Deferred Policy Acquisition Costs, Value of Business Acquired and Other Policy-Related Intangibles (Deferred Sales Inducements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
DSI:
Balance at January 1,	$ 241	$ 242	$ 224
Capitalization	16	22	28
Amortization	(29)	(23)	(30)
Unrealized investment gains (losses)	(6)	0	20
Effect of foreign currency translation	(2)	0	0
Balance at December 31,	$ 220	$ 241	$ 242