Reinsurance Level 4 Reinsurance Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Assumed Premiums Earned	$ 116	$ 129	$ 113
Ceded Premiums Earned	(1,539)	(1,616)	(1,801)
Life Annuity Accident and Health Insurance Product Line [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Fee Income Earned Premium and Other Life	2,434	2,659	2,877
Assumed Premiums Earned	116	129	113
Ceded Premiums Earned	(1,539)	(1,616)	(1,801)
Net Fee Income Earned Premium and Other Life	$ 1,011	$ 1,172	$ 1,189