The following tables summarize, by level within the fair value hierarchy, our derivative and other assets and liabilities that were accounted for at fair value on a recurring basis at March 31, 2024 and December 31, 2023:


	March 31, 2024
	Level 1		Level 2		Total
	(Thousands of dollars)
Assets:


United States treasury notes (b)	$	6,476	$	—	$	6,476
Corporate bonds (b)	—		10,266		10,266
Total assets	$	6,476	$	10,266	$	16,742

(a) The fair value is included in other current assets and other current liabilities in our consolidated balance sheets.

(b) The fair value is included in other current and noncurrent assets and other current and noncurrent liabilities in our consolidated balance sheets.


	December 31, 2023
	Level 1		Level 2		Total
	(Thousands of dollars)
Assets:
United States treasury notes (b)	$	6,496	$	—	$	6,496
Corporate bonds (b)	—		11,080		11,080
Total assets	$	6,496	$	11,080	$	17,576
Liabilities:
Derivative instruments - swaps (a)	$	—	$	13,920	$	13,920

(a) The fair value is included in other current assets and other current liabilities in our consolidated balance sheets.

(b) The fair value is included in other current and noncurrent assets and other current and noncurrent liabilities in our consolidated balance sheets.