Borrowings (Annual Maturities on Long-term Debt Outstanding) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2019	$ 0
2020	700
2021	1,200
2022	256
2023	800
Thereafter	4,525
Total maturities	7,481
Unamortized discount, net	(14)	$ (15)
Debt issuance costs	(40)	(40)
Total long-term debt	$ 7,427	$ 6,878

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