Knight Transportation 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 25, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	Knight Transportation Inc
Document Type	10-K
Current Fiscal Year End Date	-19
Entity Common Stock, Shares Outstanding		81,986,743
Entity Public Float			$1,500,000,000
Amendment Flag	FALSE
Entity Central Index Key	929452
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets:
Cash and cash equivalents	$17,066	$992
Trade receivables, net of allowance for doubtful accounts of $3,355 and $2,409, respectively	143,531	116,391
Notes receivable, net of allowance for doubtful notes receivable of $351 and $312, respectively	1,020	774
Related party notes and interest receivable		748
Prepaid expenses	17,423	15,026
Assets held for sale	23,248	16,476
Other current assets	13,345	11,066
Income tax receivable	19,432
Current deferred tax assets	3,187	3,359
Total current assets	238,252	164,832
Property and Equipment:
Revenue equipment	803,410	683,275
Land and land improvements	52,531	45,615
Buildings and building improvements	125,492	115,201
Furniture and fixtures	17,322	18,605
Shop and service equipment	16,653	9,564
Leasehold improvements	3,037	3,382
	1,018,445	875,642
Less: accumulated depreciation and amortization	-266,399	-283,851
Property and equipment, net	752,046	591,791
Notes receivable, long-term	4,065	4,047
Goodwill	47,067	10,257
Intangible assets, net	3,575	0
Other long-term assets and restricted cash and investments	37,280	36,194
Total long-term assets	844,033	642,289
Total assets	1,082,285	807,121
Current Liabilities:
Accounts payable	19,122	14,354
Accrued payroll and purchased transportation	34,127	13,864
Accrued liabilities	20,604	19,062	[1]
Claims accrual – current portion	18,532	15,616
Dividend payable – current portion	200	168
Total current liabilities	92,585	63,064
Long-term Liabilities:
Claims accrual – long-term portion	11,505	8,889
Long-term dividend payable and other liabilities	2,513	2,486
Deferred tax liabilities	162,007	140,149
Long-term debt	134,400	38,000
Total long-term liabilities	310,425	189,524
Total liabilities	403,010	252,588
Commitments and Contingencies (Note 5)
Shareholders' Equity:
Preferred stock, $0.01 par value; 50,000 shares authorized; none issued	0	0
Common stock, $0.01 par value; 300,000 shares authorized; 81,842 and 80,199 shares issued and outstanding at December 31, 2014 and 2013, respectively	818	802
Additional paid-in capital	185,184	150,858
Accumulated other comprehensive income	12,231	4,582
Retained earnings	479,527	397,346
Total Knight Transportation shareholders' equity	677,760	553,588
Noncontrolling interest	1,515	945
Total shareholders' equity	679,275	554,533
Total liabilities and shareholders' equity	$1,082,285	$807,121
[1]	Income tax payable is included in Accrued Liabilities of our consolidated balance sheets.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified
Allowance for doubtful accounts (in Dollars)	$3,355	$2,409
Allowance for doubtful notes receivable (in Dollars)	$351	$312
Prеfеrrеd stock, par valuе (in Dollars per share)	$0.01	$0.01
Prеfеrrеd stock, sharеs authorizеd	50,000	50,000
Prеfеrrеd stock, issuеd	0	0
Common stock, par value (in Dollars per share)	$0.01	$0.01
Common stock, shares authorized	300,000	300,000
Common stock, shares issued	81,842	80,199
Common stock, shares outstanding	81,842	80,199

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Revenue, before fuel surcharge	$925,985	$791,851	$752,151
Fuel surcharge	176,347	177,386	183,885
Total revenue	1,102,332	969,237	936,036
Operating Expenses:
Salaries, wages and benefits	271,815	234,306	238,266
Fuel	203,758	214,843	230,178
Operations and maintenance	71,558	64,715	61,875
Insurance and claims	31,133	29,350	32,138
Operating taxes and licenses	17,972	15,624	16,184
Communications	4,899	5,015	5,172
Depreciation and amortization	92,893	86,129	85,056
Purchased transportation	238,041	189,667	148,022
Miscellaneous operating expenses	7,541	15,679	10,878
Total operating expenses	939,610	855,328	827,769
Income from operations	162,722	113,909	108,267
Other Income (Expense):
Interest income	458	413	417
Interest expense	-730	-462	-457
Other income	9,380	2,844	1,550
Total other income	9,108	2,795	1,510
Income before income taxes	171,830	116,704	109,777
Income Taxes	67,809	46,680	45,014
Net income	104,021	70,024	64,763
Net income attributable to noncontrolling interest	-1,159	-742	-646
Net income attributable to Knight Transportation	$102,862	$69,282	$64,117
Basic Earnings Per Share (in Dollars per share)	$1.27	$0.87	$0.80
Diluted Earnings Per Share (in Dollars per share)	$1.25	$0.86	$0.80
Weighted Average Shares Outstanding - Basic (in Shares)	80,947	79,994	79,673
Weighted Average Shares Outstanding - Diluted (in Shares)	82,042	80,330	80,000

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Net income	$104,021		$70,024		$64,763
Other comprehensive income, net of tax:
Realized gains from available-for-sale securities reclassified to net income (1)	-1,932	[1]	-1,189	[1]	-38	[1]
Unrealized gains from changes in fair value of available-for-sale securities (2)	9,581	[2]	6,073	[2]	184	[2]
Comprehensive income	111,670		74,908		64,909
Comprehensive income attributable to non controlling interest	-1,159		-742		-646
Comprehensive income attributable to Knight Transportation	$110,511		$74,166		$64,263
[1]	Net of current income taxes of $1,233, $736, and $23, respectively.
[2]	Net of deferred income taxes of $6,203, $3,758, and $111, respectively.

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parentheticals) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net of current income taxes	$1,233	$736	$23
Net of deferred income taxes	$6,203	$3,758	$111

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity (USD $)	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
In Thousands, except Share data
Balance at Dec. 31, 2011	$794	$133,502	$344,604	($448)	$478,452	$391	$478,843
Balance (in Shares) at Dec. 31, 2011	79,392,000
Exercise of stock options and RSUs	4	3,619			3,623		3,623
Exercise of stock options and RSUs (in Shares)	359,000						281,993
Issuance of common stock		148			148		148
Issuance of common stock (in Shares)	9,000
Shares withheld from RSU settlement			-650		-650		-650
Excess tax benefit of stock option exercises		30			30		30
Employee stock-based compensation expense		6,317			6,317		6,317
Cash dividends paid and dividends accrued			-59,858		-59,858		-59,858
Net income attributable to Knight			64,117		64,117		64,117
Other comprehensive income				146	146		146
Distribution to noncontrolling interest						-429	-429
Net income attributable to noncontrolling interest						646	646
Balance at Dec. 31, 2012	798	143,616	348,213	-302	492,325	608	492,933
Balance (in Shares) at Dec. 31, 2012	79,760,000
Exercise of stock options and RSUs	4	4,341			4,345		4,345
Exercise of stock options and RSUs (in Shares)	429,000						345,302
Issuance of common stock		167			167		167
Issuance of common stock (in Shares)	10,000
Shares withheld from RSU settlement			-739		-739		-739
Excess tax benefit of stock option exercises		-81			-81		-81
Employee stock-based compensation expense		2,815			2,815		2,815
Cash dividends paid and dividends accrued			-19,410		-19,410		-19,410
Net income attributable to Knight			69,282		69,282		69,282
Other comprehensive income				4,884	4,884		4,884
Distribution to noncontrolling interest						-405	-405
Net income attributable to noncontrolling interest						742	742
Balance at Dec. 31, 2013	802	150,858	397,346	4,582	553,588	945	554,533
Balance (in Shares) at Dec. 31, 2013	80,199,000
Exercise of stock options and RSUs	16	24,350			24,366		24,366
Exercise of stock options and RSUs (in Shares)	1,634,000						1,551,400
Issuance of common stock		200			200		200
Issuance of common stock (in Shares)	9,000
Shares withheld from RSU settlement			-1,027		-1,027		-1,027
Excess tax benefit of stock option exercises		5,273			5,273		5,273
Employee stock-based compensation expense		4,503			4,503		4,503
Cash dividends paid and dividends accrued			-19,654		-19,654		-19,654
Net income attributable to Knight			102,862		102,862		102,862
Other comprehensive income				7,649	7,649		7,649
Distribution to noncontrolling interest						-589	-589
Net income attributable to noncontrolling interest						1,159	1,159
Balance at Dec. 31, 2014	$818	$185,184	$479,527	$12,231	$677,760	$1,515	$679,275
Balance (in Shares) at Dec. 31, 2014	81,842,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows From Operating Activities:
Net income	$104,021	$70,024	$64,763
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	92,893	86,129	85,056
Gain on sale of equipment	-16,840	-7,550	-8,916
Earn-out on sold investment		-467	-216
Gain on sale of available-for-sale securities	-3,165	-1,925	-61
Income from investment in Transportation Resource Partners III	-6,139	-669	-261
Impairment of investment in Transportation Resource Partners	1,041	209
Compensation expense for issuance of common stock to certain members of board of directors	200	167	148
Provision for allowance for doubtful accounts and notes receivable	1,351	1,008	883
Deferred income taxes	17,060	-5,338	-1,975
Excess tax benefits related to stock-based compensation	-5,273		-30
Stock-based compensation expense	4,503	2,815	6,317
Changes in operating assets and liabilities:
Trade receivables	-17,031	-14,828	-2,167
Other current assets	-1,872	1,384	-2,844
Prepaid expenses	-1,647	2,008	-6,904
Income tax receivable	-19,432		3,821
Other long-term assets	442	-390	81
Accounts payable	4,285	2,424	4,783
Accrued liabilities and claims accrual	22,790	3,517	8,342
Net cash provided by operating activities	177,187	138,518	150,820
Cash Flows From Investing Activities:
Purchases of property and equipment	-260,389	-140,612	-160,633
Proceeds from sale of equipment/assets held for sale	81,555	55,244	39,789
Purchase of long-term available-for-sale securities		-10,035	-2,033
Cash proceeds from sale of available-for-sale securities	6,355	8,782	112
Cash receipt from notes receivable	2,309	2,383	1,856
Cash payment for notes receivable		-646	-366
Cash proceeds from related party notes receivable	748	1,570	54
Investment in Barr-Nunn Transportation	-110,517
Cash payments to Transportation Resource Partners	-129	-3,201	-2,382
Cash proceeds from Transportation Resource Partners	12,814	467	216
Change in restricted cash and investments	339	343	-416
Net cash used in investing activities	-266,915	-85,705	-123,803
Cash Flows From Financing Activities:
Dividends paid	-19,648	-19,445	-59,141
Excess tax benefits related to stock-based compensation	5,273		30
Proceeds from (payments of) borrowing on line of credit	96,400	-42,000	25,000
Cash distribution to noncontrolling interest holder	-589	-405	-429
Proceeds from exercise of stock options	24,366	4,345	3,623
Net cash provided by (used in) financing activities	105,802	-57,505	-30,917
Net increase (decrease) in Cash and Cash Equivalents	16,074	-4,692	-3,900
Cash and Cash Equivalents, beginning of year	992	5,684	9,584
Cash and Cash Equivalents, end of year	17,066	992	5,684
Non-cash investing and financing transactions:
Equipment acquired included in accounts payable	25	2,892	2,206
Dividend accrued for restricted stock units	2,220	2,216	2,251
Transfer from property and equipment to assets held for sale	56,521	40,422	34,244
Financing provided to independent contractors for equipment sold	1,579	1,731	1,200
Cash flow information:
Income taxes paid	68,020	51,904	40,422
Interest expense paid	$666	$450	$475

Note_1_Organization_and_Summar

Note 1 - Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	1.      Organization and Summary of Significant Accounting Policies and Revision of Prior Period Reported Amounts
	a.             Nature of Business
	Knight Transportation, Inc. (an Arizona corporation) and subsidiaries (the "Company") is a truckload carrier of general commodities and transportation logistics services provider headquartered in Phoenix, Arizona. The Company also has service centers located throughout the United States. The Company has two reportable segments, Trucking and Logistics. The Trucking segment provides truckload carrier dry van, temperature-controlled (refrigerated), and drayage services, and the Logistics segment provides logistics, freight management, brokerage, rail intermodal, and other non-trucking services. The Company is subject to regulation by the U.S. Department of Transportation, U.S. Environmental Protection Agency, U.S. Department of Homeland Security, and various state regulatory authorities.
	b.             Significant Accounting Policies
	Principles of Consolidation - The accompanying consolidated financial statements include Knight Transportation, Inc. and its wholly owned and controlled subsidiaries. The Company's non-controlling interests in subsidiaries are not significant. All intercompany accounts and transactions are eliminated upon consolidation.
	Use of Estimates - The preparation of financial statements in conformity with United States Generally Accepted Accounting Principles ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements. Estimates and assumptions equally apply to the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Cash and Cash Equivalents - Cash and cash equivalents are comprised of cash, money market funds, and short-term, 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.
	Notes Receivable – The Company provides financing to independent contractors and third parties on equipment sold or leased under the Company's equipment sale program. Most of the notes are collateralized and are due in weekly installments, including principal and interest payments, ranging from 2% to 20%. The Company had 109 and 117 loans outstanding from independent contractors and third parties as of December 31, 2014 and 2013, respectively.
	The notes receivable balances are classified separately between current and long-term notes in the consolidated balance sheets. The current and long-term balances of our notes receivables as of December 31, 2014 and 2013 are as follows:
			2014			2013
			(In thousands)
	Notes receivable from independent contractors		$	1,554		$	503
	Notes receivable from third parties			3,882			4,630
	Gross notes receivable			5,436			5,133
	Allowance for doubtful notes receivable			(351	)		(312	)
	Total notes receivable, net of allowance		$	5,085		$	4,821
	Current portion, net of allowance			1,020			774
	Long-term portion		$	4,065		$	4,047
	Assets Held for Sale - The Company had $23.2 million and $16.5 million of revenue equipment not being utilized in operations, which is classified as assets held for sale, as of December 31, 2014 and 2013, respectively. Assets held for sale are recorded at the lower of depreciated value or fair market value less selling costs and are not subject to depreciation. The Company periodically reviews the carrying value of these assets for possible impairment. No impairment was recorded in 2014 or 2013. The Company expects to sell these assets within 12 months.
	Other Current Assets - Included in other current assets are inventories of tires, spare parts, and fuel.
	Property and Equipment - Property and equipment is stated at cost less accumulated depreciation. Property and equipment is depreciated to estimated salvage values using the straight-line method of depreciation over the following estimated useful lives:
		Years
	Land improvements	5	-	10
	Buildings and improvements	10	-	30
	Furniture and fixtures	3	-	10
	Shop and service equipment	2	-	10
	Revenue equipment	5	-	10
	Leasehold improvements	1	-	5
	The Company expenses repairs and maintenance as incurred. For the years ended December 31, 2014, 2013, and 2012, repairs and maintenance expense totaled approximately $30.9 million, $30.5 million, and $30.4 million, respectively. The expense is included in “Operations and maintenance” expense in the accompanying consolidated statements of income.
	The Company periodically reviews the reasonableness of its estimates regarding useful lives and salvage values for revenue equipment and other long-lived assets based upon, among other things, the Company's experience with similar assets, conditions in the used revenue equipment market, and prevailing industry practice.
	Tires on revenue equipment purchased are capitalized as a part of the equipment cost and depreciated over the life of the vehicle. Replacement tires and recapping costs are expensed when placed in service.
	Other Long-term Assets and Restricted Cash and Investments include:
			2014			2013
			(In thousands)
	Investment in Transportation Resource Partners (TRP)		$	477		$	2,035
	Investment in Transportation Resource Partners III (TRP III)			5,412			11,440
	Restricted Cash and Investments			3,264			3,603
	Available-For-Sale Equity Securities			26,884			17,454
	Other			1,243			1,662
			$	37,280		$	36,194
	In 2003, the Company signed a partnership agreement with TRP, a company that makes privately negotiated equity investments.  According to the original partnership agreement, the Company committed to invest $5.0 million out of approximately $260.0 million total, for a 1.9% ownership interest. In early 2006, the Company increased the commitment amount to $5.5 million.  Contributions to TRP are accounted for using the cost method as the level of influence over the operations of TRP is minor. In 2014, the Company received distributions totaling $2.1 million from TRP for the sale of TRP portfolio companies. The proceeds from the sale resulted a $1.6 million gain for the Company, with the remaining proceeds representing a return of investment in TRP. The Company also received additional earn-outs of $467,000 and $216,000 in 2013 and 2012, respectively, for disposed portfolios. The earn-outs are recognized as gains in the year received. The Company also recorded impairment of $1.0 million and $209,000 in 2014 and 2013, respectively, for an other-than-temporary loss on the investments remaining within the TRP portfolio. No impairment was recorded in 2012. No contributions have been made to TRP since 2011. The Company's ownership interest in TRP is approximately 1.9%, with a carrying value of $477,000 and $2.0 million at December 31, 2014 and 2013, respectively.
	In the fourth quarter of 2008, the Company committed to invest $15.0 million in a new partnership managed and operated by the managers and principals of TRP. The new partnership, TRP III, focuses on the same investment opportunities as TRP. Since its inception, the Company has contributed approximately $10.9 million to TRP III, leaving an outstanding commitment of $4.1 million as of December 31, 2014. The investment in TRP III is accounted for using the equity method. The Company has recorded income of approximately $6.1 million, $669,000, and $261,000 for its investment in TRP III for years ended December 31, 2014, 2013, and 2012, respectively. In 2014, the Company received distributions totaling $12.3 million from TRP III for the sale of TRP III portfolio companies. At December 31, 2014, the investment balance in TRP III was $5.4 million, compared to $11.4 million at December 31, 2013.  The Company's ownership interest was approximately 6.1% as at December 31, 2014.
	Restricted Cash and Investments – In connection with the Company's self-insurance program, $3.3 million and $3.6 million have been set aside in escrow accounts to meet statutory requirements as of December 31, 2014 and 2013, respectively.
	In accordance with the provisions of ASC 210, Balance Sheet, and ASC 320, Investments – Debt and Equity Securities, the Company's investments in debt or equity securities are classified as either trading securities, held-to-maturity securities, or available-for-sale securities, based on the Company's intent with respect to those securities. Investments in debt and equity securities are classified as trading securities if they are held principally for the purpose of selling in the near term. Investments in debt securities are classified as held-to-maturity if the Company has the positive intent to hold such securities to maturity and the ability to do so. Investments in debt and equity securities not classified as trading or held-to-maturity are classified as available-for-sale.
	Impairment of Long-Lived Assets – ASC 360-10, Property, Plant and Equipment, provides a single accounting model for the assessment of impairment of long-lived assets. In accordance with ASC 360-10, Long-lived Assets, such as property and equipment and purchased intangibles to be held and used in operations, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Long-lived assets are grouped at the lowest level at which identifiable cash flows are largely independent when assessing impairment. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets classified as held for sale are not depreciated and are presented in the Company's consolidated balance sheets at the lower of the carrying amount or fair value less costs to sell. Revenue equipment classified as held for sale is presented in "Assets held for sale" on the Company's consolidated balance sheets. Recoverability of long-lived assets is dependent upon, among other things, the Company's ability to continue to achieve profitability in order to meet its obligations when they become due. In the opinion of management, based upon current information, the carrying amount of long-lived assets will be recovered by future cash flows generated through the use of such assets over their respective estimated useful lives.
	Goodwill & Intangibles, net - Goodwill is not amortized, but it is reviewed for impairment at least annually or more frequently should any of the circumstances listed in ASC 350-20, Goodwill, occur. The standard permits an entity to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step impairment test is unnecessary. However, if an entity concludes otherwise, then it is required to perform the impairment test as prescribed in ASC 350-20. Goodwill is required to be tested for impairment at the reporting unit level utilizing a two-step methodology. The initial step requires the Company to determine the fair value of the reporting unit and compare it to the carrying value of such unit, including goodwill. No impairment is recognized if the fair value exceeds the carrying value; however, if the carrying value of the reporting unit exceeds its fair value, the goodwill of the reporting unit may be impaired. The amount, if any, of the impairment would then be measured in the second step. In 2014, the Company changed the date of the annual impairment testing to September 30, from December 31. This change did not result in the delay, acceleration or avoidance of an impairment charge. The Company believes this change in accounting principle is preferable because it better aligns with the Company’s annual strategic and planning process and alleviates administrative burden during the year-end reporting period. This change to the annual goodwill impairment testing was applied prospectively and had no effect on the consolidated financial statements. This change was not applied retrospectively as it is impractical to do so because retrospective application would have required the application of significant estimates and assumptions without use of hindsight. The Company completed this annual test as of both December 31, 2013, and September 30, 2014, and no adjustment for impairment was determined to be necessary. The Company has no accumulated goodwill impairment loss from prior years.
	In conjunction with the acquisition of Roads West in 2006, the basis of goodwill for tax purposes was determined to be in excess of the book basis of goodwill. Under this circumstance, ASC 740, Income Taxes, requires that the goodwill be separated into two components for the acquisitions before the adoption of ASC 805, Business Combination. The first component is equivalent to book goodwill, and future tax amortization of this component is treated as a temporary difference, for which a deferred tax liability is established. The second component is the excess tax goodwill over the book goodwill, for which no deferred taxes are recognized. The tax benefit from the recognition of the amortization of the second component on the tax return is treated as a reduction in the book basis of goodwill. The finite lived intangible portion was amortized using the straight-line method over a five-year period, and was fully amortized as of December 31, 2011.
	The changes in the carrying amounts of goodwill were as follows:
			2014			2013
			(In thousands)
	Goodwill at beginning of period		$	10,257		$	10,276
	Acquisition			36,835			-
	Amortization relating to deferred tax assets			(25	)		(19	)
	Goodwill at end of period		$	47,067		$	10,257
	In conjunction with the acquisition of Barr-Nunn Transportation, Inc. and certain affiliates (“Barr-Nunn”), identifiable intangible assets subject to amortization were recorded at fair value at the acquisition date totaling $3.7 million, and is being amortized over a weighted average amortization period of 7.6 years. Amortization expense associated with these intangible assets from the date of acquisition to December 31, 2014 was $0.1 million and was included in depreciation and amortization in the consolidated statement of income. Future amortization expense for intangible assets is estimated at $0.5 million for 2015 through 2019. The balance of intangible assets in the consolidated balance sheet is $3.6 million at December 31, 2014. The Company did not have any intangible assets subject to amortization as of December 31, 2013.
	Claims Accrual - The claims reserves represent accruals for estimated pending claims within the self-insured retention ("SIR"), including adverse development of known claims and incurred but not reported claims. These estimates are based on the Company's claims experience, including claims settlement patterns, historical payment trends, the experience/knowledge of the Company's self-administered claims as well as that of the third-party administrator as it relates to workers' compensation claims, along with assumptions about future events. The most significant assumptions used in the estimation process include determining the trend in costs, the expected cost of claims incurred but not reported, and the expected costs to settle or pay outstanding claims. Changes in assumptions and changes in actual experience could cause these estimates to change significantly in the near term. A higher SIR may cause assumptions and estimates to vary more unpredictably than a lower SIR.
	Revenue Recognition - The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable, and collectability is probable. These conditions are met upon delivery.
	In accordance with ASC 605-45, Revenue Recognition – Principal Agent Consideration, the Company accounts for revenue from our Trucking operations, our Logistics operations, and revenue on freight transported by independent contractors on a gross basis. The Company is the primary obligor in the arrangements, the Company has the ability to establish prices, the Company has discretion in selecting the independent contractor or other third-party that will perform the service, the Company has the risk of loss in the event of cargo claims, and the Company bears credit risk with customer payments.  Accordingly, all such revenue billed to customers is classified as operating revenue and all corresponding payments to carriers for transportation services the Company arranges in connection with Brokerage and Intermodal activities and to independent contractor providers of revenue equipment are classified as purchased transportation expense.
	Allowance for Doubtful Accounts - Revenue is recognized when freight is delivered, creating a credit sale and an account receivable. Credit terms for customer accounts are typically on a net 30 day basis. 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. The Company 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. Historically, the Company has not had significant losses related to uncollectible accounts.
	Allowance for Doubtful Notes Receivable - The Company evaluates the collectability of notes and finance lease receivables on a customer-by-customer basis. The Company establishes an allowance for credit losses based on specific customer circumstances, payment patterns, credit risk changes, and historical loss experience. The Company reviews the adequacy of its allowance for doubtful notes receivable quarterly.  Uncollectible accounts are written off when deemed uncollectible, and notes receivable are presented net of an allowance for doubtful accounts. Historically, the Company has not had significant losses related to uncollectible accounts.
	Income Taxes - The Company accounts for income taxes under the asset and liability method. This method requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized as income in the period that includes the enactment date.
	The Company records a valuation allowance for deferred tax assets to the extent it believes these assets are not more likely than not to 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. A valuation allowance for deferred tax assets has not been deemed necessary due to the Company's profitable operations.
	The Company recognizes a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits.
	Financial Instruments- The Company's financial instruments include cash equivalents, investments held for trading, available-for-sale securities, trade receivables, notes receivable, accounts payable and long-term debt.  Due to the short-term nature of cash equivalents, trade receivables, and accounts payable, the fair value of these instruments approximates their recorded value.  Available-for-sale and trading securities consist of marketable equity and debt securities stated at fair value. Due to the variable interest rate, the fair value of long-term debt approximates fair value.
Concentration of Credit Risk - Financial instruments that potentially subject the Company to credit risk consist principally of trade receivables and notes receivable. Revenue for the Company's three largest customers accounted for approximately 11.7%, 11.0% and 10.0% of the total revenue for the years ended 2014, 2013 and 2012, respectively. As of December 31, 2014, balances due from the three largest customers account for approximately 6.7% of the total trade receivable balance compared to 6.5% as of December 31, 2013. Revenue from the Company's single largest customer represented approximately 4.3% of total revenue for the year ended December 31, 2014, and approximately 4.0% for the years ended 2013, and 2012. The balance due from the single largest customer accounts for approximately 3.2% of the total trade receivable balance as of December 31, 2014, compared to 1.2% as of December 31, 2013.
Earnings Per Share - A reconciliation of the numerator (net income) and denominator (weighted average number of shares outstanding) of the basic and diluted earnings per share ("EPS") computations for 2014, 2013, and 2012 are as follows (in thousands, except per share data):
		2014								2013						2012
		Net Income (numerator)			Shares (denominator)			Per Share Amount		Net Income (numerator)		Shares (denominator)		Per Share		Net Income (numerator)		Shares (denominator)		Per Share Amount
														Amount
Basic EPS		$	102,862			80,947		$	1.27	$	69,282		79,994	$	0.87	$	64,117		79,673	$	0.8
Effect of stock options & restricted stock			-			1,095					-		336				-		327
Diluted EPS		$	102,862			82,042		$	1.25	$	69,282		80,330	$	0.86	$	64,117		80,000	$	0.8
Certain shares of options, restricted stock units, and performance restricted stock units (“equity awards”) were excluded from the computation of diluted earnings per share because the equity award’s exercise prices were greater than the average market price of the common shares and the sum total of assumed proceeds resulted in few shares repurchased than the weighted equity awards outstanding hypothetically exercised per the treasury method. A summary of those shares for the years ended December 31, 2014, 2013, and 2012, respectively, is as follows:
		2014			2013			2012
Number of anti-dilutive shares			232,803			1,917,020			1,926,298
New Accounting Pronouncements
In June 2014, the FASB issued ASU 2014-12, Stock Compensation - Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. The amendments in this update require performance targets that could be achieved after the requisite service period be treated as performance conditions that affect the vesting of the award. The amendment is effective as of January 1, 2016 and we do not expect it to have an impact on our consolidated financial statements.
In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers. The main objective of this update is to require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. The guidance in this update supersedes virtually all present U.S. GAAP guidance on revenue recognition. The amendments to the standard require the use of more estimates and judgments than the present standards and require additional disclosures. The amendments are effective as of January 1, 2017 and we are currently evaluating this standard and our existing revenue recognition policies to determine which of our customer arrangements in the scope of the guidance will be affected by the new requirements and what impact they would have on our consolidated financial statements upon adoption of this standard.
Revision of Prior Period Reported Amounts
During the first quarter of 2014, we identified errors associated with income tax accounts reported in prior periods.  Specifically, the errors related to our income tax accounting for incentive stock options since the adoption of FAS 123R in 2006 and errors in recording required annual adjustments to the tax provision and taxes payable.   The aforementioned errors resulted in an overstatement of the deferred tax liability by $2,355,000, understatement of income tax payable by $262,000, understatement of additional paid-in capital by $779,000, and understatement of retained earnings by $1,314,000 as of December 31, 2013.  We have adjusted our previously reported income taxes payable, deferred tax liability, additional paid in capital, and retained earnings accounts as of January 1, 2013 to correct these errors and such adjustments are reflected in the accompanying condensed consolidated financial statements.
Pursuant to the guidance of SEC Staff Accounting Bulletin (“SAB”) No. 99, Materiality, we concluded that the errors were not material to any of our prior period financial statements. However, in accordance with SAB No. 108, Considering the Effects of Prior Year Misstatements when Quantifying Misstatement in the Current Year Financial Statements, the prior period financial statements were revised to facilitate comparability between current and prior year periods.
A reconciliation of the effects of the adjustments to our previously reported balance sheet as of December 31, 2013 follows:
		31-Dec-13
		(in thousands)
Account		As Previously			Adjustment			As Adjusted
		Reported
Accrued liabilities(1)		$	18,800		$	262		$	19,062
Total current liabilities			62,802			262			63,064
Deferred tax liability			142,504			(2,355	)		140,149
Total long term liabilities			191,879			(2,355	)		189,524
Total liabilities			254,681			(2,093	)		252,588
Additional paid-in capital			150,079			779			150,858
Retained earnings			396,032			1,314			397,346
Total Knight Transportation shareholders’ equity			551,495			2,093			553,588
Total shareholders' equity			552,440			2,093			554,533
-1	Income tax payable is included in Accrued Liabilities of our consolidated balance sheets.

Note_2_Fair_Value_Measurements

Note 2 - Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Text Block]	2.             Fair Value Measurements
	The Company's assets and liabilities that have been measured at fair value are based on principles set forth in ASC 820-10, Fair Value Measurements and Disclosure, for recurring and non-recurring fair value measurements of financial and non-financial assets and liabilities. This standard defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles, and expands disclosures about fair value measurements. This standard establishes a three-level hierarchy for fair value measurements based upon the significant inputs used to determine fair value.  Observable inputs are those obtained from market participants external to the Company, while unobservable inputs are generally developed internally, utilizing management's estimates, assumptions, and specific knowledge of the nature of the assets or liabilities and related markets.  The three levels are defined as follows:
	Level 1 – Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. An active market is defined as a market in which transactions for the assets or liabilities occur with sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2 – Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active (markets with few transactions), inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.) and inputs that are derived principally from or corroborated by observable market data correlation or other means (market corroborated inputs).
	Level 3 – Unobservable inputs, only used to the extent that observable inputs are not available, reflect the Company's assumptions about the pricing of an asset or liability.
	In accordance with the fair value hierarchy described above, the following table shows the fair value of the Company's financial assets and liabilities that are required to be measured on a recurring basis at fair value as of December 31, 2014 and December 31, 2013.
						Level One				Level Two				Level Three
		Balance at		Balance at		Balance at		Balance at		Balance at		Balance at		Balance at		Balance at
		31-Dec-14		31-Dec-13		31-Dec-14		31-Dec-13		31-Dec-14		31-Dec-13		31-Dec-14		31-Dec-13
		(In thousands)
	Assets:
	Available-for-sale Securities:
	Equity securities - common shares	$	26,884	$	17,454	$	26,884	$	17,454		-		-		-		-
	Restricted cash and investments:
	Money market funds	$	1,027	$	1,371	$	1,027	$	1,371		-		-		-		-
	Trading Securities:
	Debt securities - municipal securities	$	2,237	$	2,232		-		-	$	2,237	$	2,232		-		-
	We have certain marketable equity securities classified as available-for-sale securities, which are recorded at fair value with unrealized gains and losses, net of tax, as a component of "Accumulated other comprehensive income" in shareholders' equity on the accompanying consolidated balance sheets. Realized gains and losses on available-for-sale securities are included in the determination of net income. We use specific identification to determine the cost of securities sold, or amounts reclassified out of accumulated other comprehensive income into earnings.
	The following table shows the Company’s realized gains during the years ended December 31, 2014, 2013, and 2012, on certain securities that were held as available-for-sale. The cost of securities sold is based on the specific identification method and included in “Other income” in the accompanying consolidated statements of income.
		December 31,
		2014		2013		2012
		(in thousands)
	Sales proceeds	$	6,355	$	8,782	$	112
	Cost of securities sold		3,190		6,857		51
	Realized gain	$	3,165	$	1,925	$	61
	Realized gains, net of taxes	$	1,932	$	1,189	$	38
	As of December 31, 2014, our available-for-sale equity investments included in "Other long-term assets and restricted cash and investments" on the accompanying consolidated balance sheets, was approximately $26.9 million, including gross unrealized gains of approximately $20.0 million, or $12.2 million (net of tax). As of December 31, 2013, our available-for-sale investment balance was approximately $17.5 million, including gross unrealized gains of approximately $7.4 million, or $4.6 million (net of tax). The cost basis of these investments at December 31, 2014, and 2013, is approximately $6.9 million and $10.1 million, respectively.

Note_3_Line_of_Credit_and_Long

Note 3 - Line of Credit and Long-term Debt	12 Months Ended
	Dec. 31, 2014
Disclosure Text Block [Abstract]
Long-term Debt [Text Block]	3.             Line of Credit and Long-Term Debt
	The Company maintained a revolving line of credit with Wells Fargo Bank, which permitted revolving borrowings and letters of credit. Previously, the line of credit had been maintained at $150.0 million with interest at either the prime rate, or LIBOR plus 0.625%. In October 21, 2013, the Company increased this limit to $300.0 million, and going forward it will bear interest at either the prime rate or LIBOR plus 0.750%, determined at the time of borrowing. In the first quarter of 2015, the Company modified the loan agreement to extend the maturity date of the revolving line of credit to December 1, 2017. The Company had $134.4 million and $38.0 million outstanding under the line of credit as of December 31, 2014 and 2013, respectively. The weighted average variable annual percentage rate ("APR") for amounts borrowed in 2014 was 0.91%, and 0.84% for amounts borrowed in 2013. Borrowing under the line of credit is recorded in the "Long-term debt" line of the consolidated balance sheets. In connection with our self-insurance program, as of December 31, 2014, the Company also utilized $24.3 million of the line of credit for letters of credit issued to various regulatory authorities. Considering the increase in the line of credit limit noted above, the Company has $141.3 million available for future borrowings. After consideration of fees incurred for the unused portion of our line of credit, our weighted average variable annual percentage rate ("APR") for the year ended December 31, 2014 was 1.31%, and 1.04% for the year ended December 31, 2013. We borrowed approximately $112.0 million from our line of credit in connection with an acquisition on October 1, 2014. See Note 12 for additional information with respect to this acquisition. The Company is obligated to comply with certain financial and other covenants under the line of credit agreement and was in compliance with such covenants at December 31, 2014.

Note_4_Income_Taxes

Note 4 - Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	4.             Income Taxes
	Income tax expense consists of the following (in thousands):
		2014			2013			2012
	Current income taxes:
	Federal	$	42,101		$	46,445		$	42,280
	State		8,648			5,573			4,709
			50,749			52,018			46,989
	Deferred income taxes:
	Federal		12,644			(5,520	)		(2,403	)
	State		4,416			182			428
			17,060			(5,338	)		(1,975	)
		$	67,809		$	46,680		$	45,014
	The effective income tax rate is different than the amount that would be computed by applying statutory corporate income tax rates to income before income taxes. The differences are summarized as follows (in thousands):
		2014			2013			2012
	Tax at the statutory rate (35%)	$	60,141		$	40,846		$	38,422
	State income taxes, net of federal benefit		8,492			3,804			3,489
	Nondeductible driver per diem		1,885			1,807			1,989
	Other, net		(2,709	)		223			1,114
		$	67,809		$	46,680		$	45,014
	The net effect of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities at December 31, 2014 and 2013 are as follows (in thousands):
		2014			2013
	Short-term deferred tax assets (liabilities):
	Claims accrual	$	6,322		$	2,460
	Stock options		-			2,254
	Investments		(2,066	)		-
	Prepaid expenses deducted for tax purposes		(2,952	)		(2,237	)
	Other, net		1,883			882
	Short-term deferred tax assets, net	$	3,187		$	3,359
	Long-term deferred tax liabilities (assets):
	Property and equipment depreciation	$	161,209		$	143,488
	Claims accrual		(4,482	)		(984	)
	Stock options		(2,847	)		-
	Investments		7,807			-
	Other, net		320			-
	Long-term deferred liabilities, net	$	162,007		$	142,504
	For the years ended December 31, 2014, 2013, and 2012, the Company does not have any uncertain tax positions, nor any unrecognized tax benefits based upon an analysis of the Company's historic and future tax positions. There are no tax uncertainties for which it is reasonably possible an amount of unrecognized tax benefit should be recognized. 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 Topic 740.
	The Company files federal and state income tax returns with varying statutes of limitations. The 2011 through 2014 tax years generally remain subject to examination by the federal authority, and the 2010 through 2014 tax years generally remain subject to examination by state tax authorities. The Company does not believe the unrecognized tax benefits will change significantly over the next 12 months.

Note_5_Commitments_and_Conting

Note 5 - Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	5.             Commitments and Contingencies
	a.             Purchase Commitments
	The Company's purchase commitments for 2015 total $191.3 million, which primarily consists of revenue equipment, net of equipment trade-ins from contracted vendors, and a carry forward of approximately $12.8 million from 2014 contracts. The Company generally has the option to cancel with advanced notice ranging from 9 weeks to 90 days prior to the scheduled production.
	b.             Investment Commitments
	The Company's commitment to invest in TRP is $5.5 million. The Company's commitment to invest in TRP III is $15.0 million. As of December 31, 2014, the Company has contributed approximately $10.9 million to TRP III, leaving an outstanding commitment of $4.1 million as of December 31, 2014.
	c.             Operating Leases
	The Company periodically leases revenue equipment, certain service center building facilities, and communication equipment under non-cancelable operating leases. The Company also has operating leases for trailer storage. Operating lease expense under operating leases was approximately $2.8 million, $2.2 million, and $2.4 million for the years ended December 31, 2014, 2013, and 2012, respectively. Operating lease expense is included as an operating expense under "Miscellaneous operating expenses" in the consolidated statements of income.
	Future minimum lease payments under non-cancelable operating leases as of December 31, 2014 are as follows:
	Year Ending	Amount
	December 31,	(In thousands)
	2015	$	2,928
	2016		2,679
	2017		2,699
	2018		1,362
	Total	$	9,668
	d.             Other
	The Company is involved in certain claims and pending litigation arising in the normal course of business.  These proceedings primarily involve claims for personal injury or property damage incurred in the transportation of freight or for personnel matters.  The Company maintains insurance to cover liabilities arising from the transportation of freight in amounts in excess of self-insurance retentions, and accrues for estimated self-insured claims liabilities as described in Note 6.  Based on present knowledge of the facts and, in certain cases, advice of outside counsel, management believes the resolution of claims and pending litigation, taking into account existing reserves, will not have a materially adverse effect on the Company's financial position or results of operations.  However, the final disposition of these matters and the impact of such final dispositions cannot be determined at this time.
	The Company is also involved in certain class action litigation in which the plaintiffs allege claims for failure to provide meal and rest breaks, unpaid wages, unauthorized deductions and other items.  Based on its knowledge of the facts and advice of outside counsel, management does not believe the outcome of the litigation is likely to have a materially adverse effect on the Company's financial position or results of operations.  However, the final disposition of these matters and the impact of such final dispositions cannot be determined at this time.

Note_6_Claims_Accrual

Note 6 - Claims Accrual	12 Months Ended
	Dec. 31, 2014
Claims Accrual [Abstract]
Claims Accrual [Text Block]	6.             Claims Accrual
	The primary claims arising for the Company consist of auto liability (personal injury and property damage), cargo liability, collision, comprehensive and workers' compensation. The Company is insured against auto liability claims under a SIR policy with retention ranging from $1.0 million to $3.0 million per occurrence and in some years, depending on the applicable policy year, the Company has been responsible for aggregate losses up to $1.5 million. For the policy year February 1, 2013 to January 31, 2014 the Company's SIR was $3.0 million with no responsibility for additional aggregate losses. For the policy period February 1, 2014 to March 1, 2015 the Company's SIR is $2.5 million with no additional responsibility for "aggregate" losses. The Company is also self-insured for workers' compensation coverage, with a self-retention level of a maximum $500,000 per occurrence. The Company establishes reserves to cover these self-insured liabilities and maintains insurance to cover liabilities in excess of those amounts. The Company's insurance policies provide for excess personal injury and property damage liability up to a total of $105.0 million per occurrence, which also includes a separate $2.5 million dollar aggregate deductible.
	The Company also maintains excess coverage for employee medical expenses and hospitalization. The self- retention amount for employee medical health was $225,000 per claimant for 2014 and 2013, and will remain this amount for 2015.
	The Company's claims reserves are classified separately between current and long-term in the balance sheet. The current and long-term balance of the Company's claims reserves at December 31, 2014 and 2013 are as follows:
			2014			2013
			(In thousands)
	Auto reserves		$	18,075		$	15,432
	Workers' compensation reserves			8,728			6,479
	Employee medical reserves			3,234			2,594
	Total reserves		$	30,037		$	24,505
	Current portion		$	18,532		$	15,616
	Long-term portion		$	11,505		$	8,889
	A reconciliation of the beginning and ending amount of the Company's claims reserves for the years ended December 31, 2014 and 2013 is as follows:
			2014			2013
			(In thousands)
	Beginning Balance		$	24,505		$	26,232
	Acquisition (1)			3,209			-
	Provisions recorded			49,135			43,797
	Claims paid and direct expenses			(46,812	)		(45,524	)
	Total reserves		$	30,037		$	24,505
		-1	Addition to claims reserve following acquisition of Barr-Nunn.
	The provision recorded for the year ended December 31, 2014 is comprised of $30.9 million for insurance and claims expense, which is included in the "Insurance and claims" line of the consolidated statements of income, $7.8 million for workers' compensation expense, and $10.4 million for medical expense, both of which are included in the "Salaries, wages and benefits" line of the consolidated statements of income. The provision recorded for the year ended December 31, 2013 is comprised of $29.1 million for insurance and claims expense, $5.5 million for workers' compensation expense, and $9.2 million for medical expense.

Note_7_Related_Party_Transacti

Note 7 - Related Party Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related Party Transactions Disclosure [Text Block]	7.             Related Party Transactions
	We have provided general business loans to US West Agriculture Exporters, LLC, ("USW") a company that transacted business with our drayage operation, and in which Larry Knight is a 33% owner. Larry Knight is an employee of the Company and the brother of Kevin Knight and Keith Knight, our former Chief Executive Officer and former Chief Operating Officer, respectively. The loan balance including interest due from USW at December 31, 2013, was approximately $748,000, for which the Company received full payment during the first quarter in 2014. The principal loan and interest balance was recorded in "Related party notes and interest receivable" on our consolidated balance sheets.

Note_8_Shareholders_Equity

Note 8 - Shareholders' Equity	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	8.             Shareholders' Equity
	During 2014, 2013, and 2012, certain non-employee Board of Director members received annual director fees through the issuance of common stock in equivalent shares. The table below reflects this activity for the years as presented.
		2014		2013		2012
	Annual director fees paid through stock issuance	$	200,484	$	167,946	$	148,437
	Shares of common stock issued		8,828		9,885		9,040
	Dividends paid per common share	$	0.24	$	0.24	$	0.74

Note_9_Stockbased_Compensation

Note 9 - Stock-based Compensation and Employee Benefit Plans	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	9.             Stock Based Compensation and Employee Benefit Plans
	a.             Stock-Based Compensation
	In May 2012, our shareholders approved the 2012 Equity Compensation Plan (the "2012 Plan").  The 2012 Plan replaced the Amended and Restated 2003 Stock Option and Equity Compensation Plan, as amended and restated in May 2009 (the "2003 Plan").  Grants outstanding under the 2003 Plan continue in force and effect, but any grants of stock-based compensation after May 18, 2012, were made under the 2012 Plan.
	The 2012 Plan is administered by the Compensation Committee of the Board of Directors (the "Compensation Committee").  The Compensation Committee has discretion to determine the number of shares subject to each grant and the terms and conditions of each grant, subject to the general limitations of the 2012 Plan, but in any calendar year, no single grant may exceed 650,000 shares.  The Compensation Committee may award incentive stock options, non-qualified stock options, restricted stock grants, restricted stock units, performance based restricted stock units, or stock appreciation rights to employees and officers.  Incentive stock options are designed to comply with the applicable provisions of the Internal Revenue Code (the "Code") and are subject to restrictions within the Code.  Vesting schedules for grants are set by the Compensation Committee and vary according to the goals of the grant.  Grants, including stock options, must be granted with exercise price equal to the fair market value, determined by the closing price of the stock on the date the grant is made, as reported by the New York Stock Exchange.  The exercise price of stock options granted may not be modified.  Most stock options granted by the Company cannot be exercised until at least one (1) year after the date of grant and are forfeited upon termination of employment for reasons other than death, disability, or retirement.  The 2012 Plan reserves 4 million shares for the grant of equity compensation awards, of which 200,000 shares are reserved for issuance to outside directors.  The 2012 Plan will terminate on May 16, 2022.
	For the periods presented in these consolidated financial statements, the Company’s independent directors have received annual compensation that is payable 50% in cash and 50% in common stock.  In first quarter of 2015 the Compensation Committee adopted a new Directors Equity Grant Policy under the 2012 Plan, pursuant to which directors will be permitted to receive their annual director compensation as follows: (i) 50% of the director’s annual fee in cash and 50% of the director’s annual fee in stock grants; or (ii) in additional stock grants in round increments of 10% in excess of 50% of the director’s annual fee through the issuance of stock grants; or (iii) 100% in stock grants.  Stock grants may be made either as grants of restricted stock or as restricted stock units.  The Directors Equity Grant Policy is consistent with compensation grants made to directors under the 2012 Plan.  The Directors Equity Grant Policy is effective March 1, 2015.
	Stock-based compensation charges were approximately $4.5 million, $2.8 million, and $6.3 million for the years ended December 31, 2014, 2013, and 2012, respectively, which reduced income from operations accordingly. Stock-based compensation expense recognized is based on awards ultimately expected to vest and has been reduced for estimated forfeitures. ASC 718 requires forfeitures to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.
	In 2012, the Compensation Committee of the Board of Directors approved the accelerated vesting of certain stock options issued prior to 2009, resulting in approximately $4.0 million of pre-tax stock compensation expense ($3.9 million after tax) in that year.
	The Company received $24.4 million, $4.3 million, and $3.6 million in cash from the exercise of stock options during the years ended December 31, 2014, 2013 and 2012, respectively. The excess tax benefit realized for the tax deductions from the exercise of options of the share-based payment arrangements was approximately $5.3 million for the year ended December 31, 2014, zero for the year ended December 31, 2013, and approximately $30,000 for the year ended December 31, 2012. This tax benefit also decreased cash provided by operating activities, and increased cash provided by financing activities by the same amount for all years presented.
	The fair value of each option grant is estimated on the date of grant using the Black-Scholes option valuation model. Listed below are the weighted average assumptions used for the fair value computation:
			Year Ended December 31,
			2014				2013			2012
	Dividend yield (1)			1.06	%			1.54	%	N/A
	Expected volatility (2)			28.01	%			24.92	%	N/A
	Risk-free interest rate (3)			0.82	%			0.34	%	N/A
	Expected terms (years) (4)			2.74				2.74		N/A
	Weighted average fair value of options granted		$	3.96			$	2.25		N/A
	-1	The dividend yield is based on the Company's historical experience and future expectation of dividend payouts.
	-2	The Company analyzed the volatility of its stock using historical data for the past five years to through the end of the most recent period to estimate expected volatility.
	-3	The risk-free interest rate assumption is based on U.S. Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the stock option award.
	-4	The expected terms of employee stock options represents the weighted-average period the stock options are expected to remain outstanding and has been determined based on historical exercise behavior.
	As of December 31, 2014, there was approximately $1.9 million of unrecognized compensation cost related to stock option compensation awards. That cost is expected to be recognized over a weighted-average period of 1.9 years, and a total period of 4.0 years.
	A summary of the award activity for the years ended December 31, 2014, 2013, and 2012 is presented below:
			2014								2013								2012
			Options				Weighted				Options				Weighted				Options				Weighted
							Average								Average								Average
							Exercise								Exercise								Exercise
							Price								Price								Price
	Outstanding at beginning of year			3,374,846			$	16.26				3,424,806			$	15.99				3,823,585			$	15.8
	Granted			399,550				22.74				429,800				15.62				-			$	0
	Exercised			(1,551,400	)			15.73				(345,302	)			12.6				(281,993	)		$	12.85
	Forfeited and Expired			(80,025	)			17.9				(134,458	)			16.78				(116,786	)		$	17.13
	Outstanding at end of year			2,142,971				17.8				3,374,846				16.26				3,424,806			$	15.99
	Vested and exercisable at end of year			1,383,888				16.86				2,828,365				16.27				3,174,843			$	15.86
	Weighted average fair value of options granted during the period							3.96								2.25							N/A
	As of December 31, 2014, the number of options that were currently vested and expected to become vested was 2,083,959. These options have a weighted-average exercise price of $17.72, a weighted-average contractual remaining term of 2.9 years, and an aggregate intrinsic value of $33.2 million.
	The following table summarizes information about stock options to purchase the Company's common stock at December 31, 2014:
	Range of				Shares				Weighted Avg.				Weighted Avg.				Number Vested				Weighted
	Exercise				Outstanding				Contractual				Exercise Price				and Exercisable				Avg. Exercise
	Prices								Years				Per Share								Price Per
									Remaining												Share for
																					Vested and
																					Exercisable
	$12.63	-	14.73			54,995				0.58			$	14.4				52,395			$	14.45
	$14.74	-	16.83			834,187				2.62			$	15.41				540,854			$	15.32
	$16.84	-	18.94			854,289				2.9			$	18.1				770,889			$	18.01
	$18.95	-	33.27			399,500				4.1			$	22.6				19,750			$	20.21
	Overall Total					2,142,971				2.95			$	17.8				1,383,888			$	16.86
	The total intrinsic value of options exercised during the twelve-month period was $17.8 million, $1.5 million, and $1.3 million in 2014, 2013, and 2012, respectively. Based on the market price as of December 31, 2014, the intrinsic value of options outstanding as of December 31, 2014 was approximately $34.0 million, and the intrinsic value of options exercisable for the same period was approximately $23.2 million. The weighted average remaining contractual life as of December 31, 2014 for vested and exercisable options is 2.3 years.
	Since 2009, the Company has issued restricted stock units (“RSUs”) to its employees. The Company's RSU program consists of service based awards that vest gradually over a period ranging from 5 to 13 years. In 2012, the Company issued 41,000 RSUs with a market value of $16.76 per share based on the closing market price on the date of issuance. In 2013, the Company issued 183,111 RSUs with a market value ranging from $15.62 to $17.87 per share based on the closing market price on the date of issuance. In 2014, the Company issued 17,017 RSUs with a market value ranging from $22.61 to $33.27 per share based on the closing market price on the date of issuance. Stock compensation expense for these RSUs is being amortized using the straight-line method over the requisite service period. As of December 31, 2014, the Company had approximately $13.6 million of unrecognized compensation expense related to restricted stock awards, which will be recognized over a weighted average period of 4.0 years.
	RSUs not yet vested are entitled to accumulate quarterly cash dividends that are paid to shareholders holding outstanding shares of the Company's common stock. Accrued dividends are paid to recipients as the RSUs vest. Accrued dividends are forfeited if RSUs are canceled or terminated. Dividends paid under the RSU program are charged to retained earnings.
	The following tables summarize the Company's restricted stock award activity for the fiscal years ended December 31, 2014, 2013, and 2012:
			2014								2013								2012
			Number of				Weighted				Number of				Weighted				Number of				Weighted
			Restricted				Average				Restricted				Average				Restricted				Average
			Stock Awards				Grant Date				Stock Awards				Grant Date				Stock Awards				Grant Date
							Fair Value								Fair Value								Fair Value
	Unvested at January 1
	Unvested at January1,			1,213,698			$	16.04				1,210,532			$	16.04				1,325,817			$	16.01
	Granted			17,017			$	27.63				183,111			$	15.95				41,000			$	16.76
	Vested			(128,659	)		$	16.07				(130,265	)		$	16.01				(114,605	)		$	16
	Forfeited and Expired			(28,510	)		$	16.23				(49,680	)		$	15.75				(41,680	)		$	15.97
	Outstanding (unvested) at end of year			1,073,546			$	16.22				1,213,698			$	16.04				1,210,532			$	16.04
	Beginning in 2014, we issued performance restricted stock units (“PRSUs”) to selected key employees that may be earned based on revenue growth and return on assets, and may then be modified based on our total shareholder return, as defined, over the three-year period. The primary award adjustment may range from 0 percent to 150 percent of the initial grant, based upon performance achieved. The primary award modifier, which would multiply the adjusted primary award by 75 percent to 125 percent, is measured by determining the percentile rank of the total shareholder return of Knight common stock in relation to the total shareholder return of a peer group for the three-year period. The final award will be based on performance achieved in accordance with the scale set forth in the plan agreement. Performance restricted stock units do not earn dividend equivalents.
	During 2014 we granted 181,112 PRSUs. The performance measurement period for this award is January 1, 2014 to December 31, 2016. This award will vest January 31, 2018, or thirteen months following the expiration of the performance period. The fair value of each PRSU grant is estimated on the date of grant using the Monte Carlo Simulation valuation model. Listed below are the weighted average assumptions used for the fair value computation:
		Year Ended December 31, 2014
Dividend yield (1)			1.06	%
Expected volatility (2)			26.11	%
Average peer volatility(2)			36.01	%
Average peer correlation coefficient(3)			0.5796
Risk-free interest rate (4)			0.66	%
Expected term (5)			2.8
Weighted average fair value of PRSUs granted		$	23.85
-1	The dividend yield, used to project stock price to the end of the performance period, is based on our historical experience and future expectation of dividend payouts. Total shareholder 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	We (or peer company) estimated volatility using our (or their) 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 U.S. Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the performance award.
-5	Since Monte Carlo valuation is an open form model that uses an expected life commensurate with the performance period, the expected life of the PRSUs was assumed to be the period from the grant date to the end of the performance period.
Our policy is to recognize compensation cost on a straight-line basis over the requisite service period.
As of December 31, 2014, there was $3.4 million of unrecognized compensation cost related to performance awards. That cost is expected to be recognized over a weighted-average period and total period of 3.1 years.
b.             401(k) Profit Sharing Plan
The Company has a 401(k) profit sharing plan (the "Plan") for all employees who are 19 years of age or older and have completed one year of service with the Company. Beginning in January 2015, all employees 18 years or older and who have completed six months of service will be eligible to participate in the Plan. The Plan provides for a mandatory matching contribution equal to 50% of the amount of the employee's salary deduction not to exceed $1,000 annually per employee; this limit was increased in 2014 from $850 in 2013. The limit of the mandatory matching contribution for 2015 has been increased to the amount of employee’s salary deductions not to exceed $1,150. The Plan also provides for a discretionary matching contribution. In 2014, 2013, and 2012, there were no discretionary contributions. Employees' rights to employer contributions vest after five years from their date of employment. The Company's mandatory matching contribution was approximately $451,000, $326,000, and $266,000 in 2014, 2013, and 2012, respectively.

Note_10_Company_Share_Repurcha

Note 10 - Company Share Repurchase Program	12 Months Ended
	Dec. 31, 2014
Disclosure Text Block Supplement [Abstract]
Treasury Stock [Text Block]	10.           Company Share Repurchase Program
	On November 13, 2008, the Company's Board of Directors unanimously authorized the repurchase of up to 3.0 million shares of the Company's common stock. As of December 31, 2010, there were 2,020,956 shares remaining under the 2008 authorization. On May 19, 2011, the Company's Board of Directors unanimously authorized the repurchase of an additional 10.0 million shares of the Company's common stock. The repurchase authorization is intended to afford the Company flexibility to acquire shares opportunistically in future periods and does not indicate an intention to repurchase any particular number of shares within a definite timeframe. Any repurchases would be effected based upon share price and market conditions.
	No shares have been repurchased under the share repurchase program during the years ended December 31, 2014, 2013, and 2012. As of December 31, 2014, there were 7,438,556 shares remaining for future purchases under the repurchase program. The repurchase authorization will remain in effect until the share limit is reached or the program is terminated.

Note_11_Segment_Information

Note 11 - Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	11.           Segment Information
	The Company has two operating segments: (i) the Trucking segment comprised of three operating units (Dry Van, Refrigerated, and Drayage), and (ii) the Logistics segment comprised of two operating units (Brokerage and Intermodal). The Company also provides logistics, freight management and other non-trucking services through its Logistics businesses. Through its Trucking and Logistics segment capabilities, the Company is able to transport, or can arrange for the transportation of, general commodities for customers throughout the United States and parts of Canada and Mexico.
	Prior to fourth quarter 2013, the Company aggregated the Trucking and Logistics segments in accordance with relevant accounting guidance regarding segment reporting. Based on the Company's 2013 evaluation, the Company concluded that because of evolving events and changes to its business, that separate segment reporting of the Company's Trucking business and Logistics business is appropriate.
	The Company, in determining its reportable operating segments, focuses on financial information such as operating revenues and expenses, operating income, operating ratios, and other key operating statistics common in the industry. The chief operating decision makers also use this information to evaluate segment performance and allocate resources to the Company's operations.
	The Company's operating segments provide transportation and related services for one another. Such services are billed at cost, and no profit is earned. Such intersegment revenues and expenses are eliminated in the Company's consolidated results.
	The following table sets forth revenue and operating income between the Trucking and Logistics segments for the years ended December 31, 2014, 2013, and 2012.
			2014								2013						2012
	Revenues:		$				%				$			%			$			%
	Trucking Segment		$	892,124				80.9	%		$	822,188			84.8	%	$	836,357			89.3	%
	Logistics Segment			214,378				19.4				151,194			15.6			105,794			11.3
	Subtotal			1,106,502								973,382						942,151
	Intersegment Eliminations Trucking			(65	)			0				(120	)		0			(112	)		0
	Intersegment Eliminations Logistics			(4,105	)			(0.3	)			(4,025	)		(0.4	)		(6,003	)		(0.6	)
	Total		$	1,102,332				100	%		$	969,237			100	%	$	936,036			100	%
	Operating Income:
	Trucking Segment		$	147,424				90.6	%		$	106,167			93.2	%	$	103,013			95.1	%
	Logistics Segment			15,298				9.4				7,742			6.8			5,254			4.9
	Total		$	162,722				100	%		$	113,909			100	%	$	108,267			100	%
	TruckingSegment Information
	The Trucking units operate large modern company-owned tractor fleets and use independent contractors to provide various transportation solutions, including multiple stop pick-ups and deliveries, dedicated equipment and personnel, on-time expedited pick-ups and deliveries, specialized driver training, and other truckload services. Revenues are generally set at a predetermined rate per mile or per load for the Trucking services. In addition, revenue streams are also generated by charging for tractor and trailer detention, loading and unloading activities, dedicated services, and other specialized services, as well as through the collection of fuel surcharges to mitigate the impact of increases in the cost of fuel.
	The primary measurement the Company uses to evaluate the profitability of the Trucking segment is operating ratio, measured both on a GAAP basis (operating expenses expressed as a percentage of revenue) and non-GAAP basis used by many in the Company's industry (operating expenses, net of Trucking fuel surcharge revenue, expressed as a percentage of Trucking revenue, excluding Trucking fuel surcharge revenue). The Company believes the second method allows them to more effectively compare periods while excluding the potentially volatile effect of changes in fuel prices. The tables below compare operating ratio using both methods.
	The following table sets forth the Trucking segment operating ratio on a GAAP basis.
	GAAP Presentation:		2014								2013						2012
	Trucking (amounts in thousands)		$				%				$			%			$			%
	Revenue		$	892,124							$	822,188					$	836,357
	Operating expenses			744,700				83.5				716,021			87.1			733,344			87.7
	Operating income		$	147,424							$	106,167					$	103,013
	The following table sets forth the Trucking segment operating ratio as if fuel surcharges are excluded from total revenue and instead reported as a reduction of operation expenses, excluding intersegment activity.
	Non-GAAP Presentation(1):		2014								2013						2012
	Trucking (amounts in thousands)		$				%				$			%			$			%
	Revenue		$	892,124							$	822,188					$	836,357
	Less: Trucking fuel surcharge revenue			(176,347	)							(177,386	)					(183,885	)
	Less: Intersegment transactions			(65	)							(120	)					(112	)
	Revenue, net of fuel surcharge and intersegment transactions			715,712								644,682						652,360
	Operating expenses			744,700								716,021						733,344
	Less: Trucking fuel surcharge revenue			(176,347	)							(177,386	)					(183,885	)
	Less: Intersegment transactions			(65	)							(120	)					(112	)
	Operating expenses, net of fuel surcharge and intersegment transactions			568,288				79.4				538,515			83.5			549,347			84.2
	Operating income		$	147,424							$	106,167					$	103,013
	-1	These items represent non-GAAP financial measures and are not substitutes for, and should be considered in addition to, the GAAP financial measures presented in the previous table.
	The Company's Trucking segment requires substantial capital expenditures for purchases of new revenue equipment.  Total depreciation and amortization expense for the Trucking Segment was approximately $88.2 million, $81.0 million, and 79.7 million in 2014, 2013, and 2012, respectively.
	LogisticsSegment Information
	Logistics revenue is generated primarily by the Brokerage and Intermodal operating units, which charges a predetermined rate per mile or per load for arranging freight transportation for its customers. The Company also provides logistics, freight management and other non-trucking services through its Logistics business. Additional revenue is generated by offering specialized logistics solutions (including, but not limited to, origin management, surge volumes, disaster relief, special projects, and other logistics needs). Logistics revenue is mainly affected by the rates the Company is able to negotiate with clients, the freight volumes that are shipped through third-party capacity providers and the Company's ability to secure qualified third-party capacity providers to transport customer freight. This segment has seen continued growth in the number of shipments serviced by the Brokerage and Intermodal operating units, and contributed to the improved productivity and revenue realized in 2014.
	The following table sets forth the Logistics segment revenue, other operating expenses, and operating income.
			2014								2013						2012
	Logistics (amounts in thousands)		$				%				$			%			$			%
	Revenue		$	214,378							$	151,194					$	105,794
	Other operating expense			199,080				92.9				143,452			94.9			100,540			95
	Operating income		$	15,298							$	7,742					$	5,254
	The following table sets forth the Logistics revenue, operating expenses, and operating income, excluding intersegment transactions.
			2014								2013						2012
	Logistics (amounts in thousands)		$				%				$			%			$			%
	Revenue		$	214,378							$	151,194					$	105,794
	Less: Intersegment transactions			(4,105	)							(4,025	)					(6,003	)
	Revenue excluding intersegment transactions			210,273								147,169						99,791
	Operating expenses			199,080								143,452						100,540
	Less: Intersegment transactions			(4,105	)							(4,025	)					(6,003	)
	Operating expenses excluding intersegment transactions			194,975				92.7				139,427			94.7			94,537			94.7
	Operating income		$	15,298							$	7,742					$	5,254
	The Company primarily measures the Logistics segment's profitability by reviewing the gross margin percentage (revenue, less purchased transportation expense, expressed as a percentage of revenue) and the operating income percentage. The gross margin percentage can be affected by customer rates and the costs of securing third-party capacity providers. The Company's third-party capacity providers are generally not subject to long-term or predetermined contracted rates, and the operating results could be affected if the availability of third-party capacity providers or the rates for such providers change in the future. The following table lists the gross margin percentage for the Company's Brokerage and Intermodal businesses.
					2014					2013				2012
	Combined Brokerage and Intermodal gross margin percent (1)					15	%				12.5	%			13.2	%
	-1	Gross margin percentage is based on revenue net of intersegment elimination.
	The Company's Logistics segment does not require significant capital expenditures and is not asset-intensive like the Trucking segment. Total Logistics segment depreciation and amortization expense is primarily attributed to equipment leased to third parties, which totaled to approximately $4.7 million, $5.1 million, and $5.3 million in 2014, 2013, and 2012, respectively.
No segmental asset information is provided as the company does not prepare balance sheets by segment, and the chief operating decision makers do not review segment assets to make operating decisions.

Note_12_Acquisition_of_BarrNun

Note 12 - Acquisition of Barr-Nunn Transportation, Inc.	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	Note 12. Acquisition of Barr-Nunn Transportation, Inc.
	On October 1, 2014, the Company entered into a Stock Purchase Agreement for the purchase of 100% of the outstanding stock of Barr-Nunn Transportation, Inc., and certain affiliates (“Barr-Nunn”).
	Barr-Nunn is a transportation services carrier headquartered near Des Moines, Iowa, offering dry van truckload transportation and logistics services, with its primary operating territory in the eastern United States.
	Barr-Nunn had an enterprise value at closing of approximately $112.4 million (before the potential earn-out payment discussed below). At closing, the Company paid approximately $111.2 million of total consideration for the stock and certain real estate, which was paid in cash and funded through borrowing under the Company’s line of credit on the date of the transaction. The purchase price was adjusted in December 2014 pursuant to a customary working capital adjustment, which produced a credit of approximately $0.7 million to the Company, resulting in total consideration paid of $110.5 million, which remains subject to customary adjustments. The transaction also provides for a potential one-time earn-out payment of up to $3.5 million, subject to achievement of an operating income target for Barr-Nunn for the four fiscal quarters after closing and retention of key personnel. The Stock Purchase Agreement 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 Stock Purchase Agreement contains customary representations, warranties, covenants, and indemnification provisions. At closing, $8.0 million of the purchase price was placed in escrow to secure the Sellers' indemnification obligations.
	The results of the acquired business have been included in the consolidated financial statements since the date of acquisition and represented 12.0% of consolidated total assets as of December 31, 2014, and 3.0% of total revenue for 2014, and 3.8% of net income for 2014. The Company recorded approximately $429,000 of acquisition related expenses, which are included within “Miscellaneous operating expenses” in the consolidated statement of income for the year ended December 31, 2014.
	The following unaudited pro forma consolidated results of operations for the years ended December 31, 2014, 2013, and 2012 assume that the acquisition of Barr-Nunn occurred as of January 1, 2012.
		(Unaudited)
		Years ended
		December 31,			December 31,		December 31,
		2014			2013		2012
		(in thousands)
	Total revenue	$	1,192,745		$	1,087,790	$	1,052,711
	Net income		109,787			78,274		72,376
	These pro forma amounts do not purport to be indicative of the results that would have actually been obtained if the acquisition had occurred at the beginning of the periods presented or that may be obtained in the future.
	The allocation of the purchase price is provided in the tables below. The final purchase price allocation was subject to a post-closing working capital adjustment, and remains subject to earn-out amounts achieved (if any) and other adjustments. The goodwill recognized represents expected synergies from combining the operations of the Company with Barr-Nunn including enhanced service offerings and sharing best practices in terms of driver recruiting and retention, , as well as other intangible assets that did not meet the criteria for separate recognition. All tax goodwill recognized in the transaction is deductible for tax purposes over 15 years, and no deferred taxes were recorded.
	ALLOCATION OF PURCHASE PRICE	(in thousands)
	Total fair value of consideration transferred	$	110,517
	Allocated to:
	Historical book value of Barr-Nunn’s assets and liabilities (excluding cash)	$	71,656
	Adjustments to recognize assets and liabilities at acquisition-date fair value:
	Property, and equipment		3,349
	Liabilities		-5,023
	Fair value of tangible net assets acquired		69,982
	Identifiable intangibles at acquisition-date fair value		3,700
	Excess of consideration transferred over the net amount of assets and liabilities recognized, including $3.5 million attributable to the fair value of a potential earn-out obligation (goodwill)	$	36,835
	Excess of consideration transferred over the net amount of assets and liabilities recognized (goodwill) is still subject to final purchase price adjustment related to earn-out amounts achieved (if any) and other adjustments.
	The assets and liabilities associated with Barr-Nunn were recorded at their fair values as of the acquisition date and the amounts are as follows:
		(in thousands)
	Trade receivables	$	11,380
	Other current assets		2,316
	Property and equipment		68,444
	Goodwill		36,835
	Intangible assets		3,700
	Total assets		122,675
	Accounts payable		(3,311	)
	Accrued liabilities		(5,638	)
	Claims accruals		(3,209	)
	Total consideration transferred	$	110,517
	TOTAL PURCHASE PRICE CONSIDERATION	(in thousands)
	Cash paid pursuant to Stock Purchase and Real Estate Agreements	$	110,517
	The Stock Purchase Agreement also provides for a potential one-time earn-out payment of up to $3.5 million, contingent upon achievement of an operating income target for Barr-Nunn and retention of key personnel for the four fiscal quarters ending September 30, 2015. This contingent liability was estimated as of the date of the transaction and has been included in the adjustments to liabilities at the transaction-date fair value recorded. The fair value of the contingent liability is subject to change based on actual results of Barr-Nunn over the four fiscal quarters ending September 30, 2015.

Note_13_Quarterly_Financial_Da

Note 13 - Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	13.           Quarterly Financial Data (unaudited)
	The following table sets forth certain unaudited information about the Company's revenue and results of operations on a quarterly basis for 2014 and 2013 (amount in thousands, except per share data):
		2014
		31-Mar		30-Jun		30-Sep		31-Dec
	Revenue, before fuel surcharge		205,596		218,908		227,829		273,653
	Income from operations		31,250		38,899		39,791		52,782
	Net income attributable to Knight		19,064		25,761		25,100		32,938
	Earnings per common share:
	Basic	$	0.24	$	0.32	$	0.31	$	0.4
	Diluted	$	0.23	$	0.31	$	0.31	$	0.4
		2013
		31-Mar		30-Jun		30-Sep		31-Dec
	Revenue, before fuel surcharge		189,600		200,104		195,847		206,300
	Income from operations		25,544		31,925		24,274		32,165
	Net income attributable to Knight		15,183		18,939		15,059		20,101
	Earnings per common share:
	Basic	$	0.19	$	0.24	$	0.19	$	0.25
	Diluted	$	0.19	$	0.24	$	0.19	$	0.25
	The Company acquired 100% of the outstanding stock of Barr-Nunn on October 1, 2014 and therefore the operating results of the Company for the fourth quarter of 2014 includes the operating results of Barr-Nunn for the period of October 1, 2014 to December 31, 2014.

Note_14_Subsequent_Events

Note 14 - Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events [Text Block]	14.           Subsequent Events
	The Company has evaluated events occurring subsequent to December 31, 2014 through the filing date of this Annual Report on Form 10-K for disclosure. No events occurred requiring disclosure.

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts and Reserves	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	SCHEDULE II
	KNIGHT TRANSPORTATION, INC. AND SUBSIDIARIES
	Valuation and Qualifying Accounts and Reserves
	For the Years Ended December 31, 2014, 2013 and 2012
	(In thousands)
			Balance at		Provision for			Other		Bad Debt			Balance at
			Beginning		Bad Debt			Accounts (1)		Write-offs			End of Period
			of Period
	Allowance for doubtful trade receivables:
	Year ended December 31, 2014		$	2,409	$	1,309		$	146	$	(509	)	$	3,355
	Year ended December 31, 2013		$	1,917	$	952			-	$	(460	)	$	2,409
	Year ended December 31, 2012		$	1,651	$	931			-	$	(665	)	$	1,917
			Balance at		Provision for			Other		Bad Debt			Balance at
			Beginning		Credit Losses			Accounts		Write-offs			End of Period
			of Period
	Allowance for doubtful notes receivable:
	Year ended December 31, 2014		$	312	$	42			-	$	(3	)	$	351
	Year ended December 31, 2013		$	291	$	55			-	$	(34	)	$	312
	Year ended December 31, 2012		$	416	$	(48	)		-	$	(77	)	$	291
		-1	Addition to allowance for doubtful accounts following acquisition of Barr-Nunn.

Accounting_Policies_by_Policy_

Accounting Policies, by Policy (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	Principles of Consolidation - The accompanying consolidated financial statements include Knight Transportation, Inc. and its wholly owned and controlled subsidiaries. The Company's non-controlling interests in subsidiaries are not significant. All intercompany accounts and transactions are eliminated upon consolidation.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates - The preparation of financial statements in conformity with United States Generally Accepted Accounting Principles ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements. Estimates and assumptions equally apply to the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents - Cash and cash equivalents are comprised of cash, money market funds, and short-term, 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.
Finance, Loans and Leases Receivable, Policy [Policy Text Block]	Notes Receivable – The Company provides financing to independent contractors and third parties on equipment sold or leased under the Company's equipment sale program. Most of the notes are collateralized and are due in weekly installments, including principal and interest payments, ranging from 2% to 20%. The Company had 109 and 117 loans outstanding from independent contractors and third parties as of December 31, 2014 and 2013, respectively.
	The notes receivable balances are classified separately between current and long-term notes in the consolidated balance sheets. The current and long-term balances of our notes receivables as of December 31, 2014 and 2013 are as follows:
			2014			2013
			(In thousands)
	Notes receivable from independent contractors		$	1,554		$	503
	Notes receivable from third parties			3,882			4,630
	Gross notes receivable			5,436			5,133
	Allowance for doubtful notes receivable			(351	)		(312	)
	Total notes receivable, net of allowance		$	5,085		$	4,821
	Current portion, net of allowance			1,020			774
	Long-term portion		$	4,065		$	4,047
Disclosure of Long Lived Assets Held-for-sale [Table Text Block]	Assets Held for Sale - The Company had $23.2 million and $16.5 million of revenue equipment not being utilized in operations, which is classified as assets held for sale, as of December 31, 2014 and 2013, respectively. Assets held for sale are recorded at the lower of depreciated value or fair market value less selling costs and are not subject to depreciation. The Company periodically reviews the carrying value of these assets for possible impairment. No impairment was recorded in 2014 or 2013. The Company expects to sell these assets within 12 months.
Inventory, Policy [Policy Text Block]	Other Current Assets - Included in other current assets are inventories of tires, spare parts, and fuel.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and Equipment - Property and equipment is stated at cost less accumulated depreciation. Property and equipment is depreciated to estimated salvage values using the straight-line method of depreciation over the following estimated useful lives:
		Years
	Land improvements	5	-	10
	Buildings and improvements	10	-	30
	Furniture and fixtures	3	-	10
	Shop and service equipment	2	-	10
	Revenue equipment	5	-	10
	Leasehold improvements	1	-	5
	The Company expenses repairs and maintenance as incurred. For the years ended December 31, 2014, 2013, and 2012, repairs and maintenance expense totaled approximately $30.9 million, $30.5 million, and $30.4 million, respectively. The expense is included in “Operations and maintenance” expense in the accompanying consolidated statements of income.
	The Company periodically reviews the reasonableness of its estimates regarding useful lives and salvage values for revenue equipment and other long-lived assets based upon, among other things, the Company's experience with similar assets, conditions in the used revenue equipment market, and prevailing industry practice.
	Tires on revenue equipment purchased are capitalized as a part of the equipment cost and depreciated over the life of the vehicle. Replacement tires and recapping costs are expensed when placed in service.
Investment, Policy [Policy Text Block]	Other Long-term Assets and Restricted Cash and Investments include:
			2014			2013
			(In thousands)
	Investment in Transportation Resource Partners (TRP)		$	477		$	2,035
	Investment in Transportation Resource Partners III (TRP III)			5,412			11,440
	Restricted Cash and Investments			3,264			3,603
	Available-For-Sale Equity Securities			26,884			17,454
	Other			1,243			1,662
			$	37,280		$	36,194
	In 2003, the Company signed a partnership agreement with TRP, a company that makes privately negotiated equity investments.  According to the original partnership agreement, the Company committed to invest $5.0 million out of approximately $260.0 million total, for a 1.9% ownership interest. In early 2006, the Company increased the commitment amount to $5.5 million.  Contributions to TRP are accounted for using the cost method as the level of influence over the operations of TRP is minor. In 2014, the Company received distributions totaling $2.1 million from TRP for the sale of TRP portfolio companies. The proceeds from the sale resulted a $1.6 million gain for the Company, with the remaining proceeds representing a return of investment in TRP. The Company also received additional earn-outs of $467,000 and $216,000 in 2013 and 2012, respectively, for disposed portfolios. The earn-outs are recognized as gains in the year received. The Company also recorded impairment of $1.0 million and $209,000 in 2014 and 2013, respectively, for an other-than-temporary loss on the investments remaining within the TRP portfolio. No impairment was recorded in 2012. No contributions have been made to TRP since 2011. The Company's ownership interest in TRP is approximately 1.9%, with a carrying value of $477,000 and $2.0 million at December 31, 2014 and 2013, respectively.
	In the fourth quarter of 2008, the Company committed to invest $15.0 million in a new partnership managed and operated by the managers and principals of TRP. The new partnership, TRP III, focuses on the same investment opportunities as TRP. Since its inception, the Company has contributed approximately $10.9 million to TRP III, leaving an outstanding commitment of $4.1 million as of December 31, 2014. The investment in TRP III is accounted for using the equity method. The Company has recorded income of approximately $6.1 million, $669,000, and $261,000 for its investment in TRP III for years ended December 31, 2014, 2013, and 2012, respectively. In 2014, the Company received distributions totaling $12.3 million from TRP III for the sale of TRP III portfolio companies. At December 31, 2014, the investment balance in TRP III was $5.4 million, compared to $11.4 million at December 31, 2013.  The Company's ownership interest was approximately 6.1% as at December 31, 2014.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Restricted Cash and Investments – In connection with the Company's self-insurance program, $3.3 million and $3.6 million have been set aside in escrow accounts to meet statutory requirements as of December 31, 2014 and 2013, respectively.
	In accordance with the provisions of ASC 210, Balance Sheet, and ASC 320, Investments – Debt and Equity Securities, the Company's investments in debt or equity securities are classified as either trading securities, held-to-maturity securities, or available-for-sale securities, based on the Company's intent with respect to those securities. Investments in debt and equity securities are classified as trading securities if they are held principally for the purpose of selling in the near term. Investments in debt securities are classified as held-to-maturity if the Company has the positive intent to hold such securities to maturity and the ability to do so. Investments in debt and equity securities not classified as trading or held-to-maturity are classified as available-for-sale.
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	Impairment of Long-Lived Assets – ASC 360-10, Property, Plant and Equipment, provides a single accounting model for the assessment of impairment of long-lived assets. In accordance with ASC 360-10, Long-lived Assets, such as property and equipment and purchased intangibles to be held and used in operations, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Long-lived assets are grouped at the lowest level at which identifiable cash flows are largely independent when assessing impairment. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets classified as held for sale are not depreciated and are presented in the Company's consolidated balance sheets at the lower of the carrying amount or fair value less costs to sell. Revenue equipment classified as held for sale is presented in "Assets held for sale" on the Company's consolidated balance sheets. Recoverability of long-lived assets is dependent upon, among other things, the Company's ability to continue to achieve profitability in order to meet its obligations when they become due. In the opinion of management, based upon current information, the carrying amount of long-lived assets will be recovered by future cash flows generated through the use of such assets over their respective estimated useful lives.
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill & Intangibles, net - Goodwill is not amortized, but it is reviewed for impairment at least annually or more frequently should any of the circumstances listed in ASC 350-20, Goodwill, occur. The standard permits an entity to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step impairment test is unnecessary. However, if an entity concludes otherwise, then it is required to perform the impairment test as prescribed in ASC 350-20. Goodwill is required to be tested for impairment at the reporting unit level utilizing a two-step methodology. The initial step requires the Company to determine the fair value of the reporting unit and compare it to the carrying value of such unit, including goodwill. No impairment is recognized if the fair value exceeds the carrying value; however, if the carrying value of the reporting unit exceeds its fair value, the goodwill of the reporting unit may be impaired. The amount, if any, of the impairment would then be measured in the second step. In 2014, the Company changed the date of the annual impairment testing to September 30, from December 31. This change did not result in the delay, acceleration or avoidance of an impairment charge. The Company believes this change in accounting principle is preferable because it better aligns with the Company’s annual strategic and planning process and alleviates administrative burden during the year-end reporting period. This change to the annual goodwill impairment testing was applied prospectively and had no effect on the consolidated financial statements. This change was not applied retrospectively as it is impractical to do so because retrospective application would have required the application of significant estimates and assumptions without use of hindsight. The Company completed this annual test as of both December 31, 2013, and September 30, 2014, and no adjustment for impairment was determined to be necessary. The Company has no accumulated goodwill impairment loss from prior years.
	In conjunction with the acquisition of Roads West in 2006, the basis of goodwill for tax purposes was determined to be in excess of the book basis of goodwill. Under this circumstance, ASC 740, Income Taxes, requires that the goodwill be separated into two components for the acquisitions before the adoption of ASC 805, Business Combination. The first component is equivalent to book goodwill, and future tax amortization of this component is treated as a temporary difference, for which a deferred tax liability is established. The second component is the excess tax goodwill over the book goodwill, for which no deferred taxes are recognized. The tax benefit from the recognition of the amortization of the second component on the tax return is treated as a reduction in the book basis of goodwill. The finite lived intangible portion was amortized using the straight-line method over a five-year period, and was fully amortized as of December 31, 2011.
	The changes in the carrying amounts of goodwill were as follows:
			2014			2013
			(In thousands)
	Goodwill at beginning of period		$	10,257		$	10,276
	Acquisition			36,835			-
	Amortization relating to deferred tax assets			(25	)		(19	)
	Goodwill at end of period		$	47,067		$	10,257
	In conjunction with the acquisition of Barr-Nunn Transportation, Inc. and certain affiliates (“Barr-Nunn”), identifiable intangible assets subject to amortization were recorded at fair value at the acquisition date totaling $3.7 million, and is being amortized over a weighted average amortization period of 7.6 years. Amortization expense associated with these intangible assets from the date of acquisition to December 31, 2014 was $0.1 million and was included in depreciation and amortization in the consolidated statement of income. Future amortization expense for intangible assets is estimated at $0.5 million for 2015 through 2019. The balance of intangible assets in the consolidated balance sheet is $3.6 million at December 31, 2014. The Company did not have any intangible assets subject to amortization as of December 31, 2013.
Claims Accrual [Policy Text Block]	Claims Accrual - The claims reserves represent accruals for estimated pending claims within the self-insured retention ("SIR"), including adverse development of known claims and incurred but not reported claims. These estimates are based on the Company's claims experience, including claims settlement patterns, historical payment trends, the experience/knowledge of the Company's self-administered claims as well as that of the third-party administrator as it relates to workers' compensation claims, along with assumptions about future events. The most significant assumptions used in the estimation process include determining the trend in costs, the expected cost of claims incurred but not reported, and the expected costs to settle or pay outstanding claims. Changes in assumptions and changes in actual experience could cause these estimates to change significantly in the near term. A higher SIR may cause assumptions and estimates to vary more unpredictably than a lower SIR.
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition - The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable, and collectability is probable. These conditions are met upon delivery.
	In accordance with ASC 605-45, Revenue Recognition – Principal Agent Consideration, the Company accounts for revenue from our Trucking operations, our Logistics operations, and revenue on freight transported by independent contractors on a gross basis. The Company is the primary obligor in the arrangements, the Company has the ability to establish prices, the Company has discretion in selecting the independent contractor or other third-party that will perform the service, the Company has the risk of loss in the event of cargo claims, and the Company bears credit risk with customer payments.  Accordingly, all such revenue billed to customers is classified as operating revenue and all corresponding payments to carriers for transportation services the Company arranges in connection with Brokerage and Intermodal activities and to independent contractor providers of revenue equipment are classified as purchased transportation expense.
Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block]	Allowance for Doubtful Accounts - Revenue is recognized when freight is delivered, creating a credit sale and an account receivable. Credit terms for customer accounts are typically on a net 30 day basis. 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. The Company 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. Historically, the Company has not had significant losses related to uncollectible accounts.
	Allowance for Doubtful Notes Receivable - The Company evaluates the collectability of notes and finance lease receivables on a customer-by-customer basis. The Company establishes an allowance for credit losses based on specific customer circumstances, payment patterns, credit risk changes, and historical loss experience. The Company reviews the adequacy of its allowance for doubtful notes receivable quarterly.  Uncollectible accounts are written off when deemed uncollectible, and notes receivable are presented net of an allowance for doubtful accounts. Historically, the Company has not had significant losses related to uncollectible accounts.
Income Tax, Policy [Policy Text Block]	Income Taxes - The Company accounts for income taxes under the asset and liability method. This method requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized as income in the period that includes the enactment date.
	The Company records a valuation allowance for deferred tax assets to the extent it believes these assets are not more likely than not to 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. A valuation allowance for deferred tax assets has not been deemed necessary due to the Company's profitable operations.
	The Company recognizes a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Financial Instruments- The Company's financial instruments include cash equivalents, investments held for trading, available-for-sale securities, trade receivables, notes receivable, accounts payable and long-term debt.  Due to the short-term nature of cash equivalents, trade receivables, and accounts payable, the fair value of these instruments approximates their recorded value.  Available-for-sale and trading securities consist of marketable equity and debt securities stated at fair value. Due to the variable interest rate, the fair value of long-term debt approximates fair value.
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentration of Credit Risk - Financial instruments that potentially subject the Company to credit risk consist principally of trade receivables and notes receivable. Revenue for the Company's three largest customers accounted for approximately 11.7%, 11.0% and 10.0% of the total revenue for the years ended 2014, 2013 and 2012, respectively. As of December 31, 2014, balances due from the three largest customers account for approximately 6.7% of the total trade receivable balance compared to 6.5% as of December 31, 2013. Revenue from the Company's single largest customer represented approximately 4.3% of total revenue for the year ended December 31, 2014, and approximately 4.0% for the years ended 2013, and 2012. The balance due from the single largest customer accounts for approximately 3.2% of the total trade receivable balance as of December 31, 2014, compared to 1.2% as of December 31, 2013.
Earnings Per Share, Policy [Policy Text Block]	Earnings Per Share - A reconciliation of the numerator (net income) and denominator (weighted average number of shares outstanding) of the basic and diluted earnings per share ("EPS") computations for 2014, 2013, and 2012 are as follows (in thousands, except per share data):
			2014								2013						2012
			Net Income (numerator)			Shares (denominator)			Per Share Amount		Net Income (numerator)		Shares (denominator)		Per Share		Net Income (numerator)		Shares (denominator)		Per Share Amount
															Amount
	Basic EPS		$	102,862			80,947		$	1.27	$	69,282		79,994	$	0.87	$	64,117		79,673	$	0.8
	Effect of stock options & restricted stock			-			1,095					-		336				-		327
	Diluted EPS		$	102,862			82,042		$	1.25	$	69,282		80,330	$	0.86	$	64,117		80,000	$	0.8
	Certain shares of options, restricted stock units, and performance restricted stock units (“equity awards”) were excluded from the computation of diluted earnings per share because the equity award’s exercise prices were greater than the average market price of the common shares and the sum total of assumed proceeds resulted in few shares repurchased than the weighted equity awards outstanding hypothetically exercised per the treasury method. A summary of those shares for the years ended December 31, 2014, 2013, and 2012, respectively, is as follows:
			2014			2013			2012
	Number of anti-dilutive shares			232,803			1,917,020			1,926,298
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Pronouncements
	In June 2014, the FASB issued ASU 2014-12, Stock Compensation - Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. The amendments in this update require performance targets that could be achieved after the requisite service period be treated as performance conditions that affect the vesting of the award. The amendment is effective as of January 1, 2016 and we do not expect it to have an impact on our consolidated financial statements.
	In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers. The main objective of this update is to require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. The guidance in this update supersedes virtually all present U.S. GAAP guidance on revenue recognition. The amendments to the standard require the use of more estimates and judgments than the present standards and require additional disclosures. The amendments are effective as of January 1, 2017 and we are currently evaluating this standard and our existing revenue recognition policies to determine which of our customer arrangements in the scope of the guidance will be affected by the new requirements and what impact they would have on our consolidated financial statements upon adoption of this standard.

Note_1_Organization_and_Summar1

Note 1 - Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]			2014			2013
			(In thousands)
	Notes receivable from independent contractors		$	1,554		$	503
	Notes receivable from third parties			3,882			4,630
	Gross notes receivable			5,436			5,133
	Allowance for doubtful notes receivable			(351	)		(312	)
	Total notes receivable, net of allowance		$	5,085		$	4,821
	Current portion, net of allowance			1,020			774
	Long-term portion		$	4,065		$	4,047
Schedule of Estimated Useful Lives [Table Text Block]		Years
	Land improvements	5	-	10
	Buildings and improvements	10	-	30
	Furniture and fixtures	3	-	10
	Shop and service equipment	2	-	10
	Revenue equipment	5	-	10
	Leasehold improvements	1	-	5
Schedule of Other Assets [Table Text Block]			2014			2013
			(In thousands)
	Investment in Transportation Resource Partners (TRP)		$	477		$	2,035
	Investment in Transportation Resource Partners III (TRP III)			5,412			11,440
	Restricted Cash and Investments			3,264			3,603
	Available-For-Sale Equity Securities			26,884			17,454
	Other			1,243			1,662
			$	37,280		$	36,194
Schedule of Goodwill [Table Text Block]			2014			2013
			(In thousands)
	Goodwill at beginning of period		$	10,257		$	10,276
	Acquisition			36,835			-
	Amortization relating to deferred tax assets			(25	)		(19	)
	Goodwill at end of period		$	47,067		$	10,257
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]			2014								2013						2012
			Net Income (numerator)			Shares (denominator)			Per Share Amount		Net Income (numerator)		Shares (denominator)		Per Share		Net Income (numerator)		Shares (denominator)		Per Share Amount
															Amount
	Basic EPS		$	102,862			80,947		$	1.27	$	69,282		79,994	$	0.87	$	64,117		79,673	$	0.8
	Effect of stock options & restricted stock			-			1,095					-		336				-		327
	Diluted EPS		$	102,862			82,042		$	1.25	$	69,282		80,330	$	0.86	$	64,117		80,000	$	0.8
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]			2014			2013			2012
	Number of anti-dilutive shares			232,803			1,917,020			1,926,298
Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]			31-Dec-13
			(in thousands)
	Account		As Previously			Adjustment			As Adjusted
			Reported
	Accrued liabilities(1)		$	18,800		$	262		$	19,062
	Total current liabilities			62,802			262			63,064
	Deferred tax liability			142,504			(2,355	)		140,149
	Total long term liabilities			191,879			(2,355	)		189,524
	Total liabilities			254,681			(2,093	)		252,588
	Additional paid-in capital			150,079			779			150,858
	Retained earnings			396,032			1,314			397,346
	Total Knight Transportation shareholders’ equity			551,495			2,093			553,588
	Total shareholders' equity			552,440			2,093			554,533

Note_2_Fair_Value_Measurements1

Note 2 - Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements, Nonrecurring [Table Text Block]						Level One				Level Two				Level Three
		Balance at		Balance at		Balance at		Balance at		Balance at		Balance at		Balance at		Balance at
		31-Dec-14		31-Dec-13		31-Dec-14		31-Dec-13		31-Dec-14		31-Dec-13		31-Dec-14		31-Dec-13
		(In thousands)
	Assets:
	Available-for-sale Securities:
	Equity securities - common shares	$	26,884	$	17,454	$	26,884	$	17,454		-		-		-		-
	Restricted cash and investments:
	Money market funds	$	1,027	$	1,371	$	1,027	$	1,371		-		-		-		-
	Trading Securities:
	Debt securities - municipal securities	$	2,237	$	2,232		-		-	$	2,237	$	2,232		-		-
Schedule of Realized Gain (Loss) [Table Text Block]		December 31,
		2014		2013		2012
		(in thousands)
	Sales proceeds	$	6,355	$	8,782	$	112
	Cost of securities sold		3,190		6,857		51
	Realized gain	$	3,165	$	1,925	$	61
	Realized gains, net of taxes	$	1,932	$	1,189	$	38

Note_4_Income_Taxes_Tables

Note 4 - Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]		2014			2013			2012
	Current income taxes:
	Federal	$	42,101		$	46,445		$	42,280
	State		8,648			5,573			4,709
			50,749			52,018			46,989
	Deferred income taxes:
	Federal		12,644			(5,520	)		(2,403	)
	State		4,416			182			428
			17,060			(5,338	)		(1,975	)
		$	67,809		$	46,680		$	45,014
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]		2014			2013			2012
	Tax at the statutory rate (35%)	$	60,141		$	40,846		$	38,422
	State income taxes, net of federal benefit		8,492			3,804			3,489
	Nondeductible driver per diem		1,885			1,807			1,989
	Other, net		(2,709	)		223			1,114
		$	67,809		$	46,680		$	45,014
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]		2014			2013
	Short-term deferred tax assets (liabilities):
	Claims accrual	$	6,322		$	2,460
	Stock options		-			2,254
	Investments		(2,066	)		-
	Prepaid expenses deducted for tax purposes		(2,952	)		(2,237	)
	Other, net		1,883			882
	Short-term deferred tax assets, net	$	3,187		$	3,359
	Long-term deferred tax liabilities (assets):
	Property and equipment depreciation	$	161,209		$	143,488
	Claims accrual		(4,482	)		(984	)
	Stock options		(2,847	)		-
	Investments		7,807			-
	Other, net		320			-
	Long-term deferred liabilities, net	$	162,007		$	142,504

Note_5_Commitments_and_Conting1

Note 5 - Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Year Ending	Amount
	December 31,	(In thousands)
	2015	$	2,928
	2016		2,679
	2017		2,699
	2018		1,362
	Total	$	9,668

Note_6_Claims_Accrual_Tables

Note 6 - Claims Accrual (Tables)	12 Months Ended
	Dec. 31, 2014
Claims Accrual [Abstract]
Schedule of Accrued Liabilities [Table Text Block]		2014			2013
		(In thousands)
	Auto reserves	$	18,075		$	15,432
	Workers' compensation reserves		8,728			6,479
	Employee medical reserves		3,234			2,594
	Total reserves	$	30,037		$	24,505
	Current portion	$	18,532		$	15,616
	Long-term portion	$	11,505		$	8,889
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]		2014			2013
		(In thousands)
	Beginning Balance	$	24,505		$	26,232
	Acquisition (1)		3,209			-
	Provisions recorded		49,135			43,797
	Claims paid and direct expenses		(46,812	)		(45,524	)
	Total reserves	$	30,037		$	24,505

Note_8_Shareholders_Equity_Tab

Note 8 - Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
Schedule of Share-based Compensation, Nonemployee Director Stock Award Plan, Activity [Table Text Block]		2014		2013		2012
	Annual director fees paid through stock issuance	$	200,484	$	167,946	$	148,437
	Shares of common stock issued		8,828		9,885		9,040
	Dividends paid per common share	$	0.24	$	0.24	$	0.74

Note_9_Stockbased_Compensation1

Note 9 - Stock-based Compensation and Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Note 9 - Stock-based Compensation and Employee Benefit Plans (Tables) [Line Items]
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]			2014								2013								2012
			Options				Weighted				Options				Weighted				Options				Weighted
							Average								Average								Average
							Exercise								Exercise								Exercise
							Price								Price								Price
	Outstanding at beginning of year			3,374,846			$	16.26				3,424,806			$	15.99				3,823,585			$	15.8
	Granted			399,550				22.74				429,800				15.62				-			$	0
	Exercised			(1,551,400	)			15.73				(345,302	)			12.6				(281,993	)		$	12.85
	Forfeited and Expired			(80,025	)			17.9				(134,458	)			16.78				(116,786	)		$	17.13
	Outstanding at end of year			2,142,971				17.8				3,374,846				16.26				3,424,806			$	15.99
	Vested and exercisable at end of year			1,383,888				16.86				2,828,365				16.27				3,174,843			$	15.86
	Weighted average fair value of options granted during the period							3.96								2.25							N/A
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]	Range of				Shares				Weighted Avg.				Weighted Avg.				Number Vested				Weighted
	Exercise				Outstanding				Contractual				Exercise Price				and Exercisable				Avg. Exercise
	Prices								Years				Per Share								Price Per
									Remaining												Share for
																					Vested and
																					Exercisable
	$12.63	-	14.73			54,995				0.58			$	14.4				52,395			$	14.45
	$14.74	-	16.83			834,187				2.62			$	15.41				540,854			$	15.32
	$16.84	-	18.94			854,289				2.9			$	18.1				770,889			$	18.01
	$18.95	-	33.27			399,500				4.1			$	22.6				19,750			$	20.21
	Overall Total					2,142,971				2.95			$	17.8				1,383,888			$	16.86
Stock Compensation Plan [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Tables) [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]			Year Ended December 31,
			2014				2013			2012
	Dividend yield (1)			1.06	%			1.54	%	N/A
	Expected volatility (2)			28.01	%			24.92	%	N/A
	Risk-free interest rate (3)			0.82	%			0.34	%	N/A
	Expected terms (years) (4)			2.74				2.74		N/A
	Weighted average fair value of options granted		$	3.96			$	2.25		N/A
Restricted Stock Units (RSUs) [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Tables) [Line Items]
Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]			2014								2013								2012
			Number of				Weighted				Number of				Weighted				Number of				Weighted
			Restricted				Average				Restricted				Average				Restricted				Average
			Stock Awards				Grant Date				Stock Awards				Grant Date				Stock Awards				Grant Date
							Fair Value								Fair Value								Fair Value
	Unvested at January 1
	Unvested at January1,			1,213,698			$	16.04				1,210,532			$	16.04				1,325,817			$	16.01
	Granted			17,017			$	27.63				183,111			$	15.95				41,000			$	16.76
	Vested			(128,659	)		$	16.07				(130,265	)		$	16.01				(114,605	)		$	16
	Forfeited and Expired			(28,510	)		$	16.23				(49,680	)		$	15.75				(41,680	)		$	15.97
	Outstanding (unvested) at end of year			1,073,546			$	16.22				1,213,698			$	16.04				1,210,532			$	16.04
Performance Shares [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Tables) [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]			Year Ended December 31, 2014
	Dividend yield (1)			1.06	%
	Expected volatility (2)			26.11	%
	Average peer volatility(2)			36.01	%
	Average peer correlation coefficient(3)			0.5796
	Risk-free interest rate (4)			0.66	%
	Expected term (5)			2.8
	Weighted average fair value of PRSUs granted		$	23.85

Note_11_Segment_Information_Ta

Note 11 - Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Note 11 - Segment Information (Tables) [Line Items]
Reconciliation of Revenue from Segments to Consolidated [Table Text Block]		2014								2013						2012
	Revenues:	$				%				$			%			$			%
	Trucking Segment	$	892,124				80.9	%		$	822,188			84.8	%	$	836,357			89.3	%
	Logistics Segment		214,378				19.4				151,194			15.6			105,794			11.3
	Subtotal		1,106,502								973,382						942,151
	Intersegment Eliminations Trucking		(65	)			0				(120	)		0			(112	)		0
	Intersegment Eliminations Logistics		(4,105	)			(0.3	)			(4,025	)		(0.4	)		(6,003	)		(0.6	)
	Total	$	1,102,332				100	%		$	969,237			100	%	$	936,036			100	%
	Operating Income:
	Trucking Segment	$	147,424				90.6	%		$	106,167			93.2	%	$	103,013			95.1	%
	Logistics Segment		15,298				9.4				7,742			6.8			5,254			4.9
	Total	$	162,722				100	%		$	113,909			100	%	$	108,267			100	%
Trucking (Asset-Based) Segment [Member]
Note 11 - Segment Information (Tables) [Line Items]
Reconciliation of Revenue from Segments to Consolidated [Table Text Block]	GAAP Presentation:	2014								2013						2012
	Trucking (amounts in thousands)	$				%				$			%			$			%
	Revenue	$	892,124							$	822,188					$	836,357
	Operating expenses		744,700				83.5				716,021			87.1			733,344			87.7
	Operating income	$	147,424							$	106,167					$	103,013
	Non-GAAP Presentation(1):	2014								2013						2012
	Trucking (amounts in thousands)	$				%				$			%			$			%
	Revenue	$	892,124							$	822,188					$	836,357
	Less: Trucking fuel surcharge revenue		(176,347	)							(177,386	)					(183,885	)
	Less: Intersegment transactions		(65	)							(120	)					(112	)
	Revenue, net of fuel surcharge and intersegment transactions		715,712								644,682						652,360
	Operating expenses		744,700								716,021						733,344
	Less: Trucking fuel surcharge revenue		(176,347	)							(177,386	)					(183,885	)
	Less: Intersegment transactions		(65	)							(120	)					(112	)
	Operating expenses, net of fuel surcharge and intersegment transactions		568,288				79.4				538,515			83.5			549,347			84.2
	Operating income	$	147,424							$	106,167					$	103,013
Logistics (Non-Asset-Based) Segment [Member]
Note 11 - Segment Information (Tables) [Line Items]
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]		2014								2013						2012
	Logistics (amounts in thousands)	$				%				$			%			$			%
	Revenue	$	214,378							$	151,194					$	105,794
	Other operating expense		199,080				92.9				143,452			94.9			100,540			95
	Operating income	$	15,298							$	7,742					$	5,254
		2014								2013						2012
	Logistics (amounts in thousands)	$				%				$			%			$			%
	Revenue	$	214,378							$	151,194					$	105,794
	Less: Intersegment transactions		(4,105	)							(4,025	)					(6,003	)
	Revenue excluding intersegment transactions		210,273								147,169						99,791
	Operating expenses		199,080								143,452						100,540
	Less: Intersegment transactions		(4,105	)							(4,025	)					(6,003	)
	Operating expenses excluding intersegment transactions		194,975				92.7				139,427			94.7			94,537			94.7
	Operating income	$	15,298							$	7,742					$	5,254
Schedule of Segment Reporting Information, by Segment [Table Text Block]				2014					2013				2012
	Combined Brokerage and Intermodal gross margin percent (1)				15	%				12.5	%			13.2	%

Note_12_Acquisition_of_BarrNun1

Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Acquisition, Pro Forma Information [Table Text Block]		(Unaudited)
		Years ended
		December 31,			December 31,		December 31,
		2014			2013		2012
		(in thousands)
	Total revenue	$	1,192,745		$	1,087,790	$	1,052,711
	Net income		109,787			78,274		72,376
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	ALLOCATION OF PURCHASE PRICE	(in thousands)
	Total fair value of consideration transferred	$	110,517
	Allocated to:
	Historical book value of Barr-Nunn’s assets and liabilities (excluding cash)	$	71,656
	Adjustments to recognize assets and liabilities at acquisition-date fair value:
	Property, and equipment		3,349
	Liabilities		-5,023
	Fair value of tangible net assets acquired		69,982
	Identifiable intangibles at acquisition-date fair value		3,700
	Excess of consideration transferred over the net amount of assets and liabilities recognized, including $3.5 million attributable to the fair value of a potential earn-out obligation (goodwill)	$	36,835
		(in thousands)
	Trade receivables	$	11,380
	Other current assets		2,316
	Property and equipment		68,444
	Goodwill		36,835
	Intangible assets		3,700
	Total assets		122,675
	Accounts payable		(3,311	)
	Accrued liabilities		(5,638	)
	Claims accruals		(3,209	)
	Total consideration transferred	$	110,517
	Cash paid pursuant to Stock Purchase and Real Estate Agreements	$	110,517

Note_13_Quarterly_Financial_Da1

Note 13 - Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]		2014
		31-Mar		30-Jun		30-Sep		31-Dec
	Revenue, before fuel surcharge		205,596		218,908		227,829		273,653
	Income from operations		31,250		38,899		39,791		52,782
	Net income attributable to Knight		19,064		25,761		25,100		32,938
	Earnings per common share:
	Basic	$	0.24	$	0.32	$	0.31	$	0.4
	Diluted	$	0.23	$	0.31	$	0.31	$	0.4
		2013
		31-Mar		30-Jun		30-Sep		31-Dec
	Revenue, before fuel surcharge		189,600		200,104		195,847		206,300
	Income from operations		25,544		31,925		24,274		32,165
	Net income attributable to Knight		15,183		18,939		15,059		20,101
	Earnings per common share:
	Basic	$	0.19	$	0.24	$	0.19	$	0.25
	Diluted	$	0.19	$	0.24	$	0.19	$	0.25

Note_1_Organization_and_Summar2

Note 1 - Organization and Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended				72 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2006	Dec. 31, 2008
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Number of Reportable Segments	2
Interest On Note Receivable Minimum	2.00%
Interest On Note Receivable Maximum	20.00%
Loans Outstanding Independent Contractors	109	117			109	109
Disposal Group, Including Discontinued Operation, Long Lived Assets, Noncurrent	$23,200,000	$16,500,000			$23,200,000	$23,200,000
Cost of Property Repairs and Maintenance	30,900,000	30,500,000		30,400,000
Other than Temporary Impairment Losses, Investments	1,041,000	209,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	500,000				500,000	500,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	500,000				500,000	500,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	500,000				500,000	500,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	500,000				500,000	500,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	500,000				500,000	500,000
Intangible Assets, Net (Excluding Goodwill)	3,575,000	0			3,575,000	3,575,000
Deferred Tax Liabilities, Net, Noncurrent	162,007,000	140,149,000			162,007,000	162,007,000
Accrued Liabilities, Current	20,604,000	19,062,000	[1]		20,604,000	20,604,000
Additional Paid in Capital, Common Stock	185,184,000	150,858,000			185,184,000	185,184,000
Retained Earnings (Accumulated Deficit)	479,527,000	397,346,000			479,527,000	479,527,000
Self Insurance Program [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Restricted Cash and Cash Equivalents	3,300,000	3,600,000			3,300,000	3,300,000
Three Largest Customers [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Concentration Risk, Percentage	11.70%	11.00%		10.00%
Three Largest Customers [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Concentration Risk, Percentage	6.70%	6.50%
Single Largest Customer [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Concentration Risk, Percentage	4.30%	4.00%		4.00%
Single Largest Customer [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Concentration Risk, Percentage	1.20%	3.20%
Scenario, Adjustment [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Deferred Tax Liabilities, Net, Noncurrent		-2,355,000					-2,355,000
Accrued Liabilities, Current		262,000	[1]				262,000
Additional Paid in Capital, Common Stock		779,000					779,000
Retained Earnings (Accumulated Deficit)		1,314,000					1,314,000
Transportation Resource Partners [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		5,000,000
Total Amounts Committed To Partnership		260,000,000
Joint Venture Ownership Interest		1.90%
Amounts Committed To Invest	5,500,000				5,500,000	5,500,000		5,500,000
Payments for (Proceeds from) Investments	-2,100,000
Gain on Sale of Investments	1,600,000	467,000		216,000
Other than Temporary Impairment Losses, Investments	1,000,000	209,000
Investments	477,000	2,000,000			477,000	477,000
Transportation Resource Partners III [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Amounts Committed To Invest	15,000,000				15,000,000	15,000,000			15,000,000
Payments for (Proceeds from) Investments	-12,300,000				10,900,000
Investments	10,900,000				10,900,000	10,900,000
Remaining Investment Commitment	4,100,000				4,100,000	4,100,000
Income (Loss) from Equity Method Investments	6,100,000	669,000		261,000
Equity Method Investments	5,412,000	11,440,000			5,412,000	5,412,000
Equity Method Investment, Ownership Percentage	6.10%				6.10%	6.10%
Barr-Nunn Transportation, Inc [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	3,700,000				3,700,000	3,700,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life						7 years 219 days
Amortization of Intangible Assets						$100,000
[1]	Income tax payable is included in Accrued Liabilities of our consolidated balance sheets.

Note_1_Organization_and_Summar3

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Current and Long-term Balance of Notes Receivable (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current and Long-term Balance of Notes Receivable [Abstract]
Notes receivable from independent contractors	$1,554	$503
Notes receivable from third parties	3,882	4,630
Gross notes receivable	5,436	5,133
Allowance for doubtful notes receivable	-351	-312
Total notes receivable, net of allowance	5,085	4,821
Current portion, net of allowance	1,020	774
Long-term portion	$4,065	$4,047

Note_1_Organization_and_Summar4

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment	12 Months Ended
	Dec. 31, 2014
Land Improvements [Member] | Minimum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	5 years
Land Improvements [Member] | Maximum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	10 years
Building and Building Improvements [Member] | Minimum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	10 years
Building and Building Improvements [Member] | Maximum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	30 years
Furniture and Fixtures [Member] | Minimum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	10 years
Shopand Service Equipment [Member] | Minimum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	2 years
Shopand Service Equipment [Member] | Maximum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	10 years
Revenue Equipment [Member] | Minimum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	5 years
Revenue Equipment [Member] | Maximum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	10 years
Leasehold Improvements [Member] | Minimum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	1 year
Leasehold Improvements [Member] | Maximum [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Estimated Useful Lives of Property and Equipment [Line Items]
Useful life	5 years

Note_1_Organization_and_Summar5

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Other Long-term Assets and Restricted Cash (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Other Long-term Assets and Restricted Cash [Line Items]
Restricted Cash and Investments	$3,264	$3,603
Available-For-Sale Equity Securities	26,884	17,454
Other	1,243	1,662
	37,280	36,194
Transportation Resource Partners [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Other Long-term Assets and Restricted Cash [Line Items]
Investment in Transportation Resource Partners (TRP)	477	2,035
Transportation Resource Partners III [Member]
Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Other Long-term Assets and Restricted Cash [Line Items]
Investment in Transportation Resource Partners III (TRP III)	$5,412	$11,440

Note_1_Organization_and_Summar6

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Changes in Carrying Amount of Goodwill (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Changes in Carrying Amount of Goodwill [Abstract]
Goodwill at beginning of period	$10,257	$10,276
Acquisition	36,835
Amortization relating to deferred tax assets	-25	-19
Goodwill at end of period	$47,067	$10,257

Note_1_Organization_and_Summar7

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Earnings Per Share (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Basic EPS (in Dollars)									$102,862	$69,282	$64,117
Basic EPS									80,947	79,994	79,673
Basic EPS (in Dollars per share)	$0.40	$0.31	$0.32	$0.24	$0.25	$0.19	$0.24	$0.19	$1.27	$0.87	$0.80
Effect of stock options & restricted stock									1,095	336	327
Diluted EPS (in Dollars)									$102,862	$69,282	$64,117
Diluted EPS									82,042	80,330	80,000
Diluted EPS (in Dollars per share)	$0.40	$0.31	$0.31	$0.23	$0.25	$0.19	$0.24	$0.19	$1.25	$0.86	$0.80

Note_1_Organization_and_Summar8

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Anti-dilutive Shares	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Anti-dilutive Shares [Abstract]
Number of anti-dilutive shares	232,803	1,917,020	1,926,298

Note_1_Organization_and_Summar9

Note 1 - Organization and Summary of Significant Accounting Policies (Details) - Reconciliation of Effects of Adjustments to Previously Reported Balance Sheet (USD $)	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2014
Accrued liabilities(1)	$20,604,000	$19,062,000	[1]
Total current liabilities	92,585,000	63,064,000
Deferred tax liability	162,007,000	140,149,000
Total long term liabilities	310,425,000	189,524,000
Total liabilities	403,010,000	252,588,000
Additional paid-in capital	185,184,000	150,858,000
Retained earnings	479,527,000	397,346,000
Total Knight Transportation shareholders’ equity	677,760,000	553,588,000
Total shareholders' equity	679,275,000	554,533,000		492,933,000	478,843,000
Scenario, Previously Reported [Member]
Accrued liabilities(1)		18,800,000	[1]
Total current liabilities		62,802,000
Deferred tax liability		142,504,000
Total long term liabilities		191,879,000
Total liabilities		254,681,000
Additional paid-in capital		150,079,000
Retained earnings		396,032,000
Total Knight Transportation shareholders’ equity		551,495,000
Total shareholders' equity		552,440,000
Scenario, Adjustment [Member]
Accrued liabilities(1)		262,000	[1]			262,000
Total current liabilities		262,000
Deferred tax liability		-2,355,000				-2,355,000
Total long term liabilities		-2,355,000
Total liabilities		-2,093,000
Additional paid-in capital		779,000				779,000
Retained earnings		1,314,000				1,314,000
Total Knight Transportation shareholders’ equity		2,093,000
Total shareholders' equity		$2,093,000
[1]	Income tax payable is included in Accrued Liabilities of our consolidated balance sheets.

Note_2_Fair_Value_Measurements2

Note 2 - Fair Value Measurements (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value Disclosures [Abstract]
Available-for-sale Securities	$26.90	$17.50
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	20	7.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), Net of Tax	12.2	4.6
Available-for-sale Securities, Amortized Cost Basis	$6.90	$10.10

Note_2_Fair_Value_Measurements3

Note 2 - Fair Value Measurements (Details) - Fair Value of Financial Assets and Liabilities (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets:
Equity securities - common shares	$26,884	$17,454
Restricted cash and investments:
Money market funds	1,027	1,371
Debt securities - municipal securities	2,237	2,232
Fair Value, Inputs, Level 1 [Member]
Assets:
Equity securities - common shares	26,884	17,454
Restricted cash and investments:
Money market funds	1,027	1,371
Fair Value, Inputs, Level 2 [Member]
Restricted cash and investments:
Debt securities - municipal securities	$2,237	$2,232

Note_2_Fair_Value_Measurements4

Note 2 - Fair Value Measurements (Details) - Realized Gains on Available-for-Sale Securities (Other Income [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Income [Member]
Note 2 - Fair Value Measurements (Details) - Realized Gains on Available-for-Sale Securities [Line Items]
Sales proceeds	$6,355	$8,782	$112
Cost of securities sold	3,190	6,857	51
Realized gain	3,165	1,925	61
Realized gains, net of taxes	$1,932	$1,189	$38

Note_3_Line_of_Credit_and_Long1

Note 3 - Line of Credit and Long-term Debt (Details) (USD $)	9 Months Ended	14 Months Ended	12 Months Ended		0 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Oct. 02, 2014	Oct. 21, 2013
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Note 3 - Line of Credit and Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.63%
Line of Credit Facility, Interest Rate During Period		0.75%
Revolving Credit Facility [Member] | Unused Portion Fees [Member]
Note 3 - Line of Credit and Long-term Debt (Details) [Line Items]
Line of Credit Facility, Interest Rate During Period			1.31%	1.04%
Revolving Credit Facility [Member]
Note 3 - Line of Credit and Long-term Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	150					$300
Line of Credit Facility, Interest Rate During Period			0.91%	0.84%
Long-term Line of Credit		134.4	134.4	38
Line of Credit Facility, Remaining Borrowing Capacity		141.3	141.3
Proceeds from Lines of Credit					112
Letter of Credit [Member]
Note 3 - Line of Credit and Long-term Debt (Details) [Line Items]
Long-term Line of Credit		24.3	24.3

Note_4_Income_Taxes_Details

Note 4 - Income Taxes (Details)	12 Months Ended
	Dec. 31, 2014
Earliest Tax Year [Member] | Domestic Tax Authority [Member]
Note 4 - Income Taxes (Details) [Line Items]
Open Tax Year	2011
Earliest Tax Year [Member] | State and Local Jurisdiction [Member]
Note 4 - Income Taxes (Details) [Line Items]
Open Tax Year	2010
Latest Tax Year [Member] | Domestic Tax Authority [Member]
Note 4 - Income Taxes (Details) [Line Items]
Open Tax Year	2014
Latest Tax Year [Member] | State and Local Jurisdiction [Member]
Note 4 - Income Taxes (Details) [Line Items]
Open Tax Year	2014

Note_4_Income_Taxes_Details_In

Note 4 - Income Taxes (Details) - Income Tax Expense (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current income taxes:
Federal	$42,101	$46,445	$42,280
State	8,648	5,573	4,709
	50,749	52,018	46,989
Deferred income taxes:
Federal	12,644	-5,520	-2,403
State	4,416	182	428
	17,060	-5,338	-1,975
	$67,809	$46,680	$45,014

Note_4_Income_Taxes_Details_Ef

Note 4 - Income Taxes (Details) - Effective Income Tax Rate Reconciliation (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation [Abstract]
Tax at the statutory rate (35%)	$60,141	$40,846	$38,422
State income taxes, net of federal benefit	8,492	3,804	3,489
Nondeductible driver per diem	1,885	1,807	1,989
Other, net	-2,709	223	1,114
	$67,809	$46,680	$45,014

Note_4_Income_Taxes_Details_Ef1

Note 4 - Income Taxes (Details) - Effective Income Tax Rate Reconciliation (Parentheticals)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation [Abstract]
Statutory rate	35.00%	35.00%	35.00%

Note_4_Income_Taxes_Details_De

Note 4 - Income Taxes (Details) - Deferred Tax Assets and Deferred Tax Liabilities (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Short-term deferred tax assets (liabilities):
Short-term deferred tax assets, net	$3,187	$3,359
Long-term deferred tax liabilities (assets):
Long-term deferred liabilities, net	162,007	142,504
Deferred Tax Assets (Liabilities), Current [Member]
Short-term deferred tax assets (liabilities):
Claims accrual	6,322	2,460
Stock options		2,254
Investments	-2,066
Prepaid expenses deducted for tax purposes	-2,952	-2,237
Other, net	1,883	882
Long-term deferred tax liabilities (assets):
Claims accrual	-6,322	-2,460
Stock options		-2,254
Investments	2,066
Deferred Tax Liabilities (Assets), Noncurrent [Member]
Short-term deferred tax assets (liabilities):
Claims accrual	4,482	984
Stock options	2,847
Investments	-7,807
Long-term deferred tax liabilities (assets):
Property and equipment depreciation	161,209	143,488
Claims accrual	-4,482	-984
Stock options	-2,847
Investments	7,807
Other, net	$320

Note_5_Commitments_and_Conting2

Note 5 - Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2006	Dec. 31, 2008
Note 5 - Commitments and Contingencies (Details) [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$191,300,000	$12,800,000
Operating Leases, Rent Expense	2,800,000	2,200,000	2,400,000
Transportation Resource Partners [Member]
Note 5 - Commitments and Contingencies (Details) [Line Items]
Amounts Committed To Invest	5,500,000			5,500,000
Investments	477,000	2,000,000
Transportation Resource Partners III [Member]
Note 5 - Commitments and Contingencies (Details) [Line Items]
Amounts Committed To Invest	15,000,000				15,000,000
Investments	10,900,000
Remaining Investment Commitment	$4,100,000

Note_5_Commitments_and_Conting3

Note 5 - Commitments and Contingencies (Details) - Future Minimum Lease Payments (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Future Minimum Lease Payments [Abstract]
2015	$2,928
2016	2,679
2017	2,699
2018	1,362
Total	$9,668

Note_6_Claims_Accrual_Details

Note 6 - Claims Accrual (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Note 6 - Claims Accrual (Details) [Line Items]
Self-Insurance Retention for Workers' Compensation Claims Per Occurrence	$500,000
Excess Personal Injury And Property Damage Liability Insurance	105,000,000
Insurance Aggregate Deductible Amount	2,500,000
Self Retention For Employee Medical Health	225,000	225,000
Operating Insurance and Claims Costs, Production	31,133,000	29,350,000	32,138,000
Current Policy Year [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Self Insurance Retention	3,000,000
Next Policy Year [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Self Insurance Retention	2,500,000
Insurance And Claim Expense [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Operating Insurance and Claims Costs, Production	30,900,000	29,100,000
Workers Compensation Expense [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Increase (Decrease) in Self Insurance Reserve	7,800,000	5,500,000
Medical Expense [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Increase (Decrease) in Self Insurance Reserve	10,400,000	9,200,000
Minimum [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Self Insurance Retention	1,000,000
Maximum [Member]
Note 6 - Claims Accrual (Details) [Line Items]
Self Insurance Retention	3,000,000
Self Insurance Aggregate Losses	$1,500,000

Note_6_Claims_Accrual_Details_

Note 6 - Claims Accrual (Details) - Current and Long-term Claim Reserves (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Note 6 - Claims Accrual (Details) - Current and Long-term Claim Reserves [Line Items]
Reserves	$30,037	$24,505	$26,232
Current portion	18,532	15,616
Long-term portion	11,505	8,889
Auto Reserves [Member]
Note 6 - Claims Accrual (Details) - Current and Long-term Claim Reserves [Line Items]
Reserves	18,075	15,432
Workers Compensation Reserves [Member]
Note 6 - Claims Accrual (Details) - Current and Long-term Claim Reserves [Line Items]
Reserves	8,728	6,479
Employee Medical Reserves [Member]
Note 6 - Claims Accrual (Details) - Current and Long-term Claim Reserves [Line Items]
Reserves	$3,234	$2,594

Note_6_Claims_Accrual_Details_1

Note 6 - Claims Accrual (Details) - Reconciliation of Claim Reserves (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense [Line Items]
Beginning Balance	$24,505		$26,232
Provisions recorded	49,135		43,797
Claims paid and direct expenses	-46,812		-45,524
Total reserves	30,037		24,505
Barr-Nunn Transportation, Inc [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Acquisition (1)	3,209	[1]		[1]
Total reserves	$3,209
[1]	Addition to claims reserve following acquisition of Barr-Nunn.

Note_7_Related_Party_Transacti1

Note 7 - Related Party Transactions (Details) (US West Agriculture Exporters LLC [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
US West Agriculture Exporters LLC [Member]
Note 7 - Related Party Transactions (Details) [Line Items]
Related Party Transaction Percent of Ownership	33.00%
Related Party Transaction, Due from (to) Related Party, Noncurrent		$748,000

Note_8_Shareholders_Equity_Det

Note 8 - Shareholders' Equity (Details) - Annual Director Fees (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Annual Director Fees [Abstract]
Annual director fees paid through stock issuance	$200,484	$167,946	$148,437
Shares of common stock issued	8,828	9,885	9,040
Dividends paid per common share	$0.24	$0.24	$0.74

Note_9_Stockbased_Compensation2

Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee (in Shares)	650,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	4,000,000
Allocated Share-based Compensation Expense	$4,500,000	$2,800,000	$6,300,000
Proceeds from Stock Options Exercised	24,366,000	4,345,000	3,623,000
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	5,300,000	0	30,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	1,900,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in Shares)	2,083,959
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price (in Dollars per share)	$17.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	2 years 328 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	33,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	17,800,000	1,500,000	1,300,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	34,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	23,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	2 years 109 days
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount	1,000
Defined Contribution Plan, Employer Discretionary Contribution Amount	451,000	326,000	266,000
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$22.61	$15.62
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	13 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$33.27	$17.87
Restricted Stock Units (RSUs) [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in Shares)	17,017	183,111	41,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$27.63	$15.95	$16.76
Restricted Stock [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	13,600,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	4 years
Performance Shares [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	3 years 36 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in Shares)	181,112
Share-based Compensation Arrangement by Share-based Payment Award, Payout Range, Lower Limit	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Payout Range, Upper Limit	150.00%
Share-based Compensation Arrangement by Share-based Payment Award, Payout Modifier Range, Lower Limit	75.00%
Share-based Compensation Arrangement by Share-based Payment Award, Payout Modifier Range, Upper Limit	125.00%
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	3,400,000
Pre-Tax [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost			4,000,000
After Tax [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost			3,900,000
Scenario, Forecast [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount				1,150
Weighted Average [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 328 days
Maximum [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount		$850
Reserved For Issuance To Outside Directors [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	200,000

Note_9_Stockbased_Compensation3

Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Fair Value Assumptions - Stock Options (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Fair Value Assumptions - Stock Options [Line Items]
Weighted average fair value of options granted (in Dollars per share)	$3.96		$2.25
Stock Compensation Plan [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Fair Value Assumptions - Stock Options [Line Items]
Dividend yield (1)	1.06%	[1]	1.54%	[1]		[1]
Expected volatility (2)	28.01%	[2]	24.92%	[2]		[2]
Risk-free interest rate (3)	0.82%	[3]	0.34%	[3]		[3]
Expected terms (years) (4)	2 years 270 days	[4]	2 years 270 days	[4]		[4]
Weighted average fair value of options granted (in Dollars per share)	$3.96		$2.25
[1]	The dividend yield is based on the Company's historical experience and future expectation of dividend payouts.
[2]	The Company analyzed the volatility of its stock using historical data for the past five years to through the end of the most recent period to estimate expected volatility.
[3]	The risk-free interest rate assumption is based on U.S. Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the stock option award.
[4]	The expected terms of employee stock options represents the weighted-average period the stock options are expected to remain outstanding and has been determined based on historical exercise behavior.

Note_9_Stockbased_Compensation4

Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Summary of Option Award Activity under Equity Compensation Plan (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Option Award Activity under Equity Compensation Plan [Abstract]
Outstanding at beginning of year (in Shares)	3,374,846	3,424,806	3,823,585
Outstanding at beginning of year	$16.26	$15.99	$15.80
Outstanding at end of year (in Shares)	2,142,971	3,374,846	3,424,806
Outstanding at end of year	$17.80	$16.26	$15.99
Vested and exercisable at end of year (in Shares)	1,383,888	2,828,365	3,174,843
Vested and exercisable at end of year	$16.86	$16.27	$15.86
Weighted average fair value of options granted during the period	$3.96	$2.25
Granted (in Shares)	399,550	429,800
Granted	$22.74	$15.62	$0
Exercised (in Shares)	-1,551,400	-345,302	-281,993
Exercised	$15.73	$12.60	$12.85
Forfeited and Expired (in Shares)	-80,025	-134,458	-116,786
Forfeited and Expired	$17.90	$16.78	$17.13

Note_9_Stockbased_Compensation5

Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Summary of Stock Option Information (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Exercise Price
Shares Outstanding (in Shares)	2,142,971
Weighted Ag. Contractual Years Remaining	2 years 346 days
Weighted Avg. Exercise Price Per Share	$17.80
Number Vested and Exercisable (in Shares)	1,383,888
Weighted Avg. Exercise Price Per Share for Vested and Exercisable	$16.86
Range 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Exercise Price	$12.63
Upper Exercise Price	$14.73
Shares Outstanding (in Shares)	54,995
Weighted Ag. Contractual Years Remaining	211 days
Weighted Avg. Exercise Price Per Share	$14.40
Number Vested and Exercisable (in Shares)	52,395
Weighted Avg. Exercise Price Per Share for Vested and Exercisable	$14.45
Range 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Exercise Price	$14.74
Upper Exercise Price	$16.83
Shares Outstanding (in Shares)	834,187
Weighted Ag. Contractual Years Remaining	2 years 226 days
Weighted Avg. Exercise Price Per Share	$15.41
Number Vested and Exercisable (in Shares)	540,854
Weighted Avg. Exercise Price Per Share for Vested and Exercisable	$15.32
Range 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Exercise Price	$16.84
Upper Exercise Price	$18.94
Shares Outstanding (in Shares)	854,289
Weighted Ag. Contractual Years Remaining	2 years 328 days
Weighted Avg. Exercise Price Per Share	$18.10
Number Vested and Exercisable (in Shares)	770,889
Weighted Avg. Exercise Price Per Share for Vested and Exercisable	$18.01
Range 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Exercise Price	$18.95
Upper Exercise Price	$33.27
Shares Outstanding (in Shares)	399,500
Weighted Ag. Contractual Years Remaining	4 years 36 days
Weighted Avg. Exercise Price Per Share	$22.60
Number Vested and Exercisable (in Shares)	19,750
Weighted Avg. Exercise Price Per Share for Vested and Exercisable	$20.21

Note_9_Stockbased_Compensation6

Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Summary of Restricted Stock Unit Award Activity under Equity Compensation Plan (Restricted Stock Units (RSUs) [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units (RSUs) [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Summary of Restricted Stock Unit Award Activity under Equity Compensation Plan [Line Items]
Unvested at January1,	1,213,698	1,210,532	1,325,817
Unvested at January1,	$16.04	$16.04	$16.01
Granted	17,017	183,111	41,000
Granted	$27.63	$15.95	$16.76
Vested	-128,659	-130,265	-114,605
Vested	$16.07	$16.01	$16
Forfeited and Expired	-28,510	-49,680	-41,680
Forfeited and Expired	$16.23	$15.75	$15.97
Outstanding (unvested) at end of year	1,073,546	1,213,698	1,210,532
Outstanding (unvested) at end of year	$16.22	$16.04	$16.04

Note_9_Stockbased_Compensation7

Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Fair Value Assumptions - Performance Shares (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Fair Value Assumptions - Performance Shares [Line Items]
Weighted average fair value of PRSUs granted (in Dollars per share)	$3.96		$2.25
Performance Shares [Member]
Note 9 - Stock-based Compensation and Employee Benefit Plans (Details) - Fair Value Assumptions - Performance Shares [Line Items]
Dividend yield (1)	1.06%	[1]
Expected volatility (2)	26.11%	[2]
Average peer volatility(2)	36.01%	[2]
Average peer correlation coefficient(3)	0.58%	[3]
Risk-free interest rate (4)	0.66%	[4]
Expected term (5)	2 years 292 days	[5]
Weighted average fair value of PRSUs granted (in Dollars per share)	$23.85
[1]	The dividend yield, used to project stock price to the end of the performance period, is based on our historical experience and future expectation of dividend payouts. Total shareholder 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]	We (or peer company) estimated volatility using our (or their) 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 U.S. Treasury securities at a constant maturity with a maturity period that most closely resembles the expected term of the performance award.
[5]	Since Monte Carlo valuation is an open form model that uses an expected life commensurate with the performance period, the expected life of the PRSUs was assumed to be the period from the grant date to the end of the performance period.

Note_10_Company_Share_Repurcha1

Note 10 - Company Share Repurchase Program (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	19-May-11	Dec. 31, 2010	Nov. 13, 2008
Disclosure Text Block Supplement [Abstract]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				10,000,000	2,020,956	3,000,000
Treasury Stock, Shares, Acquired	0	0	0
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	7,438,556

Note_11_Segment_Information_De

Note 11 - Segment Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Note 11 - Segment Information (Details) [Line Items]
Number of Operating Segments	2
Depreciation, Depletion and Amortization	$92,893	$86,129	$85,056
Trucking (Asset-Based) Segment [Member]
Note 11 - Segment Information (Details) [Line Items]
Number of Operating Segments	3
Depreciation, Depletion and Amortization	88,200	81,000	79,700
Non-Asset-Based Segment [Member]
Note 11 - Segment Information (Details) [Line Items]
Number of Operating Segments	2
Depreciation, Depletion and Amortization	$4,700	$5,100	$5,300

Note_11_Segment_Information_De1

Note 11 - Segment Information (Details) - Revenue and Operating Income Between Assets-Based and Non-Asset-Based Segments (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									$1,102,332		$969,237		$936,036
Percentage of revenues									100.00%		100.00%		100.00%
Operating income	52,782	39,791	38,899	31,250	32,165	24,274	31,925	25,544	162,722		113,909		108,267
Percentage of operating income									100.00%		100.00%		100.00%
Operating Segments [Member] | Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									892,124	[1]	822,188	[1]	836,357	[1]
Percentage of revenues									80.90%		84.80%		89.30%
Operating income									147,424		106,167		103,013
Percentage of operating income									90.60%		93.20%		95.10%
Operating Segments [Member] | Non-Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									214,378		151,194		105,794
Percentage of revenues									19.40%		15.60%		11.30%
Operating income									15,298		7,742		5,254
Percentage of operating income									9.40%		6.80%		4.90%
Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,106,502		973,382		942,151
Intersegment Eliminations [Member] | Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									-65		-120		-112
Percentage of revenues									0.00%		0.00%		0.00%
Intersegment Eliminations [Member] | Non-Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									($4,105)		($4,025)		($6,003)
Percentage of revenues									-0.30%		-0.40%		-0.60%
[1]	These items represent non-GAAP financial measures and are not substitutes for, and should be considered in addition to, the GAAP financial measures presented in the previous table.

Note_11_Segment_Information_De2

Note 11 - Segment Information (Details) - Reconciliation of Revenue from Segments to Consolidated, Asset-Based (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									$1,102,332		$969,237		$936,036
Revenue, net of fuel surcharge and intersegment transactions	273,653	227,829	218,908	205,596	206,300	195,847	200,104	189,600	925,985		791,851		752,151
Less: Trucking fuel surcharge revenue									-176,347		-177,386		-183,885
Operating expenses									939,610		855,328		827,769
Operating income	52,782	39,791	38,899	31,250	32,165	24,274	31,925	25,544	162,722		113,909		108,267
Intersubsegment Eliminations [Member] | Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									-65	[1]	-120	[1]	-112	[1]
Less: Trucking fuel surcharge revenue									-176,347	[1]	-177,386	[1]	-183,885	[1]
Reportable Subsegments [Member] | Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating income									147,424	[1]	106,167	[1]	103,013	[1]
Operating Segments [Member] | Asset-Based Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									892,124	[1]	822,188	[1]	836,357	[1]
Operating expenses, net of fuel surcharge and intersegment transactions									568,288	[1]	538,515	[1]	549,347	[1]
Operating expenses, net of fuel surcharge and intersegment transactions									79.40%	[1]	83.50%	[1]	84.20%	[1]
Revenue, net of fuel surcharge and intersegment transactions									715,712	[1]	644,682	[1]	652,360	[1]
Less: Trucking fuel surcharge revenue									-176,347	[1]	-177,386	[1]	-183,885	[1]
Operating expenses									744,700	[1]	716,021	[1]	733,344	[1]
Operating expenses, percentage									83.50%		87.10%		87.70%
Operating income									147,424		106,167		103,013
Operating Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									$1,106,502		$973,382		$942,151
[1]	These items represent non-GAAP financial measures and are not substitutes for, and should be considered in addition to, the GAAP financial measures presented in the previous table.

Note_11_Segment_Information_De3

Note 11 - Segment Information (Details) - Reconciliation of Revenue from Segments to Consolidated, Non-Asset-Based (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue	$273,653	$227,829	$218,908	$205,596	$206,300	$195,847	$200,104	$189,600	$925,985	$791,851	$752,151
Operating expenses									939,610	855,328	827,769
Operating income	52,782	39,791	38,899	31,250	32,165	24,274	31,925	25,544	162,722	113,909	108,267
Intersubsegment Eliminations [Member] | Non-Asset-Based Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue									-4,105	-4,025	-6,003
Reportable Subsegments [Member] | Non-Asset-Based Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue									210,273	147,169	99,791
Operating expenses									194,975	139,427	94,537
Operating expenses, percentage									92.70%	94.70%	94.70%
Operating income									15,298	7,742	5,254
Operating Segments [Member] | Non-Asset-Based Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue									214,378	151,194	105,794
Operating expenses									199,080	143,452	100,540
Operating expenses, percentage									92.90%	94.90%	95.00%
Operating income									$15,298	$7,742	$5,254

Note_11_Segment_Information_De4

Note 11 - Segment Information (Details) - Gross Margin Percentage of Segments (Brokerage and Intermodal [Member])	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Brokerage and Intermodal [Member]
Segment Reporting Information [Line Items]
Combined Brokerage and Intermodal gross margin percent (1)	15.00%	[1]	12.50%	[1]	13.20%	[1]
[1]	Gross margin percentage is based on revenue net of intersegment elimination.

Note_12_Acquisition_of_BarrNun2

Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) (Barr-Nunn Transportation, Inc [Member], USD $)	0 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 02, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014
Barr-Nunn Transportation, Inc [Member]
Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Acquisition, Value of Business	$112,400,000
Business Combination, Consideration Transferred	111,200,000	110,500,000	110,517,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred				700,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		3,500,000	3,500,000	3,500,000
Escrow Deposit	8,000,000
Percentage of Acquired Business, Assets		12.00%	12.00%	12.00%
Percentage of Acquired Business, Revenue				3.00%
Percentage of Acquired Business, Net Income				3.80%
Business Combination, Acquisition Related Costs				$429,000

Note_12_Acquisition_of_BarrNun3

Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Pro Forma Consolidated Results of Operations, Unaudited (Barr-Nunn Transportation, Inc [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Barr-Nunn Transportation, Inc [Member]
Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Pro Forma Consolidated Results of Operations, Unaudited [Line Items]
Total revenue	$1,192,745	$1,087,790	$1,052,711
Net income	$109,787	$78,274	$72,376

Note_12_Acquisition_of_BarrNun4

Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Allocation of the Purchase Price (USD $)	12 Months Ended	0 Months Ended	1 Months Ended	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Oct. 02, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Allocation of the Purchase Price [Line Items]
Cash paid pursuant to Stock Purchase and Real Estate Agreements	$110,517
Adjustments to recognize assets and liabilities at acquisition-date fair value:
Claims accruals	-30,037		-30,037	-30,037	-24,505	-26,232
Goodwill	47,067		47,067	47,067	10,257	10,276
Barr-Nunn Transportation, Inc [Member]
Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Allocation of the Purchase Price [Line Items]
Total consideration transferred		111,200	110,500	110,517
Cash paid pursuant to Stock Purchase and Real Estate Agreements				110,517
Historical book value of Barr-Nunn’s assets and liabilities (excluding cash)	71,656		71,656	71,656
Adjustments to recognize assets and liabilities at acquisition-date fair value:
Property, and equipment				3,349
Liabilities				-5,023
Fair value of tangible net assets acquired	69,982		69,982	69,982
Intangible assets	3,700		3,700	3,700
Total assets	122,675		122,675	122,675
Accounts payable	-3,311		-3,311	-3,311
Accrued liabilities	-5,638		-5,638	-5,638
Claims accruals	-3,209		-3,209	-3,209
Excess of consideration transferred over the net amount of assets and liabilities recognized, including $3.5 million attributable to the fair value of a potential earn-out obligation (goodwill)				36,835
Trade receivables	11,380		11,380	11,380
Other current assets	2,316		2,316	2,316
Property and equipment	68,444		68,444	68,444
Goodwill	$36,835		$36,835	$36,835

Note_12_Acquisition_of_BarrNun5

Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Allocation of the Purchase Price (Parentheticals) (Barr-Nunn Transportation, Inc [Member], USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Barr-Nunn Transportation, Inc [Member]
Note 12 - Acquisition of Barr-Nunn Transportation, Inc. (Details) - Allocation of the Purchase Price (Parentheticals) [Line Items]
Fair value of a potential earn-out obligation (goodwill)	$3.50

Note_13_Quarterly_Financial_Da2

Note 13 - Quarterly Financial Data (unaudited) (Details) (Barr-Nunn Transportation, Inc [Member])	Oct. 02, 2014
Barr-Nunn Transportation, Inc [Member]
Note 13 - Quarterly Financial Data (unaudited) (Details) [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%

Note_13_Quarterly_Financial_Da3

Note 13 - Quarterly Financial Data (unaudited) (Details) - Quarterly Financial Information (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information [Abstract]
Revenue, before fuel surcharge	$273,653	$227,829	$218,908	$205,596	$206,300	$195,847	$200,104	$189,600	$925,985	$791,851	$752,151
Income from operations	52,782	39,791	38,899	31,250	32,165	24,274	31,925	25,544	162,722	113,909	108,267
Net income attributable to Knight	$32,938	$25,100	$25,761	$19,064	$20,101	$15,059	$18,939	$15,183	$102,862	$69,282	$64,117
Earnings per common share:
Basic (in Dollars per share)	$0.40	$0.31	$0.32	$0.24	$0.25	$0.19	$0.24	$0.19	$1.27	$0.87	$0.80
Diluted (in Dollars per share)	$0.40	$0.31	$0.31	$0.23	$0.25	$0.19	$0.24	$0.19	$1.25	$0.86	$0.80

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - Valuation and Qualifying Accounts and Reserves (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Allowance for doubtful trade receivables:
Provision for Bad Debt	$1,351		$1,008		$883
Allowance for Trade Receivables [Member]
Allowance for doubtful trade receivables:
Balance at Beginning of Period	2,409		1,917		1,651
Provision for Bad Debt	1,309		952		931
Other Accounts	146	[1]		[1]		[1]
Bad Debt Write-offs	-509		-460		-665
Balance at End of Period	3,355		2,409		1,917
Allowance for Notes Receivable [Member]
Allowance for doubtful trade receivables:
Balance at Beginning of Period	312		291		416
Provision for Bad Debt	42		55		-48
Bad Debt Write-offs	-3		-34		-77
Balance at End of Period	$351		$312		$291
[1]	Addition to allowance for doubtful accounts following acquisition of Barr-Nunn.