Note 8. Short And Long-Term Debt Unsecured Notes (Details) - Senior Notes - USD ($) $ in Millions	Feb. 15, 2019	Dec. 31, 2018
4.50% Senior Notes
Debt Instrument [Line Items]
Interest Rate		4.50%
5.25% Senior Notes
Debt Instrument [Line Items]
Interest Rate		5.25%
4.875% Senior Notes
Debt Instrument [Line Items]
Interest Rate		4.875%
Subsequent Event | 4.50% Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount	$ 450