Long-Term Debt - Components of Notes Payable (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Notes payable	$ 392	$ 414
Deferred loan costs	(1)	(1)
Less: current portion	(22)	(22)
Long-term debt, noncurrent	$ 369	$ 391
Annual Contractual Interest Rate	3.42%	4.15%
Effective Interest Rate	3.52%	4.25%
Notes Payable | 2018 Term Loan A
Line of Credit Facility [Line Items]
Notes payable	$ 392	$ 414