Insurance (Obligations Under Funding Agreements - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Funding agreements issued to certain SPEs	$ 0	$ 1,400	$ 13,000
Funding agreements repaid to certain SPEs	6	3,400	$ 14,400
Outstanding funding agreements to certain SPEs	141	127
Federal Home Loan Bank Stock	$ 71	$ 75