Supplemental Cash Flow Information - Activities resulting from management of proceeds (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net change in proceeds managed
Net change in short-term investments	$ (183)	$ 370
Operating cash flow (used) provided	(183)	370
Net change in cash	1	0
Net change in proceeds managed	(182)	370
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(914)	(1,298)
Liabilities for collateral, end of period	(1,096)	(928)
Operating cash flow provided (used)	$ 182	$ (370)