Stock-Based Compensation - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) trading_day shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017
Stock-Based Compensation Details [Line Items]
Number of shares available for grant (shares)	11,000,000	13,000,000
Stock-based compensation expense, pre-tax | $	$ 42	$ 50	$ 57
Income tax benefit recognized in earnings | $	$ 11	$ 13	$ 14
Restricted Stock Units (RSUs)
Stock-Based Compensation Details [Line Items]
Performance period			3 years
Restricted Stock Units (RSUs) | Graded vesting after year one of service period
Stock-Based Compensation Details [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights (percent)	25.00%
Performance period	1 year
Restricted Stock Units (RSUs) | Graded vesting after year two of service period
Stock-Based Compensation Details [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights (percent)	25.00%
Performance period	2 years
Restricted Stock Units (RSUs) | Graded vesting after year three of service period
Stock-Based Compensation Details [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights (percent)	50.00%
Performance period	3 years
Performance Shares
Stock-Based Compensation Details [Line Items]
Performance period	3 years	3 years	3 years	3 years
Approximation of grant date fair value	50.00%
Performance Shares | Revenue
Stock-Based Compensation Details [Line Items]
Weighting of measurement components (percent)	25.00%
Performance Shares | Free Cash Flow
Stock-Based Compensation Details [Line Items]
Weighting of measurement components (percent)	25.00%
Performance Shares | Absolute Share Price
Stock-Based Compensation Details [Line Items]
Weighting of measurement components (percent)	50.00%
Performance Shares | Performance-Based
Stock-Based Compensation Details [Line Items]
Performance share grant basis - performance		0.6667
Performance share maximum overachievement	100.00%
Performance-based metric performance period (years)			1 year
Time-based metric performance period (years)		2 years
Performance Shares | Performance Based - Actual Results
Stock-Based Compensation Details [Line Items]
Performance-based metric performance period (years)	3 years
Performance Shares | TSR
Stock-Based Compensation Details [Line Items]
Performance period	3 years	3 years	3 years
Performance share grant basis - TSR		0.3333
Total number of trading days of performance period | trading_day	20
Performance Shares | Minimum
Stock-Based Compensation Details [Line Items]
Performance shares entitlement of original award grant (percent)	0.00%	0.00%
Performance Shares | Maximum
Stock-Based Compensation Details [Line Items]
Performance shares entitlement of original award grant (percent)	200.00%	200.00%
Equity Option | Graded vesting after year one of service period
Stock-Based Compensation Details [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights (percent)	25.00%
Equity Option | Graded vesting after year two of service period
Stock-Based Compensation Details [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights (percent)	25.00%
Equity Option | Graded vesting after year three of service period
Stock-Based Compensation Details [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights (percent)	50.00%
Options outstanding, term (years)	10 years