Unearned revenue liability (URL Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Insurance [Abstract]
Balance – beginning of period	$ 567	$ 503	$ 393
Deferred revenue	134	142	144
Amortization	(67)	(50)	(38)
Other (including foreign exchange)	39	(28)	4
Balance – end of period	$ 673	$ 567	$ 503