Note 10. Employee Retirement Plans Employee Retirement Plans (Tables)

12 Months Ended

Dec. 31, 2022

Retirement Benefits [Abstract]

Defined Benefit Plan, Assumptions [Table Text Block]

Actuarial assumptions

	Year Ended December 31,
	2022	2021	2020
Assumptions used to determine benefit obligations at the annual measurement date were:
Obligation discount rate (1)	N/A	N/A	N/A
Assumptions used to determine net periodic benefit costs were:
Obligation discount rate (1)	N/A	N/A	2.71	%
Long-term rate of return on plan assets (1)	N/A	N/A	3.90	%

(1) Not applicable as of December 31, 2022 and 2021 and for the years ended December 31, 2022 and 2021 as all qualified pension plans were settled as of December 31, 2020.

Schedule of Costs of Retirement Plans [Table Text Block]

Components of Net Periodic Benefit Cost and Other Retirement Expenses

	Year Ended December 31,
	2022		2021		2020
	(in millions)
Expense Components
Service cost	$	—	$	—	$	—
Interest	0.4		0.4		14.8
Expected return on plan assets	—		—		(20.9)
Amortization of actuarial loss	0.3		0.3		6.0
Amortization of prior service cost	—		—		1.2
Settlement loss	—		—		151.5
Net periodic benefit cost	0.7		0.7		152.6
Defined contribution expense	9.1		8.6		7.5
Net expense	$	9.8	$	9.3	$	160.1

Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block]

Obligations and funded statusAt December 31, 2022 and 2021, the projected benefit obligations and net funded status of our Supplemental Executive Retirement Plan ("SERP") were $11.2 million and $14.5 million, respectively, which are included in accrued liabilities in our Consolidated Balance Sheets.

Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

Amounts recognized in other comprehensive income (loss)

	Year Ended December 31,
	2022		2021		2020
	(in millions)
Settlement of pension plan	$	—	$	—	$	151.5
Actuarial gain (loss)	2.6		0.4		10.4
Amortization of actuarial loss	0.3		0.3		6.0
Amortization of prior service cost	—		—		1.2
Total before income taxes	2.9		0.7		169.1
Income tax (benefit) expense	0.6		0.2		39.2
Net amount recognized in other comprehensive income (loss)	$	2.3	$	0.5	$	129.9