Note 13. Common Stock and Stock-based Compensation Stockholders Equity (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 23, 2020	Mar. 07, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock Repurchase Program, Authorized Amount												$ 250.0	$ 350.0
Stock Repurchase Program, Number of Shares Authorized to be Repurchased													13,700,000
Treasury Stock, Shares, Acquired								866,715
Treasury Stock, Value, Acquired, Cost Method								$ 19.0	$ 193.1	$ 224.7	$ 500.1
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 182.2	$ 0.0	$ 89.9	$ 89.9	$ 125.3	$ 186.1	$ 287.0	$ 331.0	$ 182.2	125.3
Total Shares Repurchased Under Program	2,974,922	17,421,690							2,974,922
Total Shares Repurchased Under Program, Value	$ 67.8	$ 350.0							$ 67.8
Share-based Payment Arrangement, Accelerated Cost										$ 70.0
Share-based Payment Arrangement, Cash Used to Settle Award	$ 1.8
Treasury Stock [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Treasury Stock, Shares, Acquired	2,974,922	4,466,896	0	1,850,000	2,933,474	5,171,489	2,133,116		9,300,000	13,700,000	17,200,000
Treasury Stock, Value, Acquired, Cost Method	$ 67.8	$ 89.9	$ 0.0	$ 35.4	$ 60.8	$ 100.9	$ 44.0		$ 193.1	$ 294.7	$ 430.1
Additional Paid-in Capital [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Treasury Stock, Shares, Acquired										2,600,000
Treasury Stock, Value, Acquired, Cost Method										$ 70.0	$ 75.9