Deferred revenues (Details) - USD ($) $ in Billions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred revenues	$ 1.2		$ 1.2		$ 1.4
Revenue recognized included in beginning deferred revenue	$ 0.4	$ 0.4	$ 1.2	$ 1.3