| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Document Information [Line Items] | |
| Document Type | PRE 14A |
| Amendment Flag | false |
| Entity Information [Line Items] | |
| Entity Registrant Name | Landstar System, Inc. |
| Entity Central Index Key | 0000853816 |
| Pay vs Performance Disclosure | 12 Months Ended | ||
| Dec. 31, 2022 USD ($) | Dec. 25, 2021 USD ($) | Dec. 26, 2020 USD ($) | |
| Pay vs Performance Disclosure [Table] | |||
| Pay vs Performance [Table Text Block] | PAY VERSUS PERFORMANCE As required by Section 953(a) of the Dodd-Frank Wall Street Reform and Consumer Protection Act, and Item 402(v) of Regulation S-K, pay-for-performance Compensation Discussion and Analysis The following table summarizes the “compensation actually paid” to (i) the Principal Executive Officer (“PEO”) and (ii) the average “compensation actually paid” to the remaining Named Executive Officers other than the PEO with respect to applicable fiscal years. “Compensation actually paid” does not correlate to the total amount of cash or equity compensation that the executive actually realized or was paid during the fiscal year. Instead, it is a nuanced calculation that includes the increase (or decrease) in value of certain elements of compensation ( i.e. i.e. Pay Versus Performance Table Year Summary Compensation Average Non-PEO Named Average Non-PEO Named Executives (4) Value of Initial Fixed Net Income Diluted Total Peer Group (a) (b) (c) (d) (e) (f) (g) (h) (i) 2022 4,574,748 2,935,420 1,796,669 1,281,181 153.21 122.45 430,914,000 11.76 2021 5,398,583 17,834,936 3,193,054 6,520,834 159.05 148.01 381,524,000 9.98 2020 2,699,091 4,945,811 1,231,859 1,175,865 122.56 114.50 192,106,000 4.98 (1) The dollar amounts reported in column (b) are the amounts of total compensation reported for Mr. Gattoni, the Company’s President and Chief Executive Officer and PEO, for each corresponding year in the “Total” column of the Summary Compensation Table included in the section “Compensation of Named Executives (2) The dollar amounts reported in column (c) represent the amount of “compensation actually paid” to Mr. Gattoni, as computed in accordance with Item 402(v) of Regulation S-K. S-K, Year Reported Summary Reported Value of Equity Equity Award Compensation 2022 4,574,748 1,429,976 (209,352 ) 2,935,420 2021 5,398,583 1,429,787 13,866,140 17,834.936 2020 2,699,091 1,429,976 3,676,696 4,945,811 (a) The grant date fair value of equity awards represents the total of the amounts reported in the “Stock Awards” column in the Summary Compensation Table for the applicable year. (b) The equity award adjustments for each applicable year include the addition (or subtraction, as applicable) of the following: (i) the year-end 10-K Year Year End Fair Year over Year Year over Year Fair Value at Value of Total 2022 872,415 (393,513 ) (688,254 ) — — (209,352 ) 2021 3,066,905 10,203,279 595,956 — — 13,866,140 2020 1,325,645 2,424,469 (73,418 ) — — 3,676,696 (3) The dollar amounts reported in column (d) represent the average of the amounts reported for the Company’s Named Executives as a group (excluding Mr. Gattoni) in the “Total” column of the Summary Compensation Table in each applicable year. The Named Executives (excluding Mr. Gattoni) included for purposes of calculating the average amounts in each applicable year are as follows: (i) for 2022, Messrs. Beacom, Coro, Kneller, Pensotti and Todd; (ii) for 2021, Messrs. Beacom, Coro, Kneller and Pensotti; and (iii) for 2020, Messrs. Beacom, Coro, Kneller and L. Kevin Stout. (4) The dollar amounts reported in column (e) represent the average amount of “compensation actually paid” to the Named Executives as a group (excluding Mr. Gattoni), as computed in accordance with Item 402(v) of Regulation S-K. S-K, Year Average Non-PEO Average Average Equity Average Non-PEO Named 2022 1,796,669 693,490 178,002 1,281,181 2021 3,193,054 723,584 4,051,364 6,520,834 2020 1,231,859 714,932 658,938 1,175,865 (a) The amounts deducted or added in calculating the total average equity award adjustments are as follows: Year Average Year over Year over Average Fair Average Total 2022 349,416 170,847 (183,146 ) (159,115 ) — 178,002 2021 1,342,266 2,684,379 24,719 — — 4,051,364 2020 662,675 8,754 (12,491 ) — — 658,938 (5) This column illustrates the Cumulative TSR that would have been realized as of the end of the measurement period, assuming reinvestment of dividends throughout, by an investor who invested $100 in the Company’s Common Stock at the beginning of the measurement period. (6) Represents the TSR that would have been realized by an investor, assuming reinvestment of dividends, who invested $100 in the peer group at the beginning of the measurement period. The peer group used for this purpose is the following published industry index: the Dow Jones Transportation Stock Index. The peer group referred to throughout this Pay For Performance section is separate and distinct from the peer group referred to in “Compensation Discussion and Analysis” (7) The dollar amounts reported represent the amount of net income reflected in the Co mpan (8) The Company determined diluted earnings per share to be the Company Selected Measure, which in the Company’s assessment represents the most important financial performance measure (that is not otherwise required to be disclosed in the table) used by the Company to link “compensation actually paid” to the Company’s Named Executive for the most recently completed fiscal year to Company performance. The dollar amounts reported represent the amount of diluted earnings per share reflected in the Company’s audited consolidated financial statements for the applicable year. | ||
| Company Selected Measure Name | diluted earnings per share | ||
| Named Executive Officers, Footnote [Text Block] | for 2022, Messrs. Beacom, Coro, Kneller, Pensotti and Todd; | for 2021, Messrs. Beacom, Coro, Kneller and Pensotti; | for 2020, Messrs. Beacom, Coro, Kneller and L. Kevin Stout. |
| Peer Group Issuers, Footnote [Text Block] | Represents the TSR that would have been realized by an investor, assuming reinvestment of dividends, who invested $100 in the peer group at the beginning of the measurement period. The peer group used for this purpose is the following published industry index: the Dow Jones Transportation Stock Index. The peer group referred to throughout this Pay For Performance section is separate and distinct from the peer group referred to in “Compensation Discussion and Analysis” | ||
| PEO Total Compensation Amount | $ 4,574,748 | $ 5,398,583 | $ 2,699,091 |
| PEO Actually Paid Compensation Amount | $ 2,935,420 | 17,834,936 | 4,945,811 |
| Adjustment To PEO Compensation, Footnote [Text Block] | The dollar amounts reported in column (c) represent the amount of “compensation actually paid” to Mr. Gattoni, as computed in accordance with Item 402(v) of Regulation S-K. S-K, Year Reported Summary Reported Value of Equity Equity Award Compensation 2022 4,574,748 1,429,976 (209,352 ) 2,935,420 2021 5,398,583 1,429,787 13,866,140 17,834.936 2020 2,699,091 1,429,976 3,676,696 4,945,811 (a) The grant date fair value of equity awards represents the total of the amounts reported in the “Stock Awards” column in the Summary Compensation Table for the applicable year. (b) The equity award adjustments for each applicable year include the addition (or subtraction, as applicable) of the following: (i) the year-end 10-K Year Year End Fair Year over Year Year over Year Fair Value at Value of Total 2022 872,415 (393,513 ) (688,254 ) — — (209,352 ) 2021 3,066,905 10,203,279 595,956 — — 13,866,140 2020 1,325,645 2,424,469 (73,418 ) — — 3,676,696 | ||
| Non-PEO NEO Average Total Compensation Amount | $ 1,796,669 | 3,193,054 | 1,231,859 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 1,281,181 | 6,520,834 | 1,175,865 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | The dollar amounts reported in column (e) represent the average amount of “compensation actually paid” to the Named Executives as a group (excluding Mr. Gattoni), as computed in accordance with Item 402(v) of Regulation S-K. S-K, Year Average Non-PEO Average Average Equity Average Non-PEO Named 2022 1,796,669 693,490 178,002 1,281,181 2021 3,193,054 723,584 4,051,364 6,520,834 2020 1,231,859 714,932 658,938 1,175,865 (a) The amounts deducted or added in calculating the total average equity award adjustments are as follows: Year Average Year over Year over Average Fair Average Total 2022 349,416 170,847 (183,146 ) (159,115 ) — 178,002 2021 1,342,266 2,684,379 24,719 — — 4,051,364 2020 662,675 8,754 (12,491 ) — — 658,938 | ||
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | “Compensation Actually Paid” and Cumulative TSR The following chart presents the amount of compensation actually paid to Mr. Gattoni (the PEO), the average amount of “compensation actually paid” to the Company’s Named Executives as a group (excluding Mr. Gattoni), and the Company’s cumulative TSR over the three years presented in the Pay Versus Performance table. | ||
| Compensation Actually Paid vs. Net Income [Text Block] | Compensation Actually Paid and Net Income The following chart presents the amount of compensation actually paid to Mr. Gattoni (the PEO), the average amount of compensation actually paid to the Company’s Named Executives as a group (excluding Mr. Gattoni), and the Company’s net income over the three years presented in the Pay Versus Performance table. | ||
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | Compensation Actually Paid and Diluted Earnings Per Share The following chart presents the amount of compensation actually paid to Mr. Gattoni (the PEO), the average amount of compensation actually paid to the Company’s Named Executives as a group (excluding Mr. Gattoni), and the Company’s diluted earnings per share over the three years presented in the Pay Versus Performance table. | ||
| Total Shareholder Return Vs Peer Group [Text Block] | Cumulative TSR of the Company and Cumulative TSR of the Dow Jones Transportation Stock Index As demonstrated by the following graph, the Company’s cumulative TSR over the three year period presented in the table was 53%, while the cumulative TSR of the peer group presented for this purpose, the Dow Jones Transportation Stock Index, was 22% over the three years presented in the table. | ||
| Tabular List [Table Text Block] | The most important financial performance measures used by the Company to link “compensation actually paid” to the Company’s Named Executives, for the most recently completed fiscal year, to the Company’s performance are as follows: • Operating income • Pre-tax • Diluted earnings per share • Total shareholder return | ||
| Total Shareholder Return Amount | $ 153.21 | 159.05 | 122.56 |
| Peer Group Total Shareholder Return Amount | 122.45 | 148.01 | 114.5 |
| Net Income (Loss) | $ 430,914,000 | $ 381,524,000 | $ 192,106,000 |
| Company Selected Measure Amount | 11.76 | 9.98 | 4.98 |
| PEO Name | Mr. Gattoni | ||
| Measure [Axis]: 1 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Operating income | ||
| Measure [Axis]: 2 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Pre-tax income per diluted share | ||
| Measure [Axis]: 3 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Diluted earnings per share | ||
| Measure [Axis]: 4 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Total shareholder return | ||
| PEO [Member] | Reported Value of Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ 1,429,976 | $ 1,429,787 | $ 1,429,976 |
| PEO [Member] | Equity Award Adjustments [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (209,352) | 13,866,140 | 3,676,696 |
| PEO [Member] | Year End Fair Value of Equity Awards Granted in the Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 872,415 | 3,066,905 | 1,325,645 |
| PEO [Member] | Year over Year Change in Fair Value of Outstanding and Unvested Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (393,513) | 10,203,279 | 2,424,469 |
| PEO [Member] | Year over Year Change in Fair Value of Equity Awards Granted in Prior Years that Vested in the Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (688,254) | 595,956 | (73,418) |
| Non-PEO NEO [Member] | Reported Value of Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 693,490 | 723,584 | 714,932 |
| Non-PEO NEO [Member] | Equity Award Adjustments [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 178,002 | 4,051,364 | 658,938 |
| Non-PEO NEO [Member] | Year End Fair Value of Equity Awards Granted in the Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 349,416 | 1,342,266 | 662,675 |
| Non-PEO NEO [Member] | Year over Year Change in Fair Value of Outstanding and Unvested Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 170,847 | 2,684,379 | 8,754 |
| Non-PEO NEO [Member] | Year over Year Change in Fair Value of Equity Awards Granted in Prior Years that Vested in the Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (183,146) | $ 24,719 | $ (12,491) |
| Non-PEO NEO [Member] | Average Fair Value at the End of the Prior Year of Equity Awards that Failed to Meet Vesting Conditions in the Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ (159,115) | ||
