Debt - Debt Issuances (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Finance lease obligations	$ 20,000,000	$ 17,000,000
Principal debt balance	1,678,000,000	1,539,000,000
Debt issuance costs and unamortized discounts	(22,000,000)	(25,000,000)
Less: current maturities	(60,000,000)	(50,000,000)
Total Long-term Debt	1,596,000,000	1,464,000,000
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	82,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	150,000,000	0
Line of Credit Facility, Maximum Borrowing Capacity	750,000,000
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	750,000,000
Line of Credit Facility, Fair Value of Amount Outstanding	150,000,000	0
Line of Credit Facility, Remaining Borrowing Capacity	518,000,000
Term Loan A due 2022
Debt Instrument [Line Items]
Long-term debt, gross	652,000,000	664,000,000
Term Loan B due 2023
Debt Instrument [Line Items]
Long-term debt, gross	822,000,000	824,000,000
Senior Notes due 2024
Debt Instrument [Line Items]
Long-term debt, gross	$ 34,000,000	$ 34,000,000