Revenue - Disaggregation of revenue on geographic location of customers (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue
Revenues	$ 410	$ 413	$ 412	$ 431	$ 418	$ 433	$ 487	$ 466	$ 1,666	$ 1,804	$ 1,257
U.S.
Revenue
Revenues									1,240	1,238	698
Asia
Revenue
Revenues									161	213	228
South America
Revenue
Revenues									97	133	16
Europe
Revenue
Revenues									69	54	127
Middle East
Revenue
Revenues									57	90	41
Australia
Revenue
Revenues									22	17	22
Canada
Revenue
Revenues									10	49	123
Other
Revenue
Revenues									$ 10	$ 10	$ 2