Contingencies (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Self Insured Property And Casualty Reserves [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 84	$ 98
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease)	11	27
Payments	(29)	(41)
Ending balance	66	$ 84
Guarantee of Indebtedness of Others
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Loss contingency, amount of guarantee	$ 10