Supplemental Cash Flow Information - Activities resulting from management of proceeds (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Net change in proceeds managed
Net change in fixed income securities	$ 0	$ 80
Net change in short-term investments	314	(709)
Operating cash flow provided (used)	314	(629)
Net change in cash	(6)	0
Net change in proceeds managed	308	(629)
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(1,829)	(1,458)
Liabilities for collateral, end of period	(1,521)	(2,087)
Operating cash flow (used) provided	$ (308)	$ 629