Other-Than-Temporary Impairment Analysis (OTTI Rollforward) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other than Temporary Impairment Losses, Investments [Abstract]
OTTI PLRMBS, Total accretion or amortization recognized in interest income		$ 78	$ 81	$ 93
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of the period		1,077	1,129	1,183
Additional charges on securities for which OTTI was previously recognized	[1]	11	11	16
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold and Matured	[2]	(6)	0	(1)
Accretion of yield adjustments resulting from improvement of expected cash flows that are recognized over the remaining life of the securities	[3]	(61)	(63)	(69)
Balance, end of the period		$ 1,021	$ 1,077	$ 1,129

[1] For the years ended December 31, 2019, 2018, and 2017 “securities for which OTTI was previously recognized” represents all securities that were also other-than-temporarily impaired prior to January 1, 2019, 2018, and 2017, respectively.

[2] Represents reductions related to securities having reached final maturity during the period, which therefore are no longer held by the Bank at the end of the period.

[3] The total net accretion/(amortization) associated with other-than-temporarily impaired PLRMBS (amount recognized in interest income) totaled $78, $81, and $93 for the years ended December 31, 2019, 2018, and 2017, respectively.