Condensed Consolidated Balance Sheets - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents		$ 79,184	$ 76,649
Cash and cash equivalents — restricted		55,616	73,657
Restricted investments, held to maturity, amortized cost	[1]	22,281	22,232
Trade receivables, net of allowance for doubtful accounts of $14,723 and $14,829, respectively		589,983	574,265
Equipment sales receivables		1,197	8,925
Notes receivable, net		4,059	4,742
Prepaid expenses		62,212	58,525
Assets held for sale		30,444	25,153
Income tax receivable		26,841	55,114
Other current assets		23,684	23,945
Total current assets		895,501	923,207
Property and equipment:
Revenue equipment		2,217,814	2,197,158
Land and land improvements		219,726	216,676
Buildings and building improvements		356,508	357,409
Furniture and fixtures		50,659	43,131
Shop and service equipment		23,221	22,864
Leasehold improvements		9,991	9,905
Total property and equipment		2,877,919	2,847,143
Less: accumulated depreciation and amortization		(532,056)	(462,922)
Property and equipment, net		2,345,863	2,384,221
Notes receivable, long-term		11,496	11,060
Goodwill	[2]	2,910,101	2,887,867
Intangible assets, net		1,453,395	1,440,903
Other long-term assets, restricted cash, and investments		39,730	36,184
Total assets		7,656,086	7,683,442
Current liabilities:
Accounts payable		112,308	119,867
Accrued payroll and purchased transportation		117,002	107,017
Accrued liabilities		187,859	186,076
Claims accruals – current portion		154,190	147,285
Long-term debt – current portion		441	30
Capital lease obligations – current portion		46,279	48,972
Dividend payable – current portion		277	303
Total current liabilities		618,356	609,550
Revolving line of credit	[3],[4],[5]	55,000	125,000
Long-term debt – less current portion		364,411	364,771
Capital lease obligations – less current portion		120,747	127,132
Accounts receivable securitization		280,000	305,000
Claims accruals – less current portion		212,804	206,144
Deferred tax liabilities		671,111	679,077
Long-term dividend payable and other long-term liabilities		24,465	26,398
Total liabilities		2,346,894	2,443,072
Commitments and contingencies (Note 13)
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 10,000 shares authorized; none issued		0	0
Class A common stock, par value $0.01 per share; authorized 500,000 shares; 178,292 and 177,998 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively		1,783	1,780
Class B common stock, par value $0.01 per share; Authorized 250,000 shares; none issued		0	0
Additional paid-in capital		4,225,661	4,219,214
Retained earnings		1,079,543	1,016,738
Total Knight-Swift stockholders' equity		5,306,987	5,237,732
Noncontrolling interest		2,205	2,638
Total stockholders’ equity		5,309,192	5,240,370
Total liabilities and stockholders’ equity		7,656,086	7,683,442
Common Class A [Member]
Stockholders’ equity:
Total stockholders’ equity		$ 1,783	$ 1,780

[1] Restricted investments are included in "Restricted investments, held to maturity, amortized cost."

[2] Except for the net accumulated amortization related to deferred tax assets in the Knight Trucking segment, the net carrying amount and gross carrying amount are equal since there are no accumulated impairment losses.

[3] As of March 31, 2018 and December 31, 2017, interest accrued on the Revolver at 2.81% and 2.69%, respectively. The commitment fee for the unused portion of the Revolver is based on the Company's consolidated leverage ratio and ranges from 0.07% to 0.20%. As of March 31, 2018 and December 31, 2017, commitment fees on the unused portion of the Revolver accrued at 0.10% and 0.13%, respectively

[4] Refer to Note 16 for information regarding the fair value of long-term debt.

[5] The Company also had outstanding letters of credit under the Revolver of $115.2 million and $122.3 million at March 31, 2018 and December 31, 2017, respectively. As of March 31, 2018 and December 31, 2017, letter of credit fees accrued at 1.00% and 1.13%, respectively. These letters of credit are maintained for the benefit of regulatory authorities, insurance companies, and state departments of insurance for the purpose of satisfying certain collateral requirements, primarily related to the Company's automobile, workers' compensation, and general insurance liabilities.