Supplemental Cash Flow Information - Activities resulting from management of proceeds (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Net change in proceeds managed
Net change in fixed income securities	$ 0	$ 80
Net change in short-term investments	456	(493)
Operating cash flow provided (used)	456	(413)
Net change in cash	(8)	0
Net change in proceeds managed	448	(413)
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(1,829)	(1,458)
Liabilities for collateral, end of period	(1,381)	(1,871)
Operating cash flow (used) provided	$ (448)	$ 413