Securities (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Summary of AFS Securities

The following tables summarize AFS and HTM securities:

December 31, 2018 (Dollars in millions)	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
AFS securities:
U.S. Treasury	$	3,503	$	22	$	84	$	3,441
GSE	209		—		9		200
Agency MBS	20,927		15		787		20,155
States and political subdivisions	694		25		18		701
Non-agency MBS	321		184		—		505
Other	35		1		—		36
Total AFS securities	$	25,689	$	247	$	898	$	25,038
HTM securities:
U.S. Treasury	$	1,099	$	—	$	6	$	1,093
GSE	2,199		4		43		2,160
Agency MBS	17,248		27		487		16,788
States and political subdivisions	5		—		—		5
Other	1		—		—		1
Total HTM securities	$	20,552	$	31	$	536	$	20,047
December 31, 2017 (Dollars in millions)	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
AFS securities:
U.S. Treasury	$	2,368	$	—	$	77	$	2,291
GSE	187		—		8		179
Agency MBS	20,683		8		590		20,101
States and political subdivisions	1,379		37		24		1,392
Non-agency MBS	384		192		—		576
Other	8		—		—		8
Total AFS securities	$	25,009	$	237	$	699	$	24,547
HTM securities:
U.S. Treasury	$	1,098	$	8	$	—	$	1,106
GSE	2,198		11		22		2,187
Agency MBS	19,660		33		222		19,471
States and political subdivisions	28		—		—		28
Other	43		2		—		45
Total HTM securities	$	23,027	$	54	$	244	$	22,837

Summary of HTM Securities

The following tables summarize AFS and HTM securities:

December 31, 2018 (Dollars in millions)	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
AFS securities:
U.S. Treasury	$	3,503	$	22	$	84	$	3,441
GSE	209		—		9		200
Agency MBS	20,927		15		787		20,155
States and political subdivisions	694		25		18		701
Non-agency MBS	321		184		—		505
Other	35		1		—		36
Total AFS securities	$	25,689	$	247	$	898	$	25,038
HTM securities:
U.S. Treasury	$	1,099	$	—	$	6	$	1,093
GSE	2,199		4		43		2,160
Agency MBS	17,248		27		487		16,788
States and political subdivisions	5		—		—		5
Other	1		—		—		1
Total HTM securities	$	20,552	$	31	$	536	$	20,047
December 31, 2017 (Dollars in millions)	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
AFS securities:
U.S. Treasury	$	2,368	$	—	$	77	$	2,291
GSE	187		—		8		179
Agency MBS	20,683		8		590		20,101
States and political subdivisions	1,379		37		24		1,392
Non-agency MBS	384		192		—		576
Other	8		—		—		8
Total AFS securities	$	25,009	$	237	$	699	$	24,547
HTM securities:
U.S. Treasury	$	1,098	$	8	$	—	$	1,106
GSE	2,198		11		22		2,187
Agency MBS	19,660		33		222		19,471
States and political subdivisions	28		—		—		28
Other	43		2		—		45
Total HTM securities	$	23,027	$	54	$	244	$	22,837

Schedule of Amortized Cost and Estimated Fair Value by Contractual Maturity

The amortized cost and estimated fair value of the securities portfolio by contractual maturity are shown in the following table. The expected life of MBS may differ from contractual maturities because borrowers have the right to prepay the underlying mortgage loans.

	AFS				HTM
December 31, 2018 (Dollars in millions)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	425	$	424	$	1	$	1
Due after one year through five years	2,660		2,587		3,290		3,244
Due after five years through ten years	1,038		1,043		627		611
Due after ten years	21,566		20,984		16,634		16,191
Total debt securities	$	25,689	$	25,038	$	20,552	$	20,047

Schedule of Fair Values and Gross Unrealized Losses

The following tables present the fair values and gross unrealized losses of investments based on the length of time that individual securities have been in a continuous unrealized loss position:

	Less than 12 months				12 months or more				Total
December 31, 2018 (Dollars in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
AFS securities:
U.S. Treasury	$	111	$	—	$	2,121	$	84	$	2,232	$	84
GSE	3		—		176		9		179		9
Agency MBS	322		2		18,478		785		18,800		787
States and political subdivisions	100		1		288		17		388		18
Total	$	536	$	3	$	21,063	$	895	$	21,599	$	898
HTM securities:
U.S. Treasury	$	698	$	3	$	395	$	3	$	1,093	$	6
GSE	—		—		1,749		43		1,749		43
Agency MBS	264		3		14,976		484		15,240		487
Total	$	962	$	6	$	17,120	$	530	$	18,082	$	536
	Less than 12 months				12 months or more				Total
December 31, 2017 (Dollars in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
AFS securities:
U.S. Treasury	$	634	$	4	$	1,655	$	73	$	2,289	$	77
GSE	9		—		170		8		179		8
Agency MBS	5,077		64		13,920		526		18,997		590
States and political subdivisions	201		1		355		23		556		24
Total	$	5,921	$	69	$	16,100	$	630	$	22,021	$	699
HTM securities:
GSE	$	1,470	$	12	$	290	$	10	$	1,760	$	22
Agency MBS	10,880		77		4,631		145		15,511		222
Total	$	12,350	$	89	$	4,921	$	155	$	17,271	$	244