Note 13. Common Stock and Stock-based Compensation Stockholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Nov. 16, 2018
Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount			$ 500.0	$ 350.0
Accelerated Share Repurchase Program, Authorized Amount					$ 350.0
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				13.7
Share-based Payment Arrangement, Accelerated Cost	$ 70.0
Treasury Stock, Value, Acquired, Cost Method	224.7	$ 500.1	$ 85.4
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 125.3
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	2.6
Treasury Stock [Member]
Share Repurchases [Line Items]
Treasury Stock, Shares, Acquired	13.7	17.2	2.8
Treasury Stock, Value, Acquired, Cost Method	$ 294.7	$ 430.1	$ 85.4
Additional Paid-in Capital [Member]
Share Repurchases [Line Items]
Treasury Stock, Shares, Acquired	2.6
Treasury Stock, Value, Acquired, Cost Method	$ (70.0)	$ (75.9)	$ 0.0