Goodwill and acquisition-related intangibles - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 4,362,000,000		$ 4,362,000,000		$ 4,362,000,000
Goodwill impairment loss			0	$ 0
Amortization of acquisition-related intangibles	$ 79,000,000	$ 80,000,000	$ 238,000,000	$ 239,000,000

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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