Note 9 - Amendment of Marten Transport, Ltd. 2015 Equity Incentive Plan	6 Months Ended
Jun. 30, 2019
Notes to Financial Statements
Share-based Payment Arrangement [Text Block]	(10) Accounting for Share-based Payment Arrangement Compensation We account for share-based payment arrangements in accordance with FASB ASC 718, Compensation – Stock Compensation. During the first six months of 2019, there were no significant changes to the structure of our stock-based award plans. Pre-tax compensation expense related to stock options and performance unit awards recorded in the first six months of 2019 and 2018 was $1.0 million and $1.2 million, respectively.
2015 Equity Incentive Plan [Member]
Notes to Financial Statements
Share-based Payment Arrangement [Text Block]	(9) Amendment of Marten Transport, Ltd. 2015 Equity Incentive Plan At our 2019 Annual Meeting of Stockholders held on May 7, 2019, our stockholders approved an amendment to the Marten Transport, Ltd. 2015 Equity Incentive Plan, which was previously approved and adopted by our Board of Directors, subject to approval by our stockholders. The amendment increased the number of shares of common stock authorized for issuance under the Marten Transport, Ltd. 2015 Equity Incentive Plan by 1.3 million shares and the number of shares of common stock authorized for issuance pursuant to full-value awards by 558,334 shares. The amendment also adjusted certain numbers to reflect the stock split that occurred in July 2017.

Note 9 - Amendment of Marten Transport, Ltd. 2015 Equity Incentive Plan

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Text Block]

(10) Accounting for Share-based Payment Arrangement Compensation

We account for share-based payment arrangements in accordance with FASB ASC 718, Compensation – Stock Compensation. During the first six months of 2019, there were no significant changes to the structure of our stock-based award plans. Pre-tax compensation expense related to stock options and performance unit awards recorded in the first six months of 2019 and 2018 was $1.0 million and $1.2 million, respectively.

2015 Equity Incentive Plan [Member]

Notes to Financial Statements

Share-based Payment Arrangement [Text Block]

(9) Amendment of Marten Transport, Ltd. 2015 Equity Incentive Plan

At our 2019 Annual Meeting of Stockholders held on May 7, 2019, our stockholders approved an amendment to the Marten Transport, Ltd. 2015 Equity Incentive Plan, which was previously approved and adopted by our Board of Directors, subject to approval by our stockholders. The amendment increased the number of shares of common stock authorized for issuance under the Marten Transport, Ltd. 2015 Equity Incentive Plan by 1.3 million shares and the number of shares of common stock authorized for issuance pursuant to full-value awards by 558,334 shares. The amendment also adjusted certain numbers to reflect the stock split that occurred in July 2017.