Long-Term Debt (Schedule Of Long-Term Debt) (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2020	Dec. 31, 2019	Apr. 30, 2019	Mar. 31, 2019
Long-term debt [Line Items]
Less current portion	[1]	$ (100)	$ (69)
Total long-term debt		1,565	1,666
Fleet Agreement [Member]
Long-term debt [Line Items]
Vehicle finance leases	[2]	$ 93	$ 95
Borrowing margin (as a percent)		2.45%	2.45%
Variable rate basis		one-month LIBOR
Senior Secured Term Loan Facility Maturing In 2026 [Member]
Long-term debt [Line Items]
Advanced amortization payments		$ 51
Senior Secured Term Loan Facility Maturing In 2026 [Member] | Secured Debt [Member]
Long-term debt [Line Items]
Long-term debt	[3]	538	$ 593
Unamortized debt issuance costs		7	6
Unamortized original issue discount		1	1
5.125% Notes Maturing In 2024 [Member] | Notes [Member]
Long-term debt [Line Items]
Long-term debt	[4]	$ 743	$ 742
Interest rate (as a percent)		5.125%	5.125%
Unamortized debt issuance costs		$ 7	$ 8
7.45% notes maturing in 2027 [Member] | Notes [Member]
Long-term debt [Line Items]
Long-term debt	[5]	$ 169	$ 167
Interest rate (as a percent)		7.45%	7.45%	7.45%	7.45%
7.25% notes maturing in 2038 [Member] | Notes [Member]
Long-term debt [Line Items]
Long-term debt	[5]	$ 41	$ 40
Interest rate (as a percent)		7.25%	7.25%		7.25%
Notes 7.45%, And 7.25% Collectively [Member] | Notes [Member]
Long-term debt [Line Items]
Unamortized fair value adjustments related to purchase accounting		$ 26	$ 28
Other [Member]
Long-term debt [Line Items]
Long-term debt	[6]	82	98
Copesan Services, Inc. (“Copesan”) [Member] | Other [Member]
Long-term debt [Line Items]
Long-term debt		$ 81	$ 85

[1] The current portion of long-term debt consists of deferred purchase price and earnout payments on acquisitions and scheduled principal payments of long-term debt due within 12 months.

[2] We have entered into a fleet management services agreement (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 percent.

[3] As of September 30, 2020 and December 31, 2019, presented net of $7 million and $6 million in unamortized debt issuance costs, respectively, and $1 million of unamortized original issue discount in each period. On September 30, 2020, we made an advanced amortization payment of $51 million on the Term Loan B. See further discussion in Term Loan Facility below.

[4] As of September 30, 2020 and December 31, 2019, presented net of $7 million and $8 million, respectively of unamortized debt issuance costs.

[5] As of September 30, 2020 and December 31, 2019, collectively presented net of $26 million and $28 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 September 30, 2020 and December 31, 2019, includes approximately $81 million and $85 million, respectively, of future payments in connection with acquisitions.