Restructuring and other (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 28	$ 253	$ 46
Employee severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other	9	37	10
Acquisition-related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	8	21
Acquisition-related costs | NYX
Restructuring Cost and Reserve [Line Items]
Restructuring and other		8	15
Contingent acquisition consideration
Restructuring Cost and Reserve [Line Items]
Restructuring and other	2	29	0
Legal and related
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	152	0
Restructuring, integration and other
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 17	$ 27	$ 15