Investments (Variable Interest Entities - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Proceeds From Securitizations of Loans Held-for-Investment, Carry Value	$ 451	$ 319
Proceeds from Securitizations of Loans Held-for-investment	478	339
Gain (Loss) on Securitization of Financial Assets	27	20
Financial or other support to investees designated as VIEs	0	0	$ 0
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds In Period	98	52
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 61,057	$ 60,429