Debt and Credit Facility (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Summary of Senior Notes

The following table summarizes key details of our outstanding Senior Notes:

				Outstanding (in millions of dollars)
	Issuance Date	Maturity	Effective Interest Rate	As of December 31, 2023			As of December 31, 2022
4.50% Senior Notes	May 2021	June 2031	4.7%	$	550.0		$	550.0
4.625% Senior Notes	November 2019	March 2028	4.8%		500.0			500.0
Total debt					1,050.0			1,050.0
Unamortized issuance costs					(10.2	)		(11.9	)
Total carrying amount				$	1,039.8		$	1,038.1

Summary of Fair Value of Outstanding Senior Notes

The following table presents the fair value of our outstanding Senior Notes, which are Level 1 liabilities (in millions of dollars):

	As of December 31,
	2023		2022
4.50% Senior Notes	$	474.1	$	438.7
4.625% Senior Notes	$	462.4	$	440.4

Schedule of Availability and Usage of Revolving Credit Facility

The following table summarizes availability and usage of our Revolving Credit Facility as determined by a borrowing base calculated as of December 31, 2023 (in millions of dollars):

Revolving Credit Facility borrowing commitment	$	575.0
Borrowing base availability	$	543.5
Less: Outstanding borrowings under Revolving Credit Facility		—
Less: Outstanding letters of credit under Revolving Credit Facility		(26.8	)
Remaining borrowing availability	$	516.7

Summary of Interest Relating to Senior Notes and Revolving Credit Facility

The following table presents interest expense relating to our Senior Notes and Revolving Credit Facility (in millions of dollars):

	Year Ended December 31,
	2023			2022			2021
Senior Notes interest expense, including debt issuance cost amortization	$	49.6		$	49.6		$	49.0
Revolving Credit Facility interest expense, including commitment fees and finance cost amortization		3.0			2.0			1.4
Interest expense on finance lease liabilities		0.7			0.3			0.3
Interest expense capitalized as construction in progress		(6.4	)		(3.6	)		(1.2	)
Total interest expense	$	46.9		$	48.3		$	49.5

Schedule of Future Principal Payments for Senior Notes and Revolving Credit Facility

The following table presents the future principal payments for our Senior Notes and Revolving Credit Facility as of December 31, 2023 (in millions of dollars):

Year ending December 31,
2024	$	—
2025		—
2026		—
2027		—
2028		500.0
Thereafter		550.0
Total	$	1,050.0