Long-Term Debt (Schedule Of Long-Term Debt) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2019	Mar. 31, 2019	Sep. 18, 2017	May 11, 2017
Long-term debt [Line Items]
Less current portion		$ (70)	$ (49)
Total long-term debt		1,668	1,727
Vehicle Finance Leases [Member]
Long-term debt [Line Items]
Vehicle finance leases	[1]	$ 95	90
Borrowing margin (as a percent)		2.45%
Variable rate basis		one-month LIBOR
Senior Secured Term Loan Facility Maturing In 2023 [Member]
Long-term debt [Line Items]
Long-term debt	[2]		637
Unamortized debt issuance costs			5
Unamortized original issue discount			1
Senior Secured Term Loan Facility Maturing In 2026 [Member]
Long-term debt [Line Items]
Long-term debt	[3]	$ 593
Unamortized debt issuance costs		6
Unamortized original issue discount		1
5.125% Notes Maturing In 2024 [Member]
Long-term debt [Line Items]
Long-term debt	[4]	$ 742	740
Interest rate (as a percent)		5.125%
Unamortized debt issuance costs		$ 8	10
7.45% Notes Maturing In 2027 [Member]
Long-term debt [Line Items]
Long-term debt	[5]	$ 167	172
Interest rate (as a percent)		7.45%		7.45%
Unamortized fair value adjustments related to purchase accounting		$ 28	33
7.45% Notes Maturing In 2027 [Member] | Loans Payable [Member]
Long-term debt [Line Items]
Interest rate (as a percent)					7.45%
7.25% Notes Maturing In 2038 [Member]
Long-term debt [Line Items]
Long-term debt	[5]	$ 40	42
Interest rate (as a percent)		7.25%
7.25% Notes Maturing In 2038 [Member] | Loans Payable [Member]
Long-term debt [Line Items]
Interest rate (as a percent)					7.25%	7.25%	7.25%
Other [Member]
Long-term debt [Line Items]
Long-term debt	[6]	$ 100	94
Repayment of long-term debt		$ 91	$ 82

[1] We have entered into the Fleet Agreement which, among other things, allows us to obtain fleet vehicles through a leasing program. All leases under the Fleet Agreement are finance leases for accounting purposes. The lease rental payments include an interest component calculated using a variable rate based on one-month LIBOR plus other contractual adjustments and a borrowing margin totaling 2.45%.

[2] As of December 31, 2018, presented net of $5 million in unamortized debt issuance costs and $1 million in unamortized original issue discount paid as described below under “––Term Loan Facility.”

[3] As of December 31, 2019, presented net of $6 million in unamortized debt issuance costs and $1 million in unamortized original issue discount paid as described below under “––Term Loan Facility.”

[4] As of December 31, 2019 and 2018, presented net of $8 million and $10 million, respectively, in unamortized debt issuance costs related to the 2024 Notes.

[5] As of December 31, 2019 and 2018, collectively presented net of $28 million and $33 million, respectively, of unamortized fair value adjustments related to purchase accounting, which increases the effective interest rate from the coupon rates shown above.

[6] As of December 31, 2019 and 2018, includes approximately $91 million and $82 million, respectively, of future payments in connection with acquisitions as further described in Note 7.