Borrowings - Interest on Debt (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Interest on Debt
Interest capitalized	$ 2	$ 3
Total interest paid and accrued	391	349
Cost of financing
Interest on Debt
Interest paid	179	182
Interest expense
Interest on Debt
Interest paid	$ 210	$ 165