Other-Than-Temporary Impairment Analysis Transfers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Transfers of other-than-temporarily impaired HTM securities to AFS securities	$ 1	$ 12	$ 0
Subtotal PLRMBS
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Transfers of other-than-temporarily impaired HTM securities to AFS securities	1	12
HTM Securities Transferred to AFS Securities During Period, OTTI Recognized in AOCI	0	0
HTM Transfer, Unrealized Gain (Loss)	0	0
HTM Securities Transferred to AFS Securities During Period, Fair Value	1	12
Residential Mortgage Backed Securities [Member] | Subtotal PLRMBS | Prime
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Transfers of other-than-temporarily impaired HTM securities to AFS securities	1	0
HTM Securities Transferred to AFS Securities During Period, OTTI Recognized in AOCI	0	0
HTM Transfer, Unrealized Gain (Loss)	0	0
HTM Securities Transferred to AFS Securities During Period, Fair Value	1	0
Residential Mortgage Backed Securities [Member] | Subtotal PLRMBS | Alt-A
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Transfers of other-than-temporarily impaired HTM securities to AFS securities	0	12
HTM Securities Transferred to AFS Securities During Period, OTTI Recognized in AOCI	0	0
HTM Transfer, Unrealized Gain (Loss)	0	0
HTM Securities Transferred to AFS Securities During Period, Fair Value	$ 0	$ 12