Investments in Securities Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Available-for-sale Securities, Other-than-temporary Impairment not Recorded	$ 80	$ 52
Accumulated Other Comprehensive Income (Loss), Net of Tax, Available-for-sale Gain (Loss), Other-than-temporary Impairment Recorded	95	224
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	41	46
Accumulated other comprehensive income	216	322
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 57	$ 635	$ 733	$ 1,100