| Pay vs Performance Disclosure | 12 Months Ended |
| Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) |
| Pay vs Performance Disclosure [Table] | | | |
| Pay vs Performance [Table Text Block] | Summary (1) Compensation (2) Average (3) Average (2)(3) Value of Initial Fixed $100 Investment (4) based on: Net Income Adjusted (6) Year Total Peer Group (5) 2022 $10,529,870 $9,724,702 $3,425,442 $3,231,790 $125 $101 $940,524 35.3 % 2021 10,233,276 13,016,105 3,328,925 4,066,077 144.14 126.45 844,245 34.3 % 2020 5,432,670 7,581,756 1,891,881 2,370,415 123.02 104.41 506,421 27.9 % | | |
| Company Selected Measure Name | adjusted operating margin | | |
| Named Executive Officers, Footnote [Text Block] | Amounts reported are the total compensation reported for Robert C. Biesterfeld Jr. in the Summary Compensation Table. Robert C. Biesterfeld Jr. served as our CEO for each of the years presented. | | |
| PEO Total Compensation Amount | $ 10,529,870 | $ 10,233,276 | $ 5,432,670 |
| PEO Actually Paid Compensation Amount | $ 9,724,702 | 13,016,105 | 7,581,756 |
| Adjustment To PEO Compensation, Footnote [Text Block] | Amounts reported represent the amount of “Compensation Actually Paid”, as computed in accordance with SEC rules. Our CEO does not participate in a pension plan; therefore, we did not report a change in pension value for any of the years reflected in this table, and a deduction from the Summary Compensation Table total related to pension value is not needed. Compensation Actually Paid to CEO reflects the following adjustments from Total Compensation reported in the Summary Compensation Table: 2022 2021 2020 Compensation Reported in Summary Compensation Table $10,529,870 $10,233,276 $5,432,670 Less: Value of awards reported in Summary Compensation Table (6,477,576) (5,924,530) (4,074,949) Plus: Year-end value of awards granted during the period that are unvested and outstanding 4,962,627 5,494,531 4,737,018 Plus: Year-end value of awards granted during the period that vested in the period 2,220,560 1,840,763 521,649 Plus: Increase (decrease) in fair value of equity awards that were granted during a prior period that vested (597,907) 780,905 158,698 Plus: Increase (decrease) in fair value of equity awards that were granted during a prior period that remain unvested and outstanding (912,872) 591,160 985,472 Less: Prior year fair value of awards that were granted during a prior period that failed to vest — — (178,802) Total Adjustments (805,168) 2,782,829 2,149,086 Compensation Actually Paid $9,724,702 $13,016,105 $7,581,756 | | |
| Non-PEO NEO Average Total Compensation Amount | $ 3,425,442 | 3,328,925 | 1,891,881 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 3,231,790 | 4,066,077 | 2,370,415 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Amounts reported are the total compensation reported for Michael P. Zechmeister, Arun D. Rajan, Mac S. Pinkerton, and Michael J. Short for 2022 and 2021. Amounts reported are the total compensation reported for Michael P. Zechmeister, Christopher J. O’Brien, Mac S. Pinkerton, and Michael J. Short for 2020. Average Compensation Actually Paid to Non-CEO NEOs reflects the following adjustments from Average Total Compensation reported in the Summary Compensation Table: 2022 2021 2020 Compensation Reported in Summary Compensation Table $3,425,442 $3,328,925 $1,891,881 Less: Value of awards reported in Summary Compensation Table (1,678,375) (2,003,480) (1,039,562) Plus: Year-end value of awards granted during the period that are unvested and outstanding 1,287,775 1,717,221 1,211,225 Plus: Year-end value of awards granted during the period that vested in the period 569,859 731,361 130,315 Plus: Increase (decrease) in fair value of equity awards that were granted during a prior period that vested (150,241) 183,273 54,967 Plus: Increase (decrease) in fair value of equity awards that were granted during a prior period that remain unvested and outstanding (222,670) 108,777 225,452 Less: Prior year fair value of awards that were granted during a prior period that failed to vest — — (103,863) Total Adjustments (193,652) 737,152 478,534 Compensation Actually Paid $3,231,790 $4,066,077 $2,370,415 | | |
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | | | |
| Compensation Actually Paid vs. Net Income [Text Block] | Company Actually Paid versus Total Net Income | | |
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | Company Actually Paid versus Adjusted Operating Margin % | | |
| Total Shareholder Return Vs Peer Group [Text Block] | Total shareholder return as calculated based on a fixed investment of one hundred dollars measured from the market close on December 31, 2019 (the last trading day of 2019) through and including the end of the fiscal year for each year reported in the table.Our peer group used for the TSR calculation is the NASDAQ Transportation Index, which is the industry index used to show our performance in our Form 10-K. | | |
| Tabular List [Table Text Block] | The following table lists the most important financial performance measures we used to link Compensation Actually Paid to the NEOs for fiscal 2022 to our performance: Financial Performance Measures Adjusted Pre-tax Income (APTI) (1) Diluted Earnings Per Share Adjusted Gross Profit (2) Adjusted Operating Margin (2) (1) Adjusted pre-tax income is a non-GAAP financial measure. Refer to page 54 (2) Additional information about adjusted gross profit and adjusted operating margin, including a reconciliation to gross profit and operating margin, is available in our annual report on Form 10-K for the year ended December 31, 2022. | | |
| Total Shareholder Return Amount | $ 125 | 144.14 | 123.02 |
| Peer Group Total Shareholder Return Amount | 101 | 126.45 | 104.41 |
| Net Income (Loss) | $ 940,524 | $ 844,245 | $ 506,421 |
| Company Selected Measure Amount | 0.353 | 0.343 | 0.279 |
| PEO Name | Robert C. Biesterfeld Jr. | Robert C. Biesterfeld Jr. | Robert C. Biesterfeld Jr. |
| Additional 402(v) Disclosure [Text Block] | Adjusted pre-tax income is a non-GAAP financial measure. Refer to page 54 (2) Additional information about adjusted gross profit and adjusted operating margin, including a reconciliation to gross profit and operating margin, is available in our annual report on Form 10-K for the year ended December 31, 2022. | | |
| Measure [Axis]: 1 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Non-GAAP Measure Description [Text Block] | Our company-selected measure, which is the measure we believe represents the most important financial performance not otherwise presented in the table above that we use to link Compensation Actually Paid to our NEOs for fiscal 2022 to our company’s performance, is adjusted operating margin. | | |
| PEO [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (805,168) | $ 2,782,829 | $ 2,149,086 |
| PEO [Member] | Value Of Awards, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (6,477,576) | (5,924,530) | (4,074,949) |
| PEO [Member] | Stock Awards Unvested, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 4,962,627 | 5,494,531 | 4,737,018 |
| PEO [Member] | Stock Awards Vested, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 2,220,560 | 1,840,763 | 521,649 |
| PEO [Member] | Equity Awards Reported Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (597,907) | 780,905 | 158,698 |
| PEO [Member] | Equity Awards Granted in Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (912,872) | 591,160 | 985,472 |
| PEO [Member] | Equity Awards Granted in Prior Years, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 0 | 0 | (178,802) |
| Non-PEO NEO [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (193,652) | 737,152 | 478,534 |
| Non-PEO NEO [Member] | Measure [Axis]: 1 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Adjusted Pre-tax Income (APTI)(1) | | |
| Non-PEO NEO [Member] | Measure [Axis]: 2 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Diluted Earnings Per Share | | |
| Non-PEO NEO [Member] | Measure [Axis]: 3 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Adjusted Gross Profit(2) | | |
| Non-PEO NEO [Member] | Measure [Axis]: 4 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Adjusted Operating Margin(2) | | |
| Non-PEO NEO [Member] | Value Of Awards, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (1,678,375) | (2,003,480) | (1,039,562) |
| Non-PEO NEO [Member] | Stock Awards Unvested, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 1,287,775 | 1,717,221 | 1,211,225 |
| Non-PEO NEO [Member] | Stock Awards Vested, Adjustment [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 569,859 | 731,361 | 130,315 |
| Non-PEO NEO [Member] | Equity Awards Reported Value [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (150,241) | 183,273 | 54,967 |
| Non-PEO NEO [Member] | Equity Awards Granted in Prior Years, Vested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (222,670) | 108,777 | 225,452 |
| Non-PEO NEO [Member] | Equity Awards Granted in Prior Years, Unvested [Member] | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ 0 | $ 0 | $ (103,863) |
