Derivative Instruments and Hedging Activities (Details - Hedge Ineffectiveness) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Fair Value Hedge, Hedging Instrument		$ 24
Fair Value Hedge, Hedged Item		(25)
Fair Value Hedge, Hedge Ineffectiveness	$ (3)	(1)
Summary of Dervative Instruments By Hedge Designation [Abstract]
Carrying Amount of Hedged Assets	12,090
Cumulative amount of basis adjustment included in total carrying amount of fair value hedges	(320)
Cumulative amount of basis adjustment included in carrying amount of discontinued fair value hedges	(215)
Closed Portfolio and Beneficial Interest Last of Layer Amortized Cost [Abstract]
Amortized Cost Basis of Closed Portfolio Last-of-Layer	910
Amount Representing Hedged Items Designated as Last-of-Layer	440
Basis Adjustment Associated with Hedged Items Designated as Last-of-Layer	$ 1
Agency Debentures [Member]
Derivative [Line Items]
Fair Value Hedge, Hedging Instrument		11
Fair Value Hedge, Hedged Item		(11)
Fair Value Hedge, Hedge Ineffectiveness		0
Agency mortgage-backed securities [Member]
Derivative [Line Items]
Fair Value Hedge, Hedging Instrument		13
Fair Value Hedge, Hedged Item		(14)
Fair Value Hedge, Hedge Ineffectiveness		$ (1)