Intangible Assets (VOBA) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
VOBA Roll Forward
VOBA balance, beginning of year	$ 355	$ 395	$ 466
Amortization of Value of Business Acquired (VOBA)	(35)	(41)	(42)
VOBA Foreign exchange revaluation	6	1	(29)
VOBA balance, end of year	326	$ 355	$ 395
Present Value of Future Insurance Profits, Amortization Expense, Next Five Years [Abstract]
2018, VOBA	32
2019, VOBA	27
2020, VOBA	25
2021, VOBA	22
2022, VOBA	20
Total, VOBA	$ 126