Note 10. Employee Retirement Plans Accumulated Benefit Obligations and Funded Status (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 557,900,000	$ 453,200,000
Defined Benefit Plan, Benefit Obligation	557,900,000	453,200,000	$ 490,000,000.0
Defined Benefit Plan, Service Cost	100,000	100,000	200,000
Defined Benefit Plan, Interest Cost	19,700,000	18,300,000	19,600,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(22,200,000)	(20,200,000)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	105,600,000	(35,600,000)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	1,500,000	0
Defined Benefit Plan, Other Cost (Credit)	0	600,000	0
Defined Benefit Plan, Plan Assets, Amount	548,500,000	478,700,000	$ 488,000,000.0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	90,900,000	(20,700,000)
Defined Benefit Plan, Plan Assets, Contributions by Employer	1,100,000	31,600,000
Defined Benefit Plan, Plan Assets, Benefits Paid	(22,200,000)	(20,200,000)
Assets for Plan Benefits, Defined Benefit Plan	5,500,000	39,400,000
Liability, Defined Benefit Plan	(14,900,000)	(13,900,000)
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (9,400,000)	$ 25,500,000
Defined Benefit Plan, Funded Percentage	98.30%	105.60%
Defined Benefit Plan, Plan Assets, Expected to be Returned to Employer, Amount	$ 0