Stock Based Compensation - Additional Disclosures for Equity Based Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Additional Disclosures for equity-based plans
Shares withheld to settle payroll tax liabilities related to vesting of shares held by employees (in shares)	451,639	458,232	335,101
Time-based RSUs and RSAs
Additional Disclosures for equity-based plans
Total grant date fair value of shares granted (in millions)	$ 38	$ 38	$ 37
Total grant date fair value of shares vested (in millions)	$ 30	$ 28	$ 21
Shares withheld to settle payroll tax liabilities related to vesting of shares held by employees (in shares)	315,762	348,010	332,857
Performance-based RSUs and RSAs
Additional Disclosures for equity-based plans
Total grant date fair value of shares granted (in millions)	$ 4	$ 14	$ 10
Total grant date fair value of shares vested (in millions)	$ 11	$ 7	$ 0
Shares withheld to settle payroll tax liabilities related to vesting of shares held by employees (in shares)	135,877	110,222	2,244