Securities Available for Sale (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]



	December 31, 2017
(Dollars in millions)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury securities		$4,361		$2		$32		$4,331
Federal agency securities	257		3		1		259
U.S. states and political subdivisions	618		7		8		617
MBS - agency residential	22,616		222		134		22,704
MBS - agency commercial	2,121		3		38		2,086
MBS - non-agency residential	55		4		—		59
MBS - non-agency commercial	862		7		3		866
ABS	6		2		—		8
Corporate and other debt securities	17		—		—		17
Other equity securities ¹	472		—		3		469
Total securities AFS		$31,385		$250		$219		$31,416

	December 31, 2016
(Dollars in millions)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. Treasury securities		$5,486		$5		$86		$5,405
Federal agency securities	310		5		2		313
U.S. states and political subdivisions	279		5		5		279
MBS - agency residential	22,379		311		254		22,436
MBS - agency commercial	1,263		2		39		1,226
MBS - non-agency residential	71		3		—		74
MBS - non-agency commercial	257		—		5		252
ABS	8		2		—		10
Corporate and other debt securities	34		1		—		35
Other equity securities ¹	642		1		1		642
Total securities AFS		$30,729		$335		$392		$30,672

¹ At December 31, 2017, the fair value of other equity securities was comprised of the following: $15 million of FHLB of Atlanta stock, $403 million of Federal Reserve Bank of Atlanta stock, $49 million of mutual fund investments, and $2 million of other.

At December 31, 2016, the fair value of other equity securities was comprised of the following: $132 million of FHLB of Atlanta stock, $402 million of Federal Reserve Bank of Atlanta stock, $102 million of mutual fund investments, and $6 million of other.

Investment Income [Table Text Block]

The following table presents interest and dividends on securities AFS:



	Year Ended December 31
(Dollars in millions)	2017		2016		2015
Taxable interest		$743		$630		$552
Tax-exempt interest	13		6		6
Dividends	18		15		35
Total interest and dividends on securities AFS		$774		$651		$593

Amortized Cost and Fair Value of Investments in Debt Securities by Estimated Average Life

The following table presents the amortized cost, fair value, and weighted average yield of investments in debt securities AFS at December 31, 2017, by remaining contractual maturity, with the exception of MBS and ABS, which are based on estimated average life. Receipt of cash flows may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalties.



	Distribution of Remaining Maturities
(Dollars in millions)	Due in 1 Year or Less			Due After 1 Year through 5 Years			Due After 5 Years through 10 Years			Due After 10 Years			Total
Amortized Cost:
U.S. Treasury securities		$—			$2,322			$2,039			$—			$4,361
Federal agency securities	121			46			4			86			257
U.S. states and political subdivisions	6			49			149			414			618
MBS - agency residential	2,686			7,937			11,781			212			22,616
MBS - agency commercial	—			315			1,547			259			2,121
MBS - non-agency residential	—			55			—			—			55
MBS - non-agency commercial	—			12			813			37			862
ABS	—			6			—			—			6
Corporate and other debt securities	7			10			—			—			17
Total debt securities AFS		$2,820			$10,752			$16,333			$1,008			$30,913
Fair Value:
U.S. Treasury securities		$—			$2,305			$2,026			$—			$4,331
Federal agency securities	123			47			4			85			259
U.S. states and political subdivisions	6			52			153			406			617
MBS - agency residential	2,748			7,980			11,763			213			22,704
MBS - agency commercial	—			308			1,525			253			2,086
MBS - non-agency residential	—			59			—			—			59
MBS - non-agency commercial	—			12			816			38			866
ABS	—			8			—			—			8
Corporate and other debt securities	7			10			—			—			17
Total debt securities AFS		$2,884			$10,781			$16,287			$995			$30,947
Weighted average yield ¹	3.36		%	2.34		%	2.81		%	3.23		%	2.71		%

¹Weighted average yields are based on amortized cost and presented on an FTE basis.

Securities in a Continuous Unrealized Loss Position

Securities AFS in an unrealized loss position at period end are presented in the following tables:



	December 31, 2017
	Less than twelve months				Twelve months or longer				Total
(Dollars in millions)	Fair Value		Unrealized Losses ²		Fair Value		Unrealized Losses ²		Fair Value		Unrealized Losses ²
Temporarily impaired securities AFS:
U.S. Treasury securities		$1,993		$12		$841		$20		$2,834		$32
Federal agency securities	23		—		60		1		83		1
U.S. states and political subdivisions	267		3		114		5		381		8
MBS - agency residential	8,095		38		4,708		96		12,803		134
MBS - agency commercial	887		9		915		29		1,802		38
MBS - non-agency commercial	134		1		93		2		227		3
ABS	—		—		4		—		4		—
Corporate and other debt securities	10		—		—		—		10		—
Other equity securities	—		—		2		3		2		3
Total temporarily impaired securities AFS	11,409		63		6,737		156		18,146		219
OTTI securities AFS ¹:
ABS	—		—		1		—		1		—
Total OTTI securities AFS	—		—		1		—		1		—
Total impaired securities AFS		$11,409		$63		$6,738		$156		$18,147		$219

¹OTTI securities AFS are impaired securities for which OTTI credit losses have been previously recognized in earnings.

²Unrealized losses less than $0.5 million are presented as zero within the table.



	December 31, 2016
	Less than twelve months				Twelve months or longer				Total
(Dollars in millions)	Fair Value		Unrealized Losses ²		Fair Value		Unrealized Losses ²		Fair Value		Unrealized Losses ²
Temporarily impaired securities AFS:
U.S. Treasury securities		$4,380		$86		$—		$—		$4,380		$86
Federal agency securities	96		2		3		—		99		2
U.S. states and political subdivisions	149		5		—		—		149		5
MBS - agency residential	13,505		247		436		7		13,941		254
MBS - agency commercial	1,117		38		15		1		1,132		39
MBS - non-agency commercial	184		5		—		—		184		5
ABS	—		—		5		—		5		—
Corporate and other debt securities	12		—		—		—		12		—
Other equity securities	—		—		4		1		4		1
Total temporarily impaired securities AFS	19,443		383		463		9		19,906		392
OTTI securities AFS ¹:
MBS - non-agency residential	16		—		—		—		16		—
ABS	—		—		1		—		1		—
Total OTTI securities AFS	16		—		1		—		17		—
Total impaired securities AFS		$19,459		$383		$464		$9		$19,923		$392

¹OTTI securities AFS are impaired securities for which OTTI credit losses have been previously recognized in earnings.

²Unrealized losses less than $0.5 million are presented as zero within the table.

Realized Gain (Loss) on Investments [Table Text Block]



	Year Ended December 31
(Dollars in millions)	2017			2016		2015
Gross realized gains		$3			$4		$25
Gross realized losses	(110		)	—		(3		)
OTTI credit losses recognized in earnings	(1		)	—		(1		)
Net securities (losses)/gains		($108	)		$4		$21

Measurement of Investment Credit Loss Assumptions [Table Text Block]

The following table presents a summary of the significant inputs used in determining the measurement of OTTI credit losses recognized in earnings for non-agency MBS for the years ended December 31:



	2017 ¹	2016 ²	2015 ¹
Default rate	3%	N/A	9%
Prepayment rate	19%	N/A	13%
Loss severity	41%	N/A	56%

¹ OTTI credit losses recognized in earnings relate to one non-agency MBS with a fair value of $12 million and $20 million at December 31, 2017 and 2015, respectively.

²"N/A" - Not applicable as there were no OTTI credit losses recognized in earnings for the year ended December 31, 2016.

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

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