	December 31, 2018		December 31, 2017
Credit Agreement with Banks, described below	$	20,000	$	43,000
Capital Leases, described below		102,859		89,916
Total debt		122,859		132,916
Less: current portion of long-term debt		18,082		14,083
Long-term debt, less current portion	$	104,777	$	118,833

The Company's liquidity needs arise primarily from capital investment in new equipment, land and structures, information technology and letters of credit required under insurance programs, as well as funding working capital requirements.

The Company is party to a revolving credit agreement (the Existing Credit Agreement) with a group of banks to fund capital investments, letters of credit and working capital needs. The Company has pledged certain land and structures, accounts receivable and other assets to secure indebtedness under this agreement.

The Existing Credit Agreement is a revolving credit facility for up to $250 million expiring in March 2020. The Existing Credit Agreement also has an accordion feature that allows for an additional $75 million in availability, subject to bank approval. The Existing Credit Agreement provides for a LIBOR rate margin range from 112.5 basis points to 225 basis points, base rate margins from minus 12.5 basis points to plus 50 basis points, an unused portion fee from 20 basis points to 30 basis points and letter of credit fees from 112.5 basis points to 225 basis points, in each case based on the Company's leverage ratio.

Under the Existing Credit Agreement, the Company must maintain certain financial covenants including a minimum fixed charge coverage ratio and a maximum leverage ratio. The Existing Credit Agreement provides for a pledge by the Company of certain land and structures, accounts receivable and other assets to secure indebtedness under this agreement.

At December 31, 2018, the Company had borrowings of $20.0 million and outstanding letters of credit of $27.7 million under the Existing Credit Agreement. At December 31, 2017, the Company had $43.0 million of outstanding borrowings and outstanding letters of credit of $33.9 million under the Existing Credit Agreement. The available portion of the Existing Credit Agreement may be used for general corporate purposes, including capital expenditures, working capital and letter of credit requirements as needed.

On February 5, 2019, the Company entered into the Sixth Amended and Restated Credit Agreement with its banking group (as amended, the Amended Credit Agreement). The amendment increased the amount of the revolver from $250 million to $300 million and extended the term until February 2024. The Amended Credit Agreement also has an accordion feature that allows for an additional $100 million availability, subject to bank approval. The amendment reduced the interest rate pricing grid. The Amended Credit Agreement provides for a LIBOR rate margin range from 100 basis points to 200 basis points, base rate margins from minus 50 basis points to plus 50 basis points, an unused portion fee from 17.5 basis points to 30 basis points and letter of credit fees from 100 basis points to 200 basis points in each case based on the Company’s leverage ratio. Under the Amended Credit Agreement, the Company must maintain a minimum debt service coverage ratio set at 1.25 to 1.00 and a maximum leverage ratio set at 3.25 to 1.00. The Amended Credit Agreement provides for a pledge by the Company of certain land and structures, accounts receivable and other assets to secure indebtedness under this agreement. The Amended Credit Agreement contains certain customary representations and warranties, affirmative and negative covenants and provisions relating to events of default. Under the Amended Credit Agreement, if an event of default occurs, the banks will be entitled to take various actions, including the acceleration of amounts due.

The Company is obligated under capital leases with seven year terms which include obligations covering revenue equipment totaling $102.9 million and $89.9 million as of December 31, 2018 and 2017, respectively. Amortization of assets held under the capital leases is included in depreciation and amortization expense. The weighted average interest rate for the capital leases at December 31, 2018 and 2017 is 3.41% and 3.07%, respectively.

The Company paid cash for interest of $5.2 million, $4.8 million, and $4.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.

The estimated fair value of total debt at December 31, 2018 and 2017 is $122.0 million and $132.3 million, respectively. The carrying amount of debt related to the revolving credit facility approximated fair value as of December 31, 2018 and 2017 due to the existence of variable interest rates, which approximate market rates. The fair value of the capital leases is based on current market interest rates for similar types of financial instruments which reflect Level 2 inputs.

The principal maturities of long-term debt, including interest on capital leases, for the next five years (in thousands) are as follows:

	Amount
2019	$	21,311
2020		41,311
2021		21,837
2022		19,947
2023		14,522
Thereafter		14,356
Total		133,284
Less: Amounts Representing Interest on Capital Leases		10,425
Total	$	122,859