Restructuring Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 6	$ 46	$ 234
IT Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring costs	12
Decrease to estimated expected costs remaining		20
Accrued liabilities under restructuring plan	1	6
Other restructuring costs	3
IT Restructuring | One-Time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring costs	7
Payments for restructuring	5
IT Restructuring | Consulting Fees
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring costs	5
Payments for restructuring	3
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Accrued liabilities under restructuring plan		$ 18
2017 Restructuring Plan | Contract Termination
Restructuring Cost and Reserve [Line Items]
Accrued liabilities under restructuring plan	12
Payments for restructuring	9
Restructuring costs	$ 3