Unearned revenue liability (URL Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Insurance [Abstract]
Balance – beginning of period	$ 711	$ 673
Deferred revenue	34	34
Amortization	(18)	(18)
Other (including foreign exchange)	(8)	(9)
Balance – end of period	$ 719	$ 680