Goodwill and Other Intangible Assets (Other Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Total	$ 648	$ 895
Amortization expense	250	290	$ 213
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2021	206
2022	161
2023	117
2024	75
2025	50
Thereafter	39
Total	$ 648	$ 895
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Amortization Period	35 months	43 months
Gross Carrying Amount	$ 12	$ 24
Accumulated Amortization	6	14
Total	6	10
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	$ 6	$ 10
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Amortization Period	6 years	7 years
Gross Carrying Amount	$ 2,252	$ 2,246
Accumulated Amortization	1,614	1,364
Total	638	882
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	$ 638	$ 882
Trade names and associated trademarks
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Amortization Period	4 years	4 years
Gross Carrying Amount	$ 8	$ 5
Accumulated Amortization	4	2
Total	4	3
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	$ 4	$ 3