Employee Stock-based Compensation Plans - Employee Purchases and Aggregate Cost (Details) - Employee Stock Puchase Program - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Equity, Class of Treasury Stock [Line Items]
Employee share purchases (in shares)	0.3	0.7	0.6
Aggregate cost	$ 10	$ 14	$ 20