Borrowings - Interest on Debt (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Interest on Debt
Interest capitalized	$ 2	$ 5
Total interest paid and accrued	388	449
Cost of financing
Interest on Debt
Interest paid	106	119
Interest expense
Interest on Debt
Interest paid	$ 280	$ 326