Supplemental Cash Flow Information - Activities resulting from management of proceeds (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net change in proceeds managed
Net change in fixed income securities	$ 0	$ 60
Net change in short-term investments	538	(575)
Operating cash flow provided (used)	538	(515)
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(1,829)	(1,458)
Liabilities for collateral, end of period	(1,291)	(1,973)
Operating cash flow (used) provided	$ (538)	$ 515