Lease Commitments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Rental expenses for operating leases
Rental expense	$ 374	$ 377	$ 358
Sub lease rental income	(45)	(57)	(52)
Net rental expense	329	$ 320	$ 306
Future minimum rental payments under operating leases
Gross rental commitment 2019	303
Gross rental commitment 2020	253
Gross rental commitment 2021	221
Gross rental commitment 2022	182
Gross rental commitment 2023	148
Gross rental commitment thereafter	472
Total gross rental commitments	1,579
Sublease income 2019	(34)
Sublease income 2020	(30)
Sublease income 2021	(30)
Sublease income 2022	(30)
Sublease income 2023	(12)
Sublease income thereafter	(5)
Total future sublease income	(141)
Net rental commitment 2019	269
Net rental commitment 2020	223
Net rental commitment 2021	191
Net rental commitment 2022	152
Net rental commitment 2023	136
Net rental commitment thereafter	467
Total minimum payments required	$ 1,438

Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, After Year Five

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Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Year Five

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Operating Leases, Future Minimum Payments Due, Future Sublease Rentals, next twelve months

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date, net of sublease rental income, relating to leases defined as operating.

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Operating Leases, Future Minimum Payments Due, Year Two

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The total of future contractually required payments, net of sublease rental income, on leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due within the fifth year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income due within the third year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due after the fifth year from the balance sheet date on leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments, net of sublease rental income, due within the second year of the balance sheet date relating to leases defined as operating.

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Contractually required future rental payments receivable on noncancelable subleasing arrangements.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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The total amount of sublease rental income recognized during the period that reduces the entity's rent expense incurred under operating leases.

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