Unearned revenue liability (URL Rollforward) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Insurance [Abstract]
Balance – beginning of period	$ 712	$ 604	$ 673	$ 567
Deferred revenue	106	96
Amortization	(54)	(44)
Other (including foreign exchange)	(13)	(15)
Balance – end of period	$ 712	$ 604	$ 673	$ 567