Intangible Assets (Components Of Intangible Assets) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Goodwill		$ 964	$ 970
Amortized Intangible Assets:		145	143
Accumulated Amortization		61	51
Net Carrying Amount		84	92
Customer Lists [Member]
Intangible Assets [Line Items]
Amortized Intangible Assets:	[1]	75	74
Accumulated Amortization	[1]	25	19
Net Carrying Amount	[1]	50	55
Management Agreement
Intangible Assets [Line Items]
Amortized Intangible Assets:	[2]	53	52
Accumulated Amortization	[2]	31	27
Net Carrying Amount	[2]	22	25
Trademarks
Intangible Assets [Line Items]
Amortized Intangible Assets:	[3]	8	8
Accumulated Amortization	[3]	5	4
Net Carrying Amount	[3]	3	4
Other Intangible Assets
Intangible Assets [Line Items]
Amortized Intangible Assets:	[4]	9	9
Accumulated Amortization	[4]	0	1
Net Carrying Amount	[4]	$ 9	8
Minimum | Customer Lists [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		4 years
Minimum | Management Agreement
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		10 years
Minimum | Trademarks
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		7 years
Minimum | Customer Lists And Business Contracts [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		10 years
Maximum | Customer Lists [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		15 years
Maximum | Management Agreement
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		25 years
Maximum | Trademarks
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		8 years
Maximum | Customer Lists And Business Contracts [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		69 years
Weighted Average [Member] | Customer Lists [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		13 years
Weighted Average [Member] | Management Agreement
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		17 years
Weighted Average [Member] | Trademarks
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		7 years
Weighted Average [Member] | Customer Lists And Business Contracts [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		57 years
Trademarks
Intangible Assets [Line Items]
Unamortizable trademarks	[5]	$ 47	$ 51

[1] Amortized between 4 to 15 years with a weighted average life of 13 years.

[2] Amortized between 10 to 25 years with a weighted average life of 17 years

[3] Amortized between 7 to 8 years with a weighted average life of 7 years.

[4] Includes business contracts, which are amortized between 10 to 69 years with a weighted average life to 57 years.

[5] Comprised of trademarks that the Company has acquired that are expected to generate future cash flows for an indefinite period of time.