Securities (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses, and Fair Values of Securities

At December 31, 2016 and 2015, the amortized cost, gross unrealized gains, gross unrealized losses, and fair values of securities available for sale are presented below.

	December 31, 2016
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Asset Liability Management securities:
U.S. Treasury	$	2,625	$	1	$	121	$	2,505
Residential mortgage-backed securities:
U.S. government agency and government-sponsored agencies	6,814		3		122		6,695
Privately issued	333		1		7		327
Privately issued - commercial mortgage-backed securities	666		4		6		664
Collateralized loan obligations	2,219		4		5		2,218
Other	7		—		—		7
Asset Liability Management securities	12,664		13		261		12,416
Other debt securities:
Direct bank purchase bonds	1,601		41		29		1,613
Other	108		—		1		107
Equity securities	5		—		—		5
Total securities available for sale	$	14,378	$	54	$	291	$	14,141

	December 31, 2015
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Asset Liability Management securities:
U.S. Treasury	$	596	$	1	$	3	$	594
Residential mortgage-backed securities:
U.S. government agency and government-sponsored agencies	7,298		1		98		7,201
Privately issued	150		2		1		151
Privately issued - commercial mortgage-backed securities	1,566		5		25		1,546
Collateralized loan obligations	3,266		1		34		3,233
Other	7		—		—		7
Asset Liability Management securities	12,883		10		161		12,732
Other debt securities:
Direct bank purchase bonds	1,549		45		22		1,572
Other	47		—		—		47
Equity securities	6		2		—		8
Total securities available for sale	$	14,485	$	57	$	183	$	14,359

Securities in Unrealized Loss Position

The Company's securities available for sale with a continuous unrealized loss position at December 31, 2016 and 2015 are shown below, identified for periods less than 12 months and 12 months or more.

	December 31, 2016
	Less than 12 months				12 months or more				Total
(Dollars in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Asset Liability Management securities:
U.S. Treasury	$	2,257	$	121	$	—	$	—	$	2,257	$	121
Residential mortgage-backed securities:
U.S. government agency and government-sponsored agencies	5,501		113		667		9		6,168		122
Privately issued	249		6		29		1		278		7
Privately issued - commercial mortgage-backed securities	415		6		11		—		426		6
Collateralized loan obligations	75		—		1,077		5		1,152		5
Other	—		—		1		—		1		—
Asset Liability Management securities	8,497		246		1,785		15		10,282		261
Other debt securities:
Direct bank purchase bonds	386		12		499		17		885		29
Other	36		1		—		—		36		1
Equity securities	—		—		5		—		5		—
Total securities available for sale	$	8,919	$	259	$	2,289	$	32	$	11,208	$	291

	December 31, 2015
	Less than 12 months				12 months or more				Total
(Dollars in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Asset Liability Management securities:
U.S. Treasury	$	295	$	3	$	—	$	—	$	295	$	3
Residential mortgage-backed securities:
U.S. government agency and government-sponsored agencies	4,692		57		2,278		41		6,970		98
Privately issued	39		—		38		1		77		1
Privately issued - commercial mortgage-backed securities	1,154		24		65		1		1,219		25
Collateralized loan obligations	1,497		11		1,290		23		2,787		34
Asset Liability Management securities	7,677		95		3,671		66		11,348		161
Other debt securities:
Direct bank purchase bonds	157		4		686		18		843		22
Other	2		—		—		—		2		—
Equity securities	—		—		5		—		5		—
Total securities available for sale	$	7,836	$	99	$	4,362	$	84	$	12,198	$	183

The Company's securities held to maturity with a continuous unrealized loss position at December 31, 2016 and 2015 are shown below, separately for periods less than 12 months and 12 months or more.

	December 31, 2016
	Less than 12 months						12 months or more						Total
			Unrealized Losses						Unrealized Losses						Unrealized Losses
(Dollars in millions)	Fair Value		Recognized in OCI		Not Recognized in OCI		Fair Value		Recognized in OCI		Not Recognized in OCI		Fair Value		Recognized in OCI		Not Recognized in OCI
U.S. Treasury	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—
U.S. government-sponsored agencies	—		—		—		—		—		—		—		—		—
U.S. government agency and government-sponsored agencies—residential mortgage backed securities	4,492		—		92		1,386		41		4		5,878		41		96
U.S. government agency and government-sponsored agencies - commercial mortgage-backed securities	111		—		1		1,448		63		6		1,559		63		7
Total securities held to maturity	$	4,603	$	—	$	93	$	2,834	$	104	$	10	$	7,437	$	104	$	103

	December 31, 2015
	Less than 12 months						12 months or more						Total
			Unrealized Losses						Unrealized Losses						Unrealized Losses
(Dollars in millions)	Fair Value		Recognized in OCI		Not Recognized in OCI		Fair Value		Recognized in OCI		Not Recognized in OCI		Fair Value		Recognized in OCI		Not Recognized in OCI
U.S. government-sponsored agencies	$	196	$	—	$	4	$	—	$	—	$	—	$	196	$	—	$	4
U.S. government agency and government-sponsored agencies - residential mortgage-backed securities	3,297		—		39		1,705		53		2		5,002		53		41
U.S. government agency and government-sponsored agencies - commercial mortgage-backed securities	197		—		1		1,428		73		4		1,625		73		5
Total securities held to maturity	$	3,690	$	—	$	44	$	3,133	$	126	$	6	$	6,823	$	126	$	50

Debt Securities by Contractual Maturity

The carrying amount and fair value of securities held to maturity by contractual maturity are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to prepay obligations with or without prepayment penalties.

	December 31, 2016
	Over One Year Through Five Years				Over Five Years Through Ten Years				Over Ten Years				Total
(Dollars in millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
U.S. Treasury	$	492	$	497	$	—	$	—	$	—	$	—	$	492	$	497
U.S. government agency and government-sponsored agencies - residential mortgage-backed securities	50		50		109		111		8,104		8,040		8,263		8,201
U.S. government agency and government-sponsored agencies - commercial mortgage-backed securities	49		50		806		838		727		730		1,582		1,618
Total securities held to maturity	$	591	$	597	$	915	$	949	$	8,831	$	8,770	$	10,337	$	10,316

The fair value of debt securities available for sale by contractual maturity are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to prepay obligations with or without prepayment penalties.

	December 31, 2016
(Dollars in millions)	One Year or Less		Over One Year Through Five Years		Over Five Years Through Ten Years		Over Ten Years		Total Fair Value
Asset Liability Management securities:
U.S. Treasury	$	—	$	345	$	2,160	$	—	$	2,505
Residential mortgage-backed securities:
U.S. government agency and government-sponsored agencies	—		11		324		6,360		6,695
Privately issued	—		1		—		326		327
Privately issued - commercial mortgage-backed securities	—		—		—		664		664
Collateralized loan obligations	—		—		1,369		849		2,218
Other	1		1		5		—		7
Asset Liability Management securities	1		358		3,858		8,199		12,416
Other debt securities:
Direct bank purchase bonds	4		369		816		424		1,613
Other	—		82		—		25		107
Total debt securities available for sale	$	5	$	809	$	4,674	$	8,648	$	14,136

Proceeds from Sales of Securities Available for Sale and Gross Realized Gains and Losses

The gross realized gains and losses from sales of available for sale securities for the years ended December 31, 2016, 2015 and 2014 are shown below. The specific identification method is used to calculate realized gains and losses on sales.

	For the Year Ended December 31,
(Dollars in millions)	2016		2015		2014
Gross realized gains	$	69	$	20	$	18
Gross realized losses	—		1		—

Schedule of Held to Maturity Securities Recognized and Not Recognized in Other Comprehensive Income (OCI) and Fair Values

At December 31, 2016 and 2015, the amortized cost, gross unrealized gains and losses recognized in OCI, carrying amount, gross unrealized gains and losses not recognized in OCI, and fair values of securities held to maturity are presented below. Management has asserted the positive intent and ability to hold these securities to maturity.

	December 31, 2016
			Recognized in OCI						Not Recognized in OCI
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Carrying Amount		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasury	$	492	$	—	$	—	$	492	$	5	$	—	$	497
U.S. government agency and government-sponsored agencies - residential mortgage-backed securities	8,301		3		41		8,263		34		96		8,201
U.S. government agency and government-sponsored agencies - commercial mortgage-backed securities	1,645		—		63		1,582		43		7		1,618
Total securities held to maturity	$	10,438	$	3	$	104	$	10,337	$	82	$	103	$	10,316

	December 31, 2015
			Recognized in OCI						Not Recognized in OCI
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Carrying Amount		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasury	$	489	$	—	$	—	$	489	$	4	$	—	$	493
U.S. government-sponsored agencies	220		—		—		220		—		4		216
U.S. government agency and government-sponsored agencies - residential mortgage-backed securities	7,831		4		53		7,782		49		41		7,790
U.S. government agency and government-sponsored agencies - commercial mortgage-backed securities	1,740		—		73		1,667		46		5		1,708
Total securities held to maturity	$	10,280	$	4	$	126	$	10,158	$	99	$	50	$	10,207