Revenue from Contracts With Customers - Contract balances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Contract with Customer, Asset and Liability [Abstract]
Contract Liabilities (Current)	$ 87	$ 45	$ 45
Contract Liabilities (Noncurrent)	9	8
Increase (decrease) current contract liabilities	42
Increase (decrease) noncurrent contract liabilities	1	8
Total increase (decrease) in contract liabilities	43
Cash received on contract liabilities	254
Revenue recognized included in contract liabilities current	211
Revenue recognized from opening balance of contract liabilities	45
Revenue recognized from obligations satisfied or partially satisfied in prior periods	$ 15	$ 18