Debt and Credit Facility (Tables)

6 Months Ended

Jun. 30, 2023

Debt Disclosure [Abstract]

Summary of Senior Notes

The following table summarizes key details of our Senior Notes:

				Outstanding (in millions of dollars)
	Issuance Date	Maturity	Effective Interest Rate	As of June 30, 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					(11.1	)		(11.9	)
Total carrying amount				$	1,038.9		$	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 June 30, 2023		As of December 31, 2022
4.50% Senior Notes	$	439.8	$	438.7
4.625% Senior Notes	$	437.3	$	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 June 30, 2023 (in millions of dollars):

Revolving Credit Facility borrowing commitment	$	575.0
Borrowing base availability	$	575.0
Less: Outstanding borrowings under Revolving Credit Facility		(15.0	)
Less: Outstanding letters of credit under Revolving Credit Facility		(22.3	)
Remaining borrowing availability	$	537.7

Summary of Interest Expense Relating to Senior Notes and Revolving Credit Facility

nterest expense relating to our Senior Notes and Revolving Credit Facility (in millions of dollars):

	Quarter Ended June 30,						Six Months Ended June 30,
	2023			2022			2023			2022
Senior Notes, including debt issuance cost amortization	$	12.4		$	12.4		$	24.8		$	24.8
Revolving Credit Facility, including commitment fees and finance cost amortization		1.2			0.6			2.1			1.0
Interest expense capitalized as construction in progress		(1.5	)		(0.8	)		(2.9	)		(1.4	)
Total interest expense	$	12.1		$	12.2		$	24.0		$	24.4