Fair value measurements Fair Value Measurements (Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation) (Details) - Level 3 - Guaranteed Minimum Income Benefit - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - Beginning of year, liabilities	$ 1,089		$ 897	$ 861
Transfers Into Level 3, liabilities	0		0	0
Transfers out of Level 3, liabilities	0		0	0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities	0		0	0
Net Realized Gains/Losses, Liabilities	(316)		202	4
Purchased, liabilities	0		0	0
Sales, liabilities	0		0	0
Settlements, liabilities	0		0	0
Balance - End of year, liabilities	745	[1]	1,089	897
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	(316)		202	4
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 0		$ 0	$ 0

[1] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.