Securities (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Summary of AFS Securities

	Amortized Cost		Gross Unrealized				Fair Value
December 31, 2016			Gains		Losses
	(Dollars in millions)
AFS securities:
U.S. Treasury	$	2,669	$	2	$	84	$	2,587
GSE	190		—		10		180
Agency MBS	21,819		13		568		21,264
States and political subdivisions	2,198		56		49		2,205
Non-agency MBS	446		233		—		679
Other	11		—		—		11
Total AFS securities	$	27,333	$	304	$	711	$	26,926
HTM securities:
U.S. Treasury	$	1,098	$	20	$	—	$	1,118
GSE	2,197		14		30		2,181
Agency MBS	13,225		40		180		13,085
States and political subdivisions	110		—		—		110
Other	50		2		—		52
Total HTM securities	$	16,680	$	76	$	210	$	16,546

	Amortized Cost		Gross Unrealized				Fair Value
December 31, 2015			Gains		Losses
	(Dollars in millions)
AFS securities:
U.S. Treasury	$	1,836	$	2	$	6	$	1,832
GSE	51		—		—		51
Agency MBS	20,463		22		439		20,046
States and political subdivisions	2,312		103		40		2,375
Non-agency MBS	683		306		—		989
Other	4		—		—		4
Total AFS securities	$	25,349	$	433	$	485	$	25,297
HTM securities:
U.S. Treasury	$	1,097	$	22	$	—	$	1,119
GSE	5,045		16		98		4,963
Agency MBS	12,267		70		22		12,315
States and political subdivisions	63		—		—		63
Other	58		2		1		59
Total HTM securities	$	18,530	$	110	$	121	$	18,519

Summary of HTM Securities

	Amortized Cost		Gross Unrealized				Fair Value
December 31, 2016			Gains		Losses
	(Dollars in millions)
AFS securities:
U.S. Treasury	$	2,669	$	2	$	84	$	2,587
GSE	190		—		10		180
Agency MBS	21,819		13		568		21,264
States and political subdivisions	2,198		56		49		2,205
Non-agency MBS	446		233		—		679
Other	11		—		—		11
Total AFS securities	$	27,333	$	304	$	711	$	26,926
HTM securities:
U.S. Treasury	$	1,098	$	20	$	—	$	1,118
GSE	2,197		14		30		2,181
Agency MBS	13,225		40		180		13,085
States and political subdivisions	110		—		—		110
Other	50		2		—		52
Total HTM securities	$	16,680	$	76	$	210	$	16,546

	Amortized Cost		Gross Unrealized				Fair Value
December 31, 2015			Gains		Losses
	(Dollars in millions)
AFS securities:
U.S. Treasury	$	1,836	$	2	$	6	$	1,832
GSE	51		—		—		51
Agency MBS	20,463		22		439		20,046
States and political subdivisions	2,312		103		40		2,375
Non-agency MBS	683		306		—		989
Other	4		—		—		4
Total AFS securities	$	25,349	$	433	$	485	$	25,297
HTM securities:
U.S. Treasury	$	1,097	$	22	$	—	$	1,119
GSE	5,045		16		98		4,963
Agency MBS	12,267		70		22		12,315
States and political subdivisions	63		—		—		63
Other	58		2		1		59
Total HTM securities	$	18,530	$	110	$	121	$	18,519

Schedule of Credit Losses on Securities with OTTI

The following table reflects changes in credit losses on securities with OTTI where a portion of the unrealized loss was recognized in OCI. Assets acquired from the FDIC were excluded from this table prior to the termination of the loss share agreements.

	Year Ended December 31,
	2016			2015			2014
	(Dollars in millions)
Balance at beginning of period	$	42		$	64		$	78
Credit losses on securities without previous OTTI	—			—			6
Credit losses on securities for which OTTI was previously recognized	—			4			—
Reductions for securities sold/settled during the period	(21		)	(22		)	(17		)
Credit recoveries through yield	(1		)	(4		)	(3		)
Included as a result of loss share termination	1			—			—
Balance at end of period	$	21		$	42		$	64

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 with or without prepayment penalties.

	AFS				HTM
December 31, 2016	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Dollars in millions)
Due in one year or less	$	275	$	275	$	—	$	—
Due after one year through five years	1,013		1,018		1,683		1,703
Due after five years through ten years	2,670		2,580		1,688		1,672
Due after ten years	23,375		23,053		13,309		13,171
Total debt securities	$	27,333	$	26,926	$	16,680	$	16,546

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, 2016	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(Dollars in millions)
AFS securities:
U.S. Treasury	$	2,014	$	84	$	—	$	—	$	2,014	$	84
GSE	180		10		—		—		180		10
Agency MBS	14,842		342		5,138		226		19,980		568
States and political subdivisions	365		7		314		42		679		49
Total	$	17,401	$	443	$	5,452	$	268	$	22,853	$	711
HTM securities:
GSE	$	1,762	$	30	$	—	$	—	$	1,762	$	30
Agency MBS	7,717		178		305		2		8,022		180
Total	$	9,479	$	208	$	305	$	2	$	9,784	$	210

	Less than 12 months				12 months or more				Total
December 31, 2015	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(Dollars in millions)
AFS securities:
U.S. Treasury	$	1,211	$	6	$	—	$	—	$	1,211	$	6
Agency MBS	12,052		199		5,576		240		17,628		439
States and political subdivisions	64		1		329		39		393		40
Total	$	13,327	$	206	$	5,905	$	279	$	19,232	$	485
HTM securities:
GSE	$	2,307	$	41	$	1,743	$	57	$	4,050	$	98
Agency MBS	3,992		21		124		1		4,116		22
Other	56		1		—		—		56		1
Total	$	6,355	$	63	$	1,867	$	58	$	8,222	$	121