Summary of Significant Accounting Policies - Intangible assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 126	$ 105	$ 99
2020	109
2021	91
2022	74
2023	60
2024	45
Thereafter	64
Total amortization	443
Accumulated amortization on intangible assets	633	572
Intangible assets by type	481	713
Impairment of intangible assets (Excluding Goodwill)	$ 106
Customers relationships
Finite-Lived Intangible Assets [Line Items]
Finite-Lived intangible asset, useful life	10 years
Intangible assets by type	$ 419	530
Technology and other
Finite-Lived Intangible Assets [Line Items]
Intangible assets by type	$ 24	40
Technology-Based Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived intangible asset, useful life	5 years
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived intangible asset, useful life	7 years
Trade names and licenses
Finite-Lived Intangible Assets [Line Items]
Intangible assets by type	$ 38	$ 143