilities in a business combination in accordance with ASC 606 as if the acquirer had originated the contracts. The amendments in this ASU are applied prospectively to business combinations occurring on or after the effective date of the amendments.
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
Accounting Standards Update 2021-06
Recently Issued Accounting Pronouncements [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Description	The ASU amends various SEC paragraphs pursuant to the issuance of an SEC release to update disclosure requirements for financial statements from acquired and disposed businesses including changes in tests and thresholds. Additionally, the ASU amends various SEC paragraphs pursuant to an SEC release to update statistical disclosure requirements for bank and savings and loan registrants.	[1]
New Accounting Pronouncement Adoption Method and Date	August 2021, Adoption method varies by amendment	[1]
New Accounting Pronouncement Financial Statement Impact	No material impact	[1]
Accounting Standards Update 2020-06
Recently Issued Accounting Pronouncements [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Description	The amendments in this ASU add disclosure requirements to convertible debt instruments and convertible preferred stock, require convertible instruments to be disclosed at fair value, and update the calculation requirements for diluted EPS. The amendments in this ASU can be applied on a modified or fully retrospective basis and are effective for public entities for years beginning after December 15, 2021.
New Accounting Pronouncement Adoption Method and Date	January 2022, Modified retrospective or fully retrospective
New Accounting Pronouncement Financial Statement Impact	No material impact
[1]	Adopted during the third quarter of 2021.

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - USD ($)		Dec. 31, 2021	Dec. 06, 2021	Jul. 05, 2021	Jun. 01, 2021	Feb. 01, 2021	Jan. 01, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Total revenue								$ 5,998,019,000	$ 4,673,863,000	$ 4,843,950,000
Net Income								743,748,000	410,635,000	310,178,000
Amortization of Intangible Assets								55,299,000	45,895,000	42,876,000
Business Combination, Contingent Consideration, Liability		$ 13,100,000						13,100,000	16,200,000
Contingent consideration associated with acquisition								6,250,000	16,200,000	$ 0
MME
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Dec. 6, 2021
Percentage of equity interests acquired			100.00%
Fair value of the consideration transferred		164,382,000	$ 164,400,000
MME | Cash paid for acquisition
Business Acquisition [Line Items]
Fair value of the consideration transferred			104,000,000
MME | Consideration for Debt Payments [Member]
Business Acquisition [Line Items]
Fair value of the consideration transferred			60,400,000
MME | Escrow For Sellers Indemnification Obligations [Member]
Business Acquisition [Line Items]
Fair value of the consideration transferred			$ 2,800,000
ACT
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition				Jul. 5, 2021
Percentage of equity interests acquired				100.00%
Fair value of the consideration transferred		1,306,214,000		$ 1,310,000,000
Business Combination, Consideration Transferred, Liabilities Incurred				36,500,000
Total revenue								386,800,000
Net Income								23,100,000
Amortization of Intangible Assets								7,000,000
Business Combination, Acquisition Related Costs								2,900,000
ACT | Cash paid for acquisition
Business Acquisition [Line Items]
Fair value of the consideration transferred				1,300,000,000
ACT | Equity transferred in acquisition
Business Acquisition [Line Items]
Fair value of the consideration transferred				$ 10,000,000
UTXL
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition					Jun. 1, 2021
Percentage of equity interests acquired					100.00%
Fair value of the consideration transferred		37,230,000			$ 37,200,000
UTXL | Cash paid for acquisition
Business Acquisition [Line Items]
Fair value of the consideration transferred					32,200,000
UTXL | Escrow For Sellers Indemnification Obligations [Member]
Business Acquisition [Line Items]
Fair value of the consideration transferred					2,250,000
UTXL | Contingent consideration (annual payment)
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current		2,500,000			2,500,000			2,500,000
Business Combination, Contingent Consideration, Liability, Noncurrent		2,500,000						2,500,000
UTXL | Contingent consideration (total payment)
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability					$ 5,000,000
Eleos
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition						Feb. 1, 2021
Percentage of equity interests acquired						79.44%
Fair value of the consideration transferred		41,518,000				$ 41,500,000
Eleos | Escrow For Sellers Indemnification Obligations [Member]
Business Acquisition [Line Items]
Fair value of the consideration transferred						$ 4,100,000
Warehousing Co
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition							Jan. 1, 2020
Percentage of equity interests acquired							100.00%
Fair value of the consideration transferred	[1]	66,444,000
Business Combination, Contingent Consideration, Liability							$ 18,300,000		16,200,000
Payment for Contingent Consideration Liability, Operating Activities								8,100,000	8,100,000
Contingent consideration associated with acquisition								6,700,000
Warehousing Co | Previously Reported [Member]
Business Acquisition [Line Items]
Fair value of the consideration transferred							66,900,000
Business Combination, Contingent Consideration, Liability							18,700,000
Warehousing Co | Restatement Adjustment [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability							400,000
Warehousing Co | Cash paid for acquisition
Business Acquisition [Line Items]
Fair value of the consideration transferred								48,200,000
Warehousing Co | Escrow For Sellers Indemnification Obligations [Member]
Business Acquisition [Line Items]
Fair value of the consideration transferred								6,800,000
Warehousing Co | Contingent consideration (annual payment)
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current		$ 8,100,000					8,100,000	$ 8,100,000	8,100,000
Business Combination, Contingent Consideration, Liability, Noncurrent									$ 8,100,000
Warehousing Co | Contingent consideration (total payment)
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability							$ 24,300,000
[1]	See above for a description of the working capital adjustments made to Warehousing Co.'s purchase price allocation during the measurement period.

Acquisitions - Tables (Details)

Acquisitions - Tables (Details) - USD ($) $ / shares in Units, $ in Thousands		Dec. 31, 2021	Dec. 06, 2021	Jul. 05, 2021	Jun. 01, 2021	Feb. 01, 2021	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue							$ 6,387,329	$ 5,374,934
Business Acquisition, Pro Forma Net Income (Loss)							$ 763,393	$ 437,835
Business Acquisition, Pro Forma Earnings Per Share, Diluted							$ 4.57	$ 2.57
Noncontrolling interest							$ (10,281)
Goodwill	[1]	$ 3,515,135					3,515,135	$ 2,922,964
Finite and Indefinite Lived Trade names		168,000					168,000
Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets		372,200					372,200
Employment Contracts
Business Acquisition [Line Items]
Finite-lived intangible assets		2,000					2,000
Computer Software, Intangible Asset
Business Acquisition [Line Items]
Finite-lived intangible assets		10,500					10,500
ACT
Business Acquisition [Line Items]
Fair value of the consideration transferred		1,306,214		$ 1,310,000
Cash and cash equivalents		17,477					17,477
Trade receivables		104,220					104,220
Prepaid expenses		15,803					15,803
Other current assets		3,537					3,537
Property and equipment		427,722					427,722
Operating lease right-of-use assets		4,053					4,053
Identifiable intangible assets 2	[2]	406,160					406,160
Other noncurrent assets		1,739					1,739
Total assets		980,711					980,711
Accounts payable		(19,386)					(19,386)
Accrued payroll and payroll-related expenses		(33,411)					(33,411)
Accrued liabilities		(9,302)					(9,302)
Claims accruals – current and noncurrent portions		(40,958)					(40,958)
Operating lease liabilities – current and noncurrent portions		(4,052)					(4,052)
Long-term debt – current and noncurrent portions		(54,024)					(54,024)
Deferred tax liabilities		0					0
Other long-term liabilities		(4,243)					(4,243)
Total liabilities		(165,376)					(165,376)
Noncontrolling interest		0
Total stockholders' equity		0					0
Goodwill		490,879					490,879
Trade name		148,100					148,100
ACT | Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets		250,800					250,800
ACT | Employment Contracts
Business Acquisition [Line Items]
Finite-lived intangible assets		800					800
ACT | Computer Software, Intangible Asset
Business Acquisition [Line Items]
Finite-lived intangible assets		6,500					6,500
UTXL
Business Acquisition [Line Items]
Fair value of the consideration transferred		37,230			$ 37,200
Cash and cash equivalents		8,206					8,206
Trade receivables		9,451					9,451
Prepaid expenses		0					0
Other current assets		0					0
Property and equipment		54					54
Operating lease right-of-use assets		0					0
Identifiable intangible assets 2	[2]	22,121					22,121
Other noncurrent assets		0					0
Total assets		39,832					39,832
Accounts payable		(14,183)					(14,183)
Accrued payroll and payroll-related expenses		(247)					(247)
Accrued liabilities		(69)					(69)
Claims accruals – current and noncurrent portions		(418)					(418)
Operating lease liabilities – current and noncurrent portions		0					0
Long-term debt – current and noncurrent portions		0					0
Deferred tax liabilities		0					0
Other long-term liabilities		0					0
Total liabilities		(14,917)					(14,917)
Noncontrolling interest		0
Total stockholders' equity		0					0
Goodwill		12,315					12,315
MME
Business Acquisition [Line Items]
Fair value of the consideration transferred		164,382	$ 164,400
Cash and cash equivalents		14,716					14,716
Trade receivables		21,915					21,915
Prepaid expenses		2,067					2,067
Other current assets		462					462
Property and equipment		49,192					49,192
Operating lease right-of-use assets		52,065					52,065
Identifiable intangible assets 2	[2]	52,960					52,960
Other noncurrent assets		139					139
Total assets		193,516					193,516
Accounts payable		(7,681)					(7,681)
Accrued payroll and payroll-related expenses		(7,106)					(7,106)
Accrued liabilities		(544)					(544)
Claims accruals – current and noncurrent portions		(1,090)					(1,090)
Operating lease liabilities – current and noncurrent portions		(46,375)					(46,375)
Long-term debt – current and noncurrent portions		0					0
Deferred tax liabilities		(19,009)					(19,009)
Other long-term liabilities		(568)					(568)
Total liabilities		(82,373)					(82,373)
Noncontrolling interest		0
Total stockholders' equity		0					0
Goodwill		53,239					53,239
Eleos
Business Acquisition [Line Items]
Fair value of the consideration transferred		41,518				$ 41,500
Cash and cash equivalents		2,237					2,237
Trade receivables		545					545
Prepaid expenses		47					47
Other current assets		0					0
Property and equipment		0					0
Operating lease right-of-use assets		560					560
Identifiable intangible assets 2	[2]	15,850					15,850
Other noncurrent assets		0					0
Total assets		19,239					19,239
Accounts payable		(156)					(156)
Accrued payroll and payroll-related expenses		(605)					(605)
Accrued liabilities		(1,391)					(1,391)
Claims accruals – current and noncurrent portions		0					0
Operating lease liabilities – current and noncurrent portions		(560)					(560)
Long-term debt – current and noncurrent portions		0					0
Deferred tax liabilities		0					0
Other long-term liabilities		(475)					(475)
Total liabilities		(3,187)					(3,187)
Noncontrolling interest		(10,281)
Total stockholders' equity		(10,281)					(10,281)
Goodwill		35,747					35,747
Warehousing Co
Business Acquisition [Line Items]
Fair value of the consideration transferred	[3]	66,444
Cash and cash equivalents	[3]	1,388					1,388
Trade receivables	[3]	3,301					3,301
Prepaid expenses	[3]	608					608
Other current assets	[3]	78					78
Property and equipment	[3]	1,938					1,938
Operating lease right-of-use assets	[3]	12,356					12,356
Identifiable intangible assets 2	[2],[3]	55,681					55,681
Other noncurrent assets	[3]	458					458
Total assets	[3]	75,808					75,808
Accounts payable	[3]	(347)					(347)
Accrued payroll and payroll-related expenses	[3]	0					0
Accrued liabilities	[3]	(644)					(644)
Claims accruals – current and noncurrent portions	[3]	0					0
Operating lease liabilities – current and noncurrent portions	[3]	(12,356)					(12,356)
Long-term debt – current and noncurrent portions	[3]	0					0
Deferred tax liabilities	[3]	0					0
Other long-term liabilities	[3]	0					0
Total liabilities	[3]	(13,347)					(13,347)
Noncontrolling interest	[3]	0
Total stockholders' equity	[3]	0					0
Goodwill	[3]	$ 3,983					$ 3,983
[1]	Except for the net accumulated amortization related to deferred tax assets in the Truckload segment, the net carrying amount and gross carrying amount are equal since there are no accumulated impairment losses.
[2]	Includes $372.2 million in customer relationships ($250.8 million attributed to ACT), $2.0 million in noncompete agreements ($0.8 million attributed to ACT), $10.5 million in internally developed software ($6.5 million attributable to ACT), and $168.0 million in trade names ($148.1 million attributed to ACT).
[3]	See above for a description of the working capital adjustments made to Warehousing Co.'s purchase price allocation during the measurement period.

Investments (Detail)

Investments (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2021USD ($)Securities	Dec. 31, 2020USD ($)Securities	Dec. 31, 2019USD ($)
Schedule of Restricted Investments [Line Items]
Cost or Amortized Cost	[1]	$ 5,866	$ 9,001
Gross Unrealized, Gains		0	2
Gross Unrealized, Temporary Losses		(7)	(8)
Restricted investments, held-to-maturity	[1]	$ 5,859	$ 8,995
Restricted held to maturity investments		1 year
Securities with unrealized losses for less than 12 months | Securities		11	16
Duration of securities in unrealized loss position		12 months	12 months
Impairment losses		$ 0	$ 0	$ 0
United States corporate securities
Schedule of Restricted Investments [Line Items]
Cost or Amortized Cost		5,866	9,001
Gross Unrealized, Gains		0	2
Gross Unrealized, Temporary Losses		(7)	(8)
Restricted investments, held-to-maturity		$ 5,859	$ 8,995
[1]	Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity.

Equity Investments (Investments

Equity Investments (Investments and commitments) (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Oct. 01, 2020
Transportation Resource Partners III [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	[1],[2],[3]	6.00%
Total TRP investment commitment		$ 245,000
Amounts Committed To Invest		15,000
Remaining Investment Commitment		1,692
TRP Investment Commitment, Due in Next Twelve Months		$ 1,700
Transportation Resource Partners IV [Member]
Schedule of Equity Method Investments [Line Items]
TRP ownership interest	[1],[4],[5]	4.20%
Total TRP investment commitment		$ 116,065
Amounts Committed To Invest		4,900
Remaining Investment Commitment		654
TRP Investment Commitment, Due in Next Twelve Months		100
TRP Investment Commitment, Due in Second and Third Year		100
TRP Investment Commitment, Due in Fourth and Fifth Year		500
TRP Investment Commitment, Due after Fifth Year		$ 0
Transportation Resource Partners, Colnvest Partners, (NTI) [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	[1],[2]	0.00%
Total TRP investment commitment		$ 120,000
Amounts Committed To Invest		10,000
Remaining Investment Commitment		$ 0
Transportation Resource Partners, CoInvest Partners, (QLS) [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	[1]	25.00%
Total TRP investment commitment		$ 39,000
Amounts Committed To Invest		9,735
Remaining Investment Commitment		$ 0
Transportation Resource Partners, CoInvest Partners, FFR I [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	[1],[2]	7.40%
Total TRP investment commitment		$ 66,555
Amounts Committed To Invest		4,950
Remaining Investment Commitment		$ 0
Transportation Resource Partners V
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	[1],[6]	16.60%
Total TRP investment commitment		$ 180,700
Amounts Committed To Invest		30,000
Remaining Investment Commitment		17,803
TRP Investment Commitment, Due in Next Twelve Months		7,200
TRP Investment Commitment, Due in Second and Third Year		7,200
TRP Investment Commitment, Due in Fourth and Fifth Year		900
TRP Investment Commitment, Due after Fifth Year		$ 2,500
Transportation Resource Partners, Coinvest Partners, V (PW)
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	[1],[2],[6]	13.30%
Total TRP investment commitment		$ 30,000
Amounts Committed To Invest		4,000
Remaining Investment Commitment		0
Holdings Co.
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage			21.00%
Investment in Holdings Co.			$ 39,600
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		$ 36,600
[1]	The Company's share of the results is included within "Other income, net" in the consolidated statements of comprehensive income.
[2]	The TRP III, TRP IV Coinvestments, TRP V, and TRP V Coinvest are unconsolidated majority interests. Management considered the criteria set forth in ASC 323, Investments – Equity Method and Joint Ventures , to establish the appropriate accounting treatment for these investments. This guidance requires the use of the equity method for recording investments in limited partnerships where the "so minor" interest is not met. As such, the investments are being accounted for under the equity method. Knight's ownership interest reflects its ultimate ownership of the portfolio companies underlying the TRP III, TRP IV Coinvestment NTI, TRP IV Coninvestment QLS, TRP IV Coinvestment FFR, TRP V, and TRP V Coninvest legal entities.
[3]	Management anticipates that $1.7 million will be due in 2022.
[4]	In accordance with ASC 321, Investments – Equity Securities
[5]	Management anticipates that the following amounts will be due: $0.1 million in 2022, $0.1 million from 2023 through 2024, $0.5 million in 2025, and none thereafter
[6]	Management anticipates that the following amounts will be due: $7.2 million in 2022, $7.2 million from 2023 through 2024, $0.9 million from 2025 through 2026, and $2.5 million thereafter.

Equity Investments (Embark) (De

Equity Investments (Embark) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Apr. 16, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Investments	$ 25,000
Equity Securities, FV-NI, Cost	54,467		$ 0
Debt and Equity Securities, Unrealized Gain (Loss)	$ 4,500
Embark
Schedule of Equity Method Investments [Line Items]
Investment Owned, Face Amount		$ 25,000

Equity Investments (Carrying Va

Equity Investments (Carrying Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2021		Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 75,769		$ 77,562
Equity Securities, FV-NI, Cost	54,467		0
Investments	130,236		77,562
Transportation Resource Partners III [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	801		217
Transportation Resource Partners IV [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	3	[1]	2,952
Transportation Resource Partners, Colnvest Partners, (NTI) [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	37		5,609
Transportation Resource Partners, CoInvest Partners, (QLS) [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	12,444		16,240
Transportation Resource Partners, CoInvest Partners, FFR I [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	6,761		4,905
Transportation Resource Partners V
Schedule of Equity Method Investments [Line Items]
Equity method investments	12,043		3,304
Transportation Resource Partners, Coinvest Partners, V (PW)
Schedule of Equity Method Investments [Line Items]
Equity method investments	4,859		4,000
Holdings Co.
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 38,821	[2]	$ 40,335
[1]	In accordance with ASC 321, Investments – Equity Securities
[2]	In accordance with ASC 323, Investments – Equity Method and Joint Ventures, the net investment balance includes accretion of amortization of certain definite-lived intangibles.

Trade Receivables, net (Schedul

Trade Receivables, net (Schedule Of Trade Receivables) (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable, gross		$ 932,999	$ 600,572
Less: Allowance for doubtful accounts		(21,663)	(22,093)
Trade receivables, net		911,336	578,479
Trade Customers [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable, gross		847,305	570,611
Equipment Manufacturers [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable, gross		11,923	5,680
Insurance Premiums
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable, gross	[1]	43,455	5,804
Other [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable, gross	[1]	$ 30,316	$ 18,477
[1]	Prior year amounts within the table above have been reclassified to conform to current year presentation.

Trade Receivables, net (Rollfor

Trade Receivables, net (Rollforward of the allowance for doubtful accounts for trade receivables) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 22,093
Ending balance	21,663		$ 22,093
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	22,093		18,178	$ 16,355
Provision	10,900		17,267	16,925
Write-offs directly against the reserve	(776)		(902)	(2,652)
Write-offs for revenue adjustments	(11,504)		(12,450)	(12,450)
Other	950	[1]	0	0
Ending balance	$ 21,663		$ 22,093	$ 18,178
[1]	Represents allowance for doubtful trade accounts receivables assumed in 2021 from the Company's acquisitions. See Note 4 for further details regarding these acquisitions.

Notes Receivable, net (Schedule

Notes Receivable, net (Schedule of Notes Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross notes receivable	$ 17,104	$ 10,325
Allowance for doubtful notes receivable	(496)	(602)
Total notes receivable, net of allowance	16,608	9,723
Current portion, net of allowance	1,848	2,846
Long-term portion	14,760	6,877
Investment Owned, at Cost	$ 10,000
Investment Interest Rate	12.00%
Independent Contractor Relationship [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross notes receivable	$ 5,969	7,291
Third Party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross notes receivable	10,141	0
Other Relationship [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross notes receivable	$ 994	$ 3,034
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable interest rate	5.10%
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable interest rate	15.00%

Assets Held for Sale (Narrative

Assets Held for Sale (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Long Lived Assets Held-for-sale [Line Items]
Period of time assets are expected to be sold, months	12 months
Assets held for sale	$ 8,166	$ 29,756
Gain on sale of property and equipment	74,799	9,706	$ 32,935
Impairments	299	5,335	3,486
Equipment [Member]
Long Lived Assets Held-for-sale [Line Items]
Assets held for sale	8,200	29,800
Gain on sale of property and equipment	74,800	9,700	32,900
Impairments	$ 300	$ 500	$ 400

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets Schedule of Goodwill (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill at beginning of period		$ 2,922,964	$ 2,918,992	$ 2,919,176
Amortization		(9)	(11)	(232)
Goodwill, Acquired During Period	[1]	592,180	3,983	48
Goodwill at end of period		3,515,135	2,922,964	2,918,992
Net Carrying Amount	[2]	3,515,135	2,922,964
Goodwill, Impairment Loss		0	0	$ 0
Corporate, Non-Segment [Member]
Goodwill [Line Items]
Net Carrying Amount	[2]	82,510	46,763
Trucking [Member] | Operating Segments
Goodwill [Line Items]
Net Carrying Amount	[2]	2,658,086	2,658,095
Logistics [Member] | Operating Segments
Goodwill [Line Items]
Net Carrying Amount	[2]	54,827	42,512
LTL | Operating Segments
Goodwill [Line Items]
Net Carrying Amount	[2]	544,118	0
Intermodal [Member] | Operating Segments
Goodwill [Line Items]
Net Carrying Amount	[2]	$ 175,594	$ 175,594
[1]	The goodwill associated with the ACT and MME acquisitions was allocated to the LTL segment. The goodwill associated with the UTXL acquisition was allocated to the Logistics segment. The goodwill associated with the Warehousing Co, and Eleos acquisitions was allocated to the non-reportable segments. See Note 4 regarding the amount attributed to adjustments to the opening balance sheets.
[2]	Except for the net accumulated amortization related to deferred tax assets in the Truckload segment, the net carrying amount and gross carrying amount are equal since there are no accumulated impairment losses.

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets (Schedule of Intangible Assets, net) (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Customer Relationships:
Gross carrying value	[1]	$ 1,227,630	$ 894,597
Accumulated amortization		(201,139)	(145,852)
Customer relationships, net		1,026,491	748,745
Trade Name:
Gross carrying value		804,558	640,500
Intangible assets, net		$ 1,831,049	$ 1,389,245
[1]	The major categories of the Company's definite-lived intangible assets include customer relationships, non-compete agreements, internally-developed software, trade names, and others. Identifiable intangible assets subject to amortization have been recorded at fair value. Intangible assets related to acquisitions other than the 2017 Merger are amortized over a weighted-average amortization period of 19.0 years. The Company's customer relationship intangible assets related to the 2017 Merger are being amortized over a weighted average amortization period of 19.9 years.

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets (Finite-lived Intangible Assets Amortization Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Finite-Lived Intangible Assets Amortization Expense [Line Items]
Amortization of Intangible Assets	$ 55,299	$ 45,895	$ 42,876
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	64,700
Finite-Lived Intangible Assets, Amortization Expense, Year Two	64,200
Finite-Lived Intangible Assets, Amortization Expense, Year Three	64,200
Finite-Lived Intangible Assets, Amortization Expense, Year Four	64,100
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 62,700
Amortization related to other intangible assets [Member]
Schedule of Finite-Lived Intangible Assets Amortization Expense [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	19 years
Amortization of Intangible Assets	$ 13,924	4,520	1,501
Intangible assets related to the 2017 Merger [Member]
Schedule of Finite-Lived Intangible Assets Amortization Expense [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	19 years 10 months 24 days
Amortization of Intangible Assets	$ 41,375	$ 41,375	$ 41,375

Accrued Payroll and Purchased_3

Accrued Payroll and Purchased Transportation (Details) - USD ($)		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent		3.00%
Employee compensation	[1]	$ 146,326,000	$ 114,835,000
Accrued purchased transportation		70,758,000	46,053,000
Accrued payroll and purchased transportation		217,084,000	160,888,000
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount		2,000
Defined Contribution Plan, Cost		16,200,000	13,600,000	$ 8,800,000
Matching contributions liability		$ 14,500,000	$ 12,800,000
MME
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent		6.00%
Minimum [Member]
Defined Contribution Plan Eligible Age for Employee		18 years
Maximum [Member]
Defined Contribution Plan Eligible Age for Employee		21 years
[1]	Accrued payroll includes accruals related to the various 401(k) plans the Company offers to its employees. Depending on the plan, employees must meet the minimum age requirement (18 – 21 years) and have completed ninety days or one year of service with the Company in order to qualify. Employees' rights to employer contributions are fully vested after three or five years from their date of employment. The plans offer discretionary matching contributions of the greater of 100% up to 3.0% or 6.0% of an employee's eligible compensation or $2,000. The Company's employee benefits expense for matching contributions related to the 401(k) plans was approximately $16.2 million, $13.6 million, and $8.8 million in 2021, 2020, and 2019, respectively. This expense was included in "Salaries, wages, and benefits" in the consolidated statements of comprehensive income. As of December 31, 2021 and 2020, the balance above in accrued payroll included $14.5 million and $12.8 million, respectively, in matching contributions for the 401(k) plans.

Claims Accruals (Details)

Claims Accruals (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	$ 417,321	$ 349,742
Less: current portion of claims accruals	(206,607)	(174,928)
Claims accruals – less current portion	210,714	174,814
Auto and collision liability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	263,091	231,875
Workers' compensation liability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	90,481	94,609
Third party carrier claims liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	31,524	40
Owner-operator claims liability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	6,285	7,112
Cargo damage liability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	5,409	2,494
Employee medical reserves [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Claims accruals	$ 20,531	$ 13,612

Claims Accruals (Self Insurance

Claims Accruals (Self Insurance) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Self Insurance Retention	$ 10
Excess coverage layer		$ 5
Excess of excess coverage layer		5
Cargo Insurance per truck or trailer	2
Cargo insurance per occurrence	15
Knight Transportation Company [Member]
Loss Contingencies [Line Items]
Insurance Aggregate Deductible Amount		2.5
Self Retention For Employee Medical Health	0.4
Swift Transportation Company [Member]
Loss Contingencies [Line Items]
Self Insurance Retention		10
Self Insurance Retention Workers Compensation Claims Per Occurrence	5
Self Retention For Employee Medical Health	0.5
ACT
Loss Contingencies [Line Items]
Self Insurance Retention	2
Insurance Aggregate Deductible Amount	5
Self Insurance Retention Workers Compensation Claims Per Occurrence	1
Self Retention For Employee Medical Health	1
Policy Period November 1, 2021 to October 31, 2022
Loss Contingencies [Line Items]
Self Insurance Aggregate Coverage	100
Policy Period November 1, 2020 to October 31, 2021
Loss Contingencies [Line Items]
Self Insurance Aggregate Coverage		100
Policy Period November 1, 2019 to October 31, 2020 [Member]
Loss Contingencies [Line Items]
Self Insurance Aggregate Coverage		130
Policy Period, March 1 2019 to March 1, 2020 [Member] | Knight Transportation Company [Member]
Loss Contingencies [Line Items]
Excess Personal Injury And Property Damage Liability Insurance	2
Policy Period, March 1, 2018 to March 1, 2019 [Member] | Knight Transportation Company [Member]
Loss Contingencies [Line Items]
Excess Personal Injury And Property Damage Liability Insurance	1
Minimum [Member] | Knight Transportation Company [Member]
Loss Contingencies [Line Items]
Self Insurance Retention		1
Maximum [Member] | Knight Transportation Company [Member]
Loss Contingencies [Line Items]
Self Insurance Retention		$ 3
Maximum [Member] | ACT
Loss Contingencies [Line Items]
Insurance Aggregate Deductible Amount	$ 10

Income Taxes (Income Tax Expens

Income Taxes (Income Tax Expense (Benefit) ) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current expense:
Federal	$ 140,258	$ 80,060	$ 50,703
State	42,319	19,153	16,616
Foreign	8,382	4,248	5,526
Current expense (benefit), Total	190,959	103,461	72,845
Deferred expense (benefit):
Federal	48,874	29,640	28,618
State	(10,369)	7,292	3,712
Foreign	1,423	9,283	(1,377)
Deferred expense (benefit), Total	39,928	46,215	30,953
Income tax expense	$ 230,887	$ 149,676	$ 103,798

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%
Computed expected tax expense	$ 204,673	$ 117,665	$ 86,935
State income taxes, net of federal income tax benefit	23,063	22,423	17,803
Other	3,151	9,588	(940)
Income tax expense	$ 230,887	$ 149,676	$ 103,798

Income Taxes (Components Of Net

Income Taxes (Components Of Net Deferred Tax Asset (Liability) ) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Claims accrual	$ 79,496	$ 81,426
Allowance for doubtful accounts	5,530	5,727
Amortization of stock options	8,192	7,712
Accrued liabilities	11,497	17,941
Operating Lease Liabilities	34,260	29,278
Other	20,562	10,687
Total deferred tax assets	159,537	152,771
Valuation allowance	0	0
Total deferred tax assets, net	159,537	152,771
Deferred tax liabilities:
Property and equipment, principally due to differences in depreciation	(635,877)	(586,349)
Prepaid taxes, licenses and permits deducted for tax purposes	(15,241)	(12,629)
Intangible assets	(338,191)	(334,618)
Operating Lease Right-of-Use Assets	(34,016)	(28,259)
Other	(11,089)	(6,857)
Deferred tax liabilities	(1,034,414)	(968,712)
Deferred income taxes	$ (874,877)	$ (815,941)

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at beginning of year	$ 2,950	$ 4,083	$ 7,423
Increases for tax positions taken prior to beginning of year	0	0	38
Decreases for tax positions taken prior to beginning of year	(1,215)	(1,133)	(3,378)
Unrecognized tax benefits at end of year	$ 1,735	$ 2,950	$ 4,083

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Tax Credit Carryforward [Line Items]
Valuation allowance	$ 0	$ 0
Cumulative Undistributed Earnings Of Foreign Subsidiaries	107,000
Foreign Earnings Repatriated	23,000
Decrease in Unrecognized Tax Benefits is Reasonably Possible	300
Income Tax Examination, Penalties and Interest Accrued	$ 100	$ 300
Minimum [Member]
Tax Credit Carryforward [Line Items]
Open Tax Year	2016
State and Local Jurisdiction [Member] | Minimum [Member]
Tax Credit Carryforward [Line Items]
Income Tax Examination, Year under Examination	2014
State and Local Jurisdiction [Member] | Maximum [Member]
Tax Credit Carryforward [Line Items]
Income Tax Examination, Year under Examination	2020

Accounts Receivable Securitiz_3

Accounts Receivable Securitization (Detail) - USD ($) $ in Thousands		Apr. 23, 2021	Jul. 11, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Accounts Receivable Securitization [Line Items]
Program Fees				$ 3,100	$ 3,500	$ 7,200
2021 RSA
Schedule of Accounts Receivable Securitization [Line Items]
Debt Instrument, Issuance 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
RSA Borrowing Base				400,000
Accounts receivable securitization	[4]			(279,000)
Letters of Credit Outstanding, Amount				(65,300)
Debt Instrument, Unused Borrowing Capacity, Amount				55,700
Debt Issuance Costs, Net				$ 500
Debt Instrument, Interest Rate During Period				0.90%
2018 RSA [Member]
Schedule of Accounts Receivable Securitization [Line Items]
Debt Instrument, Issuance Date			Jul. 11, 2018
Final maturity date			Jul. 9, 2021
Receivables Sales Agreement, Borrowing Capacity			$ 325,000
Accordion Option Accounts Receivable Securitization	[1]		$ 175,000
Unused commitment fee rate	[2]		20 to 40 basis points
Program fees on outstanding balances	[3],[5]		one month LIBOR + 80 to 100 basis points
RSA Borrowing Base					302,700
Accounts receivable securitization	[4]				(214,000)
Letters of Credit Outstanding, Amount					(67,281)
Debt Instrument, Unused Borrowing Capacity, Amount					21,419
Debt Issuance Costs, Current, Net					$ 100
Debt Instrument, Interest Rate During Period					1.00%
[1]	The accordion option increases the maximum borrowing capacity, subject to participation by the purchasers.
[2]	The 2021 RSA and 2018 RSA commitment fee rates 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 index for LIBOR.
[4]	As of December 31, 2021, outstanding borrowings are included in "Accounts receivable securitization – less current portion" in the consolidated balance sheets and are offset by $0.5 million of deferred loan costs. As of December 31, 2020, outstanding borrowings are included in "Accounts receivable securitization – current portion" in the consolidated balance sheets and are offset by $0.1 million of deferred loan costs. Interest accrued on the aggregate principal balance at a rate of 0.9% and 1.0%, as of December 31, 2021 and 2020, respectively.
[5]	Only the rate for the 2018 RSA program fee is subject to the Company's consolidated total net leverage ratio.

Debt And Financing (Details)

Debt And Financing (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Sep. 03, 2021	Jul. 06, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-Term Debt excluding Revolver and Other		$ 1,249,969			$ 298,907
Less: current portion of long-term debt					0
Long-term debt – less current portion		1,037,552			298,907
Revolving line of credit		260,000			210,000
Long-term debt		1,509,969			508,907
Finance Lease Liabilities and Long-term Debt, Current Portion
Debt Instrument [Line Items]
Less: current portion of long-term debt		(212,417)
2021 Term Loan A-1
Debt Instrument [Line Items]
Long-Term Debt excluding Revolver and Other	[1],[2]	199,676			0
Maximum borrowing capacity			$ 200,000
Final maturity date			Dec. 3, 2022
Interest rate base			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]
Interest rate margin	[3]		0.75%
2021 Term Loan A-1 | Maximum [Member]
Debt Instrument [Line Items]
Interest rate margin	[3]		1.38%
2021 Term Loan A-2
Debt Instrument [Line Items]
Long-Term Debt excluding Revolver and Other	[1],[2]	199,607			0
Maximum borrowing capacity			$ 200,000
Final maturity date			Sep. 3, 2024
Interest rate base			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]
Interest rate margin	[3]		0.75%
2021 Term Loan A-2 | Maximum [Member]
Debt Instrument [Line Items]
Interest rate margin	[3]		1.38%
2021 Term Loan A-3
Debt Instrument [Line Items]
Long-Term Debt excluding Revolver and Other	[1],[2]	798,352			0
Maximum borrowing capacity			$ 800,000
Final maturity date			Sep. 3, 2026
Interest rate base			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]
Interest rate margin	[3]		0.88%
2021 Term Loan A-3 | Maximum [Member]
Debt Instrument [Line Items]
Interest rate margin	[3]		1.50%
2017 Term Loan
Debt Instrument [Line Items]
Long-Term Debt excluding Revolver and Other	[1],[4]	0			298,907
2021 Prudential Notes
Debt Instrument [Line Items]
Long-Term Debt excluding Revolver and Other	[1]	47,265			0
Debt Instrument, Unused Borrowing Capacity, Amount		77,600
2021 Prudential Notes | Minimum [Member]
Debt Instrument [Line Items]
Interest rate margin			4.05%
2021 Prudential Notes | Maximum [Member]
Debt Instrument [Line Items]
Interest rate margin			4.40%
Other Debt
Debt Instrument [Line Items]
Secured Debt, Other		5,069			0
2021 Revolver
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		$ 64,000
Maximum borrowing capacity	[5]		$ 1,100,000
Final maturity date			Sep. 3, 2026
Interest rate base	[5]		BSBY
Minimum principal payment — amount	[5]		$ 0
Minimum principal payment — frequency	[5]		Once
Minimum principal payment — commencement date	[5]		Sep. 3, 2026
Debt Instrument, Interest Rate During Period		1.064%
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]
Interest rate margin	[3],[5]		0.88%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.07%
2021 Revolver | Maximum [Member]
Debt Instrument [Line Items]
Interest rate margin	[3],[5]		1.50%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.20%
2017 Revolver
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount					29,300
2021 Term Loans
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period		1.022%
July 2021 Term Loan
Debt Instrument [Line Items]
Interest rate base				BSBY
Interest rate margin				1.00%
Line of Credit [Member] | 2021 Revolver
Debt Instrument [Line Items]
Revolving line of credit	[1],[6]	$ 260,000			0
Line of Credit [Member] | 2017 Revolver
Debt Instrument [Line Items]
Revolving line of credit	[1],[7]	0			210,000
Loans Payable [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 2,300,000
Loans Payable [Member] | 2021 Term Loan A-1
Debt Instrument [Line Items]
Debt Issuance Costs, Current, Net		300
Loans Payable [Member] | 2021 Term Loan A-2
Debt Instrument [Line Items]
Debt Issuance Costs, Net		400
Loans Payable [Member] | 2021 Term Loan A-3
Debt Instrument [Line Items]
Debt Issuance Costs, Net		$ 1,600
Loans Payable [Member] | 2017 Term Loan
Debt Instrument [Line Items]
Debt Issuance Costs, Current, Net					$ 1,100
Loans Payable [Member] | 2021 Prudential Notes
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 125,000
Loans Payable [Member] | July 2021 Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 1,200,000
[1]	Refer to Note 23 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 $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively.
[3]	The interest rate margin for the 2021 Term Loan and 2021 Revolver is based on the Company's consolidated leverage ratio. As of December 31, 2021, interest accrued at 1.022% on the 2021 Term Loans and 1.064% on the 2021 Revolver.
[4]	Net of $1.1 million in deferred loan costs at December 31, 2020.
[5]	The commitment fee for the unused portion of the 2021 Revolver is based on the Company's consolidated leverage ratio, and ranges from 0.07% to 0.20%. As of December 31, 2021, commitment fees on the unused portion of the 2021 Revolver accrued at 0.100% and outstanding letter of credit fees accrued at 1.000%.
[6]	The Company also had outstanding letters of credit of $64.0 million under the 2021 Revolver, primarily related to workers' compensation and self-insurance liabilities, at December 31, 2021.
[7]	The Company also had outstanding letters of credit of $29.3 million under the 2017 Revolver, primarily related to workers' compensation and self-insurance liabilities, at December 31, 2020.

Leases (Lease Cost) (Detail)

Leases (Lease Cost) (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease costs		$ 46,795	$ 80,456
Short-term lease cost ¹	[1]	8,426	6,544
Sublease income		(60)	(360)
Rental expense		55,161	86,640	$ 122,738
Amortization of property and equipment		37,659	16,638
Interest expense		5,232	2,896
Total finance lease cost		42,891	19,534
Total operating and finance lease costs		$ 98,052	$ 106,174
[1]	Short-term lease cost includes leases with a term of twelve months or less, as well as month-to-month leases and variable lease costs.

Leases (Lease Liability Calcula

Leases (Lease Liability Calculation Assumptions) (Details)	Dec. 31, 2021	Dec. 31, 2020
Revenue Equipment [Member]
Property, Plant and Equipment [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	1 year 7 months 6 days	2 years
Finance Lease, Weighted Average Remaining Lease Term	4 years	3 years 7 months 6 days
Operating Lease, Weighted Average Discount Rate, Percent	2.30%	2.40%
Finance Lease, Weighted Average Discount Rate, Percent	1.90%	2.40%
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	12 years 7 months 6 days	10 years 7 months 6 days
Operating Lease, Weighted Average Discount Rate, Percent	3.00%	3.70%

Leases (Maturity Analysis of Le

Leases (Maturity Analysis of Lease Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2022	$ 38,871
2023	27,124
2024	15,084
2025	11,037
2026	8,793
Thereafter	71,007
Future minimum lease payments	171,916
Less: amounts representing interest	(28,980)
Present value of minimum lease payments	142,936
Operating lease liabilities – current portion	(35,322)	$ (47,496)
Operating lease liabilities – less current portion	107,614	69,852
Finance Lease, Liability, Payment, Due [Abstract]
2022	54,741
2023	49,275
2024	91,115
2025	70,543
2026	9,839
Thereafter	45,185
Future minimum lease payments	320,698
Less: amounts representing interest	(14,526)
Present value of minimum lease payments	306,172
Finance lease liabilities – less current portion	$ 256,166	$ 138,243
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Finance lease liabilities and long-term debt – current portion

Leases (Supplemental Cash Flow)

Leases (Supplemental Cash Flow) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating cash flows for operating leases	$ 48,171	$ 83,675
Operating cash flows for finance leases	5,232	2,896
Financing cash flows for finance leases	$ 108,186	$ 83,910

Leases (Operating Lease Revenue

Leases (Operating Lease Revenue and Rental Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Gross property and equipment		$ 5,118,897	$ 4,223,348
Less: accumulated depreciation and amortization		(1,563,533)	(1,230,696)
Operating lease revenue		95,934	45,698
Variable lease revenue		1,353	1,691
Revenue Equipment [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment		103,200	103,100
Less: accumulated depreciation and amortization		(40,000)	(29,700)
Depreciation		20,600	20,600
Total lease revenue 1	[1]	97,287	47,389
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Operating lease revenue	[2]	$ 10,375	$ 10,365
[1]	Represents operating revenue earned by the Company for leasing equipment to independent contractors and other third-parties.
[2]	Represents non-operating income earned from leasing real estate to third parties.

Leases (Maturity Analysis of Fu

Leases (Maturity Analysis of Future Lease Revenues) (Details) $ in Thousands	Dec. 31, 2021USD ($)
Leases [Abstract]
2022	$ 38,262
2023	26,211
2024	12,492
2025	5,215
2026	1,926
Thereafter	3,618
Future minimum lease revenues	$ 87,724

Defined Benefit Pension Plan (D

Defined Benefit Pension Plan (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Retirement Benefits [Abstract]
Projected benefit obligation	$ 71,440
Total pension plan assets	70,467
Unfunded status	973
Accrued pension liability recognized 1	973	[1]
Amount Recorded in Other Comprehensive Income (Loss)	600
Net periodic pension income	1,483
Benefits paid	$ 2,981
Discount Rate (Point in Time)	2.53%
Discount Rate (Period of Time)	2.55%
Expected long-term rate of return on pension plan assets	6.00%
Contributions During the Period	$ 0
Defined Benefit Plan, Expected Loss, Next Fiscal Year	0
2022	3,594
2023	3,708
2024	3,854
2025	3,956
2026	4,043
2027 through 2030	20,543
Defined Benefit Plan, Expected Future Benefit Payments, Total	$ 39,698
[1]	The pension liability is included in "Other long-term liabilities" in the consolidated balance sheets.

Defined Benefit Pension Plan _2

Defined Benefit Pension Plan (Details)	Dec. 31, 2021
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan Assets, Actual Allocation	100.00%
Plan Assets, Target Allocation	100.00%
Defined Benefit Plan, Equity Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan Assets, Actual Allocation	30.00%
Plan Assets, Target Allocation	30.00%
Defined Benefit Plan, Debt Security
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan Assets, Actual Allocation	68.00%
Plan Assets, Target Allocation	70.00%
Defined Benefit Plan, Cash and Cash Equivalents
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan Assets, Actual Allocation	2.00%

Purchase Commitments (Details)

Purchase Commitments (Details) $ in Millions	Dec. 31, 2021USD ($)
Capital Addition Purchase Commitments Total Revenue Equipment [Member]
Long-term Purchase Commitment [Line Items]
Purchase Obligation, Due in Next Twelve Months	$ 858
Purchase Obligation, Due in Second and Third Year	58.6
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, Due in Next Twelve Months	585.8
Purchase Obligation, Due in Second and Third Year	50.4
Non revenue equipment purchase commitments [Member]
Long-term Purchase Commitment [Line Items]
Purchase Obligation, Due in Next Twelve Months	53.4
Purchase Obligation, Due in Second and Third Year	4.5
Purchase Obligation, Due in Fourth and Fifth Year	1.2
Purchase Obligation, Due after Fifth Year	$ 0

Contingencies and Legal Proce_4

Contingencies and Legal Proceedings (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Accrued legal		$ 18.1	$ 20.2
Accrual for Environmental Loss Contingencies, Gross		$ 1.1
CRST Expedited [Member] | Employee Compensation and Pay Practices Matters [Member]
Loss Contingencies [Line Items]
Loss Contingency, Allegations		The plaintiff alleges tortious interference with contract and unjust enrichment related to non-competition agreements entered into with certain of its drivers.
Loss Contingency, Name of Plaintiff		CRST Expedited, Inc.
Loss Contingency, Name of Defendant		Swift Transportation Co. of Arizona LLC.
Loss Contingency, Lawsuit Filing Date		March 20, 2017
Loss Contingency, Domicile of Litigation		United States District Court for the Northern District of Iowa
Loss Contingency, Opinion of Counsel		In July 2019, a jury issued an adverse verdict in this lawsuit. The court issued a decision granting in part and denying in part certain motions related to the jury’s verdict. Both parties have appealed the court’s decision. On August 6, 2021 a three-judge panel of the 8th Circuit Court of Appeals issued an opinion reversing the trial court’s decision. On October 4, 2021 the 8th Circuit Court of Appeals denied a petition for rehearing. The likelihood that a loss has been incurred is no longer probable, and the accrual for this lawsuit has accordingly been reversed as of December 31, 2021.
California Wage, Meal, and Rest Class Action [Member] | Employee Compensation and Pay Practices Matters [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 December 31, 2021.
California Wage, Meal, and Rest Class Action [Member] | Employee Compensation and Pay Practices Matters [Member] | California Wage, Meal, and Rest Class Action 1 [Member]
Loss Contingencies [Line Items]
Loss Contingency, Name of Plaintiff	[1]	John Burnell 1
Loss Contingency, Name of Defendant		Swift Transportation Co., Inc
Loss Contingency, Lawsuit Filing Date		March 22, 2010
Loss Contingency, Domicile of Litigation		United States District Court for the Central District of California
California Wage, Meal, and Rest Class Action [Member] | Employee Compensation and Pay Practices Matters [Member] | California Wage, Meal, and Rest Class Action 2 [Member]
Loss Contingencies [Line Items]
Loss Contingency, Name of Plaintiff	[1]	James R. Rudsell 1
Loss Contingency, Name of Defendant		Swift Transportation Co. of Arizona, LLC and Swift Transportation Company
Loss Contingency, Lawsuit Filing Date		April 5, 2012
Loss Contingency, Domicile of Litigation		United States District Court for the Central District of California
Ninth circuit owner operator misclassification class action 1 [Member] | Independent-Contractor Matters [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 FLSA 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 Plaintiff	[1]	Joseph Sheer, Virginia Van Dusen, Jose Motolinia, Vickii Schwalm, Peter Wood 1
Loss Contingency, Name of Defendant		Swift Transportation Co., Inc., Interstate Equipment Leasing, Inc., Jerry Moyes, and Chad Killebrew
Loss Contingency, Lawsuit Filing Date		December 22, 2009
Loss Contingency, Domicile of Litigation		Unites 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 December 31, 2021, 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 (Details

Share Repurchase Plans (Details) - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Nov. 24, 2020	May 30, 2019	Jun. 01, 2018
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Value		$ 57,175	$ 179,585	$ 86,892
Common Stock [Member]
Class of Stock [Line Items]
Company shares repurchased, shares		1,377	4,841
Knight-Swift Repurchase Plan, June 1, 2018 [Member]
Class of Stock [Line Items]
Amount remaining							$ 200
Knight-Swift Share Repurchase Plan, May 31, 2019 [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 250,000
Amount remaining						$ 54,100
Stock Repurchased and Retired During Period, Value		$ 0	$ 179,585
Knight-Swift Share Repurchase Plan, May 31, 2019 [Member] | Common Stock [Member]
Class of Stock [Line Items]
Company shares repurchased, shares		0	4,841
Knight-Swift Share Repurchase Plan, November 30, 2020
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount	[1]				$ 250,000
Amount remaining		$ 192,800	$ 250,000
Stock Repurchased and Retired During Period, Value	[1]	$ 57,175	$ 0
Knight-Swift Share Repurchase Plan, November 30, 2020 | Common Stock [Member]
Class of Stock [Line Items]
Company shares repurchased, shares	[1]	1,377	0
[1]	$192.8 million and $250.0 million remained available under the 2020 Knight-Swift Share Repurchase Plan as of December 31, 2021 and December 31, 2020, respectively.

Share Repurchase Plan (Subseque

Share Repurchase Plan (Subsequent Event) (Details) - USD ($) $ in Thousands, shares in Millions	Feb. 22, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Value		$ 57,175	$ 179,585	$ 86,892
Subsequent Event [Member]
Class of Stock [Line Items]
Company shares repurchased, shares	0.7
Stock Repurchased and Retired During Period, Value	$ 36,900
Amount remaining	$ 155,900

Stock-based Compensation (Stock

Stock-based Compensation (Stock-based Compensation Expense) (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 28,131	$ 26,594	$ 16,038
Income tax benefit	[1]	8,357	4,949	3,344
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		232	567	1,149
Restricted Stock Units Excluding Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		18,190	13,496	9,734
Performance Shares Excluding Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		15,073	5,576	2,492
Equity Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		33,495	19,639	13,375
Liability Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	[2]	$ (5,364)	$ 6,955	$ 2,663
[1]	The income tax benefit is calculated by applying the statutory tax rate to stock-based compensation expense for equity awards, as the expense associated with liability awards is not tax deductible.
[2]	Includes awards granted to executive management in November 2019 that, per the original agreement, would ultimately settle in cash upon fulfilling a requisite service period (for restricted stock units) and fulfilling a requisite service period and achieving performance targets (for performance units). During 2021, the Company amended the agreements for outstanding awards to ultimately settle in shares after each requisite service period.

Stock-based Compensation (Compe

Stock-based Compensation (Compensation Costs Not Yet Recognized) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 64,010
Weighted Average Period	2 years 3 months 18 days
Restricted Stock Units Excluding Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 49,704
Weighted Average Period	2 years 2 months 12 days
Performance Shares Excluding Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 14,306
Weighted Average Period	2 years 4 months 24 days

Stock-based Compensation (Sto_2

Stock-based Compensation (Stock Awards Granted) (Details) - shares		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		674,711	868,535	772,522
Restricted Stock Units Excluding Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		562,021	722,499	588,819
Performance Shares Excluding Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		112,690	146,036	102,776
Equity Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		674,711	868,535	691,595
Liability Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	[1],[2]	0	0	80,927
Performance units (liability) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted				48,556
Restricted Stock Units Liability [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted				32,371
[1]	Includes 32,371 restricted stock units in 2019.
[2]	Includes 48,556 performance units in 2019.

Stock-based Compensation (Summa

Stock-based Compensation (Summary Of Activity Related To Stock Options) (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares Under Option
Granted		674,711	868,535	772,522
Exercised		(207,242)	(382,254)	(443,288)
Aggregate Intrinsic Value
Share Price		$ 60.94	$ 41.82
Share-based Payment Arrangement, Option [Member]
Shares Under Option
Stock options outstanding		302,976
Granted		0
Exercised		(207,242)
Expired		(7,419)
Forfeited		(3,308)
Stock options outstanding		85,007	302,976
Aggregate number of stock options expected to vest at a future date		0
Exercisable		85,007
Weighted Average Exercise Price
Stock options outstanding		$ 29.45
Granted		0
Exercised		28.59
Expired		23.80
Forfeited		33.35
Stock options outstanding		31.95	$ 29.45
Aggregate number of stock options expected to vest at a future date		0
Exercisable		$ 31.95
Weighted Average Remaining Contractual Term
Stock options outstanding		7 months 6 days	1 year 2 months 12 days
Aggregate number of stock options expected to vest at a future date		0 years
Exercisable		7 months 6 days
Aggregate Intrinsic Value
Stock options outstanding	[1]	$ 3,748
Stock options outstanding	[1]	2,464	$ 3,748
Aggregate number of stock options expected to vest at a future date	[1]	0
Exercisable	[1]	$ 2,464
[1]	The aggregate intrinsic value was computed using the closing share price on December 31, 2021 of $60.94 and on December 31, 2020 of $41.82, as applicable.

Stock-based Compensation (Sum_2

Stock-based Compensation (Summary Of Exercise Of Stock Options) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Number of stock options exercised	207,242	382,254	443,288
Intrinsic value of stock options exercised	$ 4,120	$ 4,929	$ 5,183
Cash received upon exercise of stock options	5,924	10,199	10,478
Income tax benefit	$ 1,304	$ 1,029	$ 221

Stock-based Compensation (Statu

Stock-based Compensation (Status of Nonvested Stock Options) (Details) - Share-based Payment Arrangement, Option [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares
Nonvested	86,779
Vested	(83,707)
Forfeited	(3,072)
Nonvested	0
Weighted Average Fair Value
Nonvested	$ 6.78
Vested	6.78
Forfeited	6.78
Nonvested	$ 0
Total fair value of shares vested	$ 0.6	$ 1	$ 1.5

Stock-based Compensation (Rollf

Stock-based Compensation (Rollforward of Nonvested Restricted Stock Awards) (Details) - $ / shares		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares
Granted		674,711	868,535	772,522
RSUs and restricted stock
Shares
Nonvested		1,723,838
Granted		562,021
Vested	[1]	(456,670)
Forfeited		(119,428)
Nonvested		1,709,761	1,723,838
Shares withheld for taxes		170,280
Weighted Average Fair Value
Nonvested	[2]	$ 34.07
Granted	[2]	50.63
Vested	[2]	32.53
Forfeited	[2]	39.97
Nonvested	[2]	$ 39.81	$ 34.07
Restricted Stock Units Liability [Member]
Shares
Granted				32,371
Vested	[1]	(18,697)
[1]	Includes 170,280 shares withheld for taxes and 18,697 net units settled in cash which were excluded from the "Common stock issued to employees" activity within the consolidated statements of stockholders' equity.
[2]	The fair value of each restricted stock unit is based on the closing market price on the grant date.

Stock-based Compensation (Rol_2

Stock-based Compensation (Rollforward of Nonvested Performance Shares) (Details) - $ / shares		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019
Shares
Granted		674,711		868,535	772,522
Performance units
Shares
Nonvested		549,730
Granted		112,690
Shares earned above target		45,409
Vested	[1]	136,225
Nonvested		571,604	[2]	549,730
Shares withheld for taxes		63,815
Weighted Average Fair Value
Nonvested		$ 39.50
Granted		60.55
Shares earned above target		37.89
Vested		45.02
Nonvested		$ 44.22		$ 39.50
Performance units (liability) [Member]
Shares
Granted					48,556
Vested		39,225
[1]	Includes 63,815 shares withheld for taxes and 39,225 net units settled in cash which were excluded from the "Common stock issued to employees" activity within the consolidated statements of stockholders' equity.
[2]	The performance measurement period for performance units granted in 2018 is January 1, 2019 to December 31, 2021 (three full calendar years). The performance measurement period for performance units granted in 2019 is January 1, 2020 to December 31, 2022 (three full calendar years). The performance measurement period for performance units granted in 2020 is January 1, 2021 to December 31, 2023 (three full calendar years). The performance measurement period for units granted in 2021 is January 1, 2022 to December 31, 2024 (three full calendar years). All performance units will vest one month following the expiration of the performance measurement period.

Stock-based Compensation (Perfo

Stock-based Compensation (Performance unit fair value assumptions) (Details) - Performance units - $ / shares		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	[1]	0.67%	0.78%	0.66%
Expected volatility	[2]	36.00%	37.99%	34.88%
Average peer volatility	[2]	35.49%	35.62%	27.96%
Average peer correlation coefficient	[3]	60.00%	59.00%	60.00%
Risk-free rate of return	[4]	0.92%	0.20%	1.60%
Expected term (in years)	[5]	3 years 1 month 6 days	3 years 1 month 6 days	3 years 1 month 6 days
Weighted-average fair value of performance units granted		$ 60.55	$ 42.41	$ 37.24
[1]	The dividend yield, used to project stock price to the end of the performance period, is based on the Company's historical experience and future expectation of dividend payouts. Total stockholder return is determined assuming that dividends are reinvested in the issuing entity over the performance period, which is mathematically equivalent to utilizing a 0% dividend yield.
[2]	Management (or peer company) estimated volatility using the Company's (or peer company's) historical share price performance over the remaining performance period as of the grant date.
[3]	The correlation coefficients are used to model the way in which each entity tends to move in relation to each other; the correlation assumptions were developed using the same stock price data as the volatility assumptions.
[4]	The risk-free interest rate assumption is based on US Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the performance award.
[5]	Since the Monte Carlo Simulation valuation is an open form model that uses an expected life commensurate with the performance period, the expected life of the performance units was assumed to be the period from the grant date to the end of the performance period.

Stock-based Compensation (Narra

Stock-based Compensation (Narrative) (Detail)	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum purchasing power of common stock for an employee during offering period | $	$ 6,250
Maximum purchasing power of common stock for an employee during a calendar year | $	$ 25,000
Maximum percent of total voting power or value of all classes of common stock which restricts from participation of ESPP	5.00%
2012 ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares remaining available	1,000,000
Number of shares authorized for issuance	1,400,000
Employment period for eligibility of employees participation	90 days
Percentage of payroll deductions from employees compensation	15.00%
Percentage of fair market value of the purchase price	95.00%
Number of shares purchased by the employees	63,000
Weighted-average fair value of the shares purchased | $ / shares	$ 44.12
Common Stock [Member] | 2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares remaining available	4,700,000

Weighted Average Shares Outst_3

Weighted Average Shares Outstanding (Calculation Of Basic And Diluted Earnings Per Share Attributable To Stockholders) (Detail) - shares shares in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Basic weighted average common shares outstanding		165,860	169,711	171,541
Dilutive effect of equity awards		1,200	838	601
Diluted weighted average common shares outstanding		167,060	170,549	172,142
Anti-dilutive shares excluded from diluted earnings per share	[1]	208	63	603
[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.

Fair Value Measurement (Estimat

Fair Value Measurement (Estimated Fair Values) (Detail) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Financial Assets:
Cost or Amortized Cost	[1]	$ 5,866	$ 9,001
Restricted investments, held-to-maturity	[1]	5,859	8,995
Equity method investments		75,769	77,562
Equity Method Investments (Estimated Fair Value)		75,769	77,562
Investments in equity securities		74,201	18,675
Convertible note		10,141	0
Financial Liabilities:
Long-term Debt		1,509,969	508,907
Accounts receivable securitization, Carrying Value		278,483	0
Revolving line of credit		260,000	210,000
Business Combination, Contingent Consideration, Liability		13,100	16,200
2021 Term Loan A-1 | Loans Payable [Member]
Financial Liabilities:
Debt Issuance Costs, Current, Net		300
2021 Term Loan A-1
Financial Liabilities:
Long-term Debt	[2]	199,676	0
Term loan, Fair Value	[2]	200,000	0
2021 Term Loan A-2
Financial Liabilities:
Long-term Debt	[2]	199,607	0
Term loan, Fair Value	[2]	200,000	0
2021 Term Loan A-3
Financial Liabilities:
Long-term Debt	[2]	798,352	0
Term loan, Fair Value	[2]	800,000	0
2021 Revolver
Financial Liabilities:
Revolving line of credit		260,000	0
2021 Prudential Notes
Financial Liabilities:
Long-term Debt	[3]	47,265	0
Term loan, Fair Value	[3]	47,354	0
Debt Instrument, Fair Value Disclosure			2,400
2021 RSA
Financial Liabilities:
Accounts receivable securitization, Carrying Value	[4]	278,483	0
Debt Instrument, Fair Value Disclosure	[4]	279,000	0
Debt Issuance Costs, Net		500
2017 Term Loan
Financial Liabilities:
Long-term Debt	[5]	0	298,907
Term loan, Fair Value	[5]	0	300,000
Debt Issuance Costs, Net			1,100
2017 Revolver
Financial Liabilities:
Revolving line of credit		0	210,000
2018 RSA [Member]
Financial Liabilities:
Accounts receivable securitization, Carrying Value	[6]	0	213,918
Debt Instrument, Fair Value Disclosure	[6]	$ 0	214,000
Debt Issuance Costs, Current, Net			$ 100
[1]	Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity.
[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 $0.3 million, $0.4 million, and $1.6 million in deferred loan costs as of December 31, 2021, respectively.
[3]	The carrying amount of the 2021 Prudential Notes is net of $0.1 million in deferred loan costs and $2.4 million in fair value adjustments as of December 31, 2021 .
[4]	The carrying amount of the 2021 RSA is net of $0.5 million in deferred loan costs as of December 31, 2021.
[5]	The carrying amount of the 2017 Term Loan is net of $1.1 million in deferred loan costs as of December 31, 2020
[6]	The carrying amount of the 2018 RSA is net of $0.1 million in deferred loan costs as of December 31, 2020.

Fair Value Measurement - Recurr

Fair Value Measurement - Recurring and Nonrecurring Measurements (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020
Assets, Fair Value Disclosure [Abstract]
Convertible note		$ 10,141		$ 0
Gain (Loss) on Investments		100
Debt and Equity Securities, Unrealized Gain (Loss)		4,500
Total pension plan assets		70,467
Liabilities, Fair Value Disclosure [Abstract]
Business Combination, Contingent Consideration, Liability		13,100		16,200
Equipment [Member]
Assets, Fair Value Disclosure [Abstract]
Total Losses, Equipment				(5,300)
Fair Value, Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Convertible note	[1]	10,141
Gain (Loss) on Investments	[2]	141
Assets, Fair Value Disclosure		74,201	[3]	18,675	[4]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		14,456	[3]	3,553	[4]
Debt and Equity Securities, Gain (Loss)		16,400
Debt and Equity Securities, Unrealized Gain (Loss)		10,900		3,700
Debt and Equity Securities, Realized Gain (Loss)		5,500
Total pension plan assets		70,467
Liabilities, Fair Value Disclosure [Abstract]
Business Combination, Contingent Consideration, Liability		13,100	[5]	16,200	[6]
Contingent Consideration Gain (Loss)		0	[5]	(6,730)	[6]
Fair Value, Recurring [Member] | Defined Benefit Plan, Equity Securities, US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		14,877
Fair Value, Recurring [Member] | Defined Benefit Plan, Equity Securities, Non-US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		6,304
Fair Value, Recurring [Member] | Fixed Income Securities
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		47,873
Fair Value, Recurring [Member] | Defined Benefit Plan, Cash
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		1,413
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs
Assets, Fair Value Disclosure [Abstract]
Convertible note	[1]	0
Assets, Fair Value Disclosure		74,201	[3]	18,675	[4]
Total pension plan assets		70,467
Liabilities, Fair Value Disclosure [Abstract]
Business Combination, Contingent Consideration, Liability		0	[5]	0	[6]
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs | Defined Benefit Plan, Equity Securities, US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		14,877
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs | Defined Benefit Plan, Equity Securities, Non-US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		6,304
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs | Fixed Income Securities
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		47,873
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs | Defined Benefit Plan, Cash
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		1,413
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member]
Assets, Fair Value Disclosure [Abstract]
Convertible note	[1]	0
Assets, Fair Value Disclosure		0	[3]	0	[4]
Total pension plan assets		0
Liabilities, Fair Value Disclosure [Abstract]
Business Combination, Contingent Consideration, Liability		0	[5]	0	[6]
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member] | Defined Benefit Plan, Equity Securities, US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member] | Defined Benefit Plan, Equity Securities, Non-US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member] | Fixed Income Securities
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member] | Defined Benefit Plan, Cash
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member]
Assets, Fair Value Disclosure [Abstract]
Convertible note	[1]	10,141
Assets, Fair Value Disclosure		0	[3]	0	[4]
Total pension plan assets		0
Liabilities, Fair Value Disclosure [Abstract]
Business Combination, Contingent Consideration, Liability		13,100	[5]	16,200	[6]
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member] | Defined Benefit Plan, Equity Securities, US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member] | Defined Benefit Plan, Equity Securities, Non-US
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member] | Fixed Income Securities
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member] | Defined Benefit Plan, Cash
Assets, Fair Value Disclosure [Abstract]
Total pension plan assets		0
Fair Value, Nonrecurring [Member]
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0		0
Fair Value, Nonrecurring [Member] | Equipment [Member]
Assets, Fair Value Disclosure [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		0	[7]	5,851	[8]
Total Losses, Equipment		(299)	[7]	(5,335)	[8]
Fair Value, Nonrecurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs | Equipment [Member]
Assets, Fair Value Disclosure [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		0	[7]	0	[8]
Fair Value, Nonrecurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member] | Equipment [Member]
Assets, Fair Value Disclosure [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		0	[7]	5,851	[8]
Fair Value, Nonrecurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member] | Equipment [Member]
Assets, Fair Value Disclosure [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		$ 0	[7]	$ 0	[8]
[1]	Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity.
[2]	The Company recognized $0.1 million of unrealized gains on the convertible note during 2021, which is included within "Other income, net" within the consolidated statements of comprehensive income. 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.
[3]	Fair value activity from the investments in equity securities is recorded in "Other income, net" within the consolidated statements of comprehensive income. During 2021, the Company recognized $16.4 million in gains on these investments in equity securities, consisting of $10.9 million in unrealized gains and $5.5 million in realized gains.
[4]	Fair value activity from the investments in equity securities is recorded in "Other income, net" within the consolidated statements of comprehensive income. During 2020, the Company recognized $3.7 million in unrealized gains on these investments in equity securities.
[5]	The Company did not recognize any gains (losses) during 2021 related to the revaluation of these liabilities. Refer to Note 4 for information regarding the components of these liabilities.
[6]	During the fourth quarter of 2020, the Company increased the estimated fair value of the remaining contingent consideration representing the final two annual payments, resulting in a $6.7 million fair value adjustment of the deferred earnout, which was recorded in “Miscellaneous operating expenses” in the consolidated statement of comprehensive income.
[7]	Reflects the non-cash impairment of certain revenue equipment held for sale (within the non-reportable segments and the Truckload segment).
[8]	Reflects the non-cash impairment of certain alternative fuel technology (within the non-reportable segments) and certain revenue equipment held for sale (within the Truckload segment). The Company recognized $5.3 million of impairments during 2020.

Related Party Transactions (Sch

Related Party Transactions (Schedule Of Services Received And Provided By Company) (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current		$ 14	$ 135
Accounts Payable, Related Parties, Current		44	51
Central Freight Lines, Inc. [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current		0	133
Accounts Payable, Related Parties, Current		0	0
DPF Mobile [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current		0	0
Accounts Payable, Related Parties, Current		0	41
Other Affiliated Entities [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current		14	2
Accounts Payable, Related Parties, Current		44	10
Freight Services [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift		0	7,893	$ 19,996
Received by Knight-Swift		0	0	0
Freight Services [Member] | Central Freight Lines, Inc. [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	7,837	19,651
Received by Knight-Swift	[1]	0	0	0
Freight Services [Member] | SME Industries [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	56	345
Received by Knight-Swift	[1]	0	0	0
Facility and Equipment Leases [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift		0	59	340
Received by Knight-Swift		311	506	369
Facility and Equipment Leases [Member] | Central Freight Lines, Inc. [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	48	322
Received by Knight-Swift	[1]	0	277	369
Facility and Equipment Leases [Member] | Other Affiliated Entities [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	11	18
Received by Knight-Swift	[1]	311	229	0
Other Services [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift		31	442	1,873
Received by Knight-Swift		35	68	2,652
Other Services [Member] | Central Freight Lines, Inc. [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	427	1,834
Received by Knight-Swift	[1]	0	0	0
Other Services [Member] | DPF Mobile [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	0	0	0
Received by Knight-Swift	[1]	0	33	220
Other Services [Member] | Other Affiliated Entities [Member]
Related Party Transaction [Line Items]
Provided by Knight-Swift	[1]	31	15	39
Received by Knight-Swift	[1]	$ 35	$ 35	$ 2,432
[1]	Entities affiliated with former Board member Jerry Moyes include Central Freight Lines, SME Industries, and DPF Mobile. "Other 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. • Freight Services Provided by Knight-Swift — The Company charges each of these companies for transportation services. • Freight Services Received by Knight-Swift — Transportation services received from Central Freight represent less-than-truckload freight services rendered to haul parts and equipment to Company shop locations. • Other Services Provided by Knight-Swift — Other services provided by the Company to the identified related parties include equipment sales and miscellaneous services. • Other Services Received by Knight-Swift — Consulting fees, diesel particulate filter cleaning, sales of various parts and tractor accessories, and certain third-party payroll and employee benefits administration services from the identified related parties are included in other services received by the Company. During the quarter ended September 30, 2020, the ownership percentage of Jerry Moyes and related affiliates fell below the threshold requiring related party disclosure. The amounts included in this Note 24 pertain to transactions that occurred prior to the date that the ownership percentage changed.

Information by Segment, Geogr_3

Information by Segment, Geography, and Customer Concentration (Segment Descriptions) (Details)	12 Months Ended
	Dec. 31, 2021Segment
Segment Reporting Information [Line Items]
Number of Reportable Segments	4
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Segment Reporting, Description of All Other Segments	The non-reportable segments include five operating segments that consist of support services provided to the Company's customers and independent contractors (including repair and maintenance shop services, equipment leasing, warranty services, and insurance), trailer parts manufacturing, warehousing, and certain driving academy activities, as well as certain corporate expenses (such as legal settlements and accruals, certain impairments, and amortization of intangibles related to the 2017 Merger and various acquisitions).
Trucking [Member] | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information, Description of Products and Services	The Truckload reportable segment is comprised of nine full truckload operating segments that provide similar transportation services to the Company's customers utilizing similar transportation equipment over both irregular (one-way movement) and/or dedicated routes. The Truckload reportable segment consists of irregular route and dedicated, refrigerated, expedited, flatbed, and cross-border operations.
Logistics [Member] | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information, Description of Products and Services	The Logistics reportable segment is comprised of six logistics operating segments that provide similar transportation services to the Company's customers and primarily consist of brokerage and other freight management services utilizing third-party transportation providers and their equipment.
LTL | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information, Description of Products and Services	Our LTL segment, established in 2021 through the ACT and MME acquisitions, is comprised of two operating segments and provides our customers with regional LTL transportation services through a network of approximately 100 service centers in the Company's geographical footprint. The Company's LTL service also includes national coverage to customers by utilizing partner carriers for areas outside of the Company's direct network.
Intermodal [Member] | Operating Segments
Segment Reporting Information [Line Items]
Segment Reporting Information, Description of Products and Services	The Intermodal reportable segment is comprised of two intermodal operating segments that provide similar transportation services to the Company's customers. These transportation services include arranging the movement of customers' freight through third-party intermodal rail services on the Company’s trailing equipment (containers and trailers on flat cars), as well as drayage services to transport loads between the railheads and customer locations.

Information by Segment (Summary

Information by Segment (Summary Of Financial Information By Segments) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total revenue	$ 5,998,019	$ 4,673,863	$ 4,843,950
Percentage of Revenue	100.00%	100.00%	100.00%
Operating income (loss)	$ 965,697	$ 564,438	$ 427,438
Percentage Of Operating Income	100.00%	100.00%	100.00%
Depreciation and amortization of property and equipment	$ 522,596	$ 460,775	$ 420,082
Percentage Of Depreciation	100.00%	100.00%	100.00%
Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 5,770,183	$ 4,553,333	$ 4,761,320
Percentage of Revenue	96.20%	97.40%	98.30%
Operating income (loss)	$ 951,585	$ 597,814	$ 495,119
Percentage Of Operating Income	98.50%	105.90%	115.90%
Depreciation and amortization of property and equipment	$ 464,104	$ 405,623	$ 369,504
Percentage Of Depreciation	88.90%	88.00%	88.00%
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 306,414	$ 188,882	$ 130,782
Percentage of Revenue	5.10%	4.00%	2.70%
Operating income (loss)	$ 14,112	$ (33,376)	$ (67,681)
Percentage Of Operating Income	1.50%	(5.90%)	(15.90%)
Depreciation and amortization of property and equipment	$ 58,492	$ 55,152	$ 50,578
Percentage Of Depreciation	11.10%	12.00%	12.00%
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenue	$ (78,578)	$ (68,352)	$ (48,152)
Percentage of Revenue	(1.30%)	(1.40%)	(1.00%)
Trucking [Member] | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 4,098,005	$ 3,786,030	$ 3,952,866
Percentage of Revenue	68.30%	81.00%	81.60%
Operating income (loss)	$ 784,436	$ 578,512	$ 468,749
Percentage Of Operating Income	81.20%	102.50%	109.70%
Depreciation and amortization of property and equipment	$ 422,558	$ 390,417	$ 355,270
Percentage Of Depreciation	80.90%	84.70%	84.60%
Logistics [Member] | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 817,003	$ 375,841	$ 352,988
Percentage of Revenue	13.60%	8.00%	7.30%
Operating income (loss)	$ 93,920	$ 20,245	$ 21,869
Percentage Of Operating Income	9.70%	3.60%	5.10%
Depreciation and amortization of property and equipment	$ 1,357	$ 829	$ 728
Percentage Of Depreciation	0.30%	0.20%	0.20%
LTL | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 396,308	$ 0	$ 0
Percentage of Revenue	6.60%	0.00%	0.00%
Operating income (loss)	$ 31,169	$ 0	$ 0
Percentage Of Operating Income	3.20%	0.00%	0.00%
Depreciation and amortization of property and equipment	$ 24,844	$ 0	$ 0
Percentage Of Depreciation	4.80%	0.00%	0.00%
Intermodal [Member] | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 458,867	$ 391,462	$ 455,466
Percentage of Revenue	7.70%	8.40%	9.40%
Operating income (loss)	$ 42,060	$ (943)	$ 4,501
Percentage Of Operating Income	4.40%	(0.20%)	1.10%
Depreciation and amortization of property and equipment	$ 15,345	$ 14,377	$ 13,506
Percentage Of Depreciation	2.90%	3.10%	3.20%

Information by Geography (Narra

Information by Geography (Narrative) (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting [Abstract]
Percentage of foreign operations total revenue	5.00%	5.00%	5.00%
Long lived assets of foreign operations	5.00%	5.00%

Information by Segment, Geogr_4

Information by Segment, Geography, and Customer Concentration Information by Customer Concentration (Details) - Revenue Benchmark [Member] - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue, Major Customer [Line Items]
Concentration Risk, Threshold Percentage	10.00%	10.00%	10.00%
Major Customer And Its Subsidiaries [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	16.10%	16.80%	13.30%