Supplemental Cash Flow Information - Net change (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net change in proceeds managed
Net change in fixed income securities	$ 259	$ (584)	$ 0
Net change in short-term investments	(255)	295	(59)
Operating cash flow provided (used)	4	(289)	(59)
Net change in cash	1	0	1
Net change in proceeds managed	5	(289)	(58)
Net change in liabilities
Liabilities for collateral, beginning of year	(1,129)	(840)	(782)
Liabilities for collateral, end of year	(1,124)	(1,129)	(840)
Operating cash flow (used) provided	$ (5)	$ 289	$ 58