Note 10. Employee Retirement Plans Employee Retirement Plans (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,378.9	$ 2,562.0	$ 4,858.0	$ 4,311.1
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	225.0
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	336.0
Terminal Funding Annuity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	15.0
Terminal Funding Annuity [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	155.0
Terminal Funding Annuity [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	185.0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Terminal Funding Annuity [Member]
Defined Benefit Plan Disclosure [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (131.2)