Stock Plans and Share-Based Compensation - Share-Based Compensation and Related Income Tax Benefit (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	$ 24	$ 13
Income Tax Benefit	9	28
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	10	2
Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	9	6
Restricted Stock Units and Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	2	2
Stock Awards for Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	2	2
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	$ 1	$ 1