Investments in Marketable Securities (Tables)

12 Months Ended

Mar. 31, 2013

Investments in Marketable Securities [Abstract]

Summary of Investments in Marketable Securities

				March 31, 2013
				Amortized		Unrealized		Unrealized			Fair
(Dollars in millions)				cost		gains		losses			value
Available-for-sale securities:
	Debt instruments:
		U.S. government and agency obligations		$	101	$	3	$	-	$	104
		Municipal debt securities			14		2		-		16
		Certificates of deposit			2,040		1		-		2,041
		Commercial paper			495		-		-		495
		Foreign government debt securities			3		-		-		3
		Corporate debt securities			122		6		-		128
		Mortgage-backed securities:
			U.S. government agency		83		4		-		87
			Non-agency residential		4		1		-		5
			Non-agency commercial		50		1		-		51
		Asset-backed securities			13		-		-		13
	Equity instruments:
		Fixed income mutual funds:
			Short-term sector fund		40		3		-		43
			U.S. government sector fund		296		16		-		312
			Municipal sector fund		19		3		-		22
			Investment grade corporate sector fund		273		54		-		327
			High-yield sector fund		34		8		-		42
			Real return sector fund		284		9		-		293
			Mortgage sector fund		663		-		(15)		648
			Asset-backed securities sector fund		38		9		-		47
			Emerging market sector fund		63		3		-		66
			International sector fund		163		7		-		170
		Equity mutual fund			259		225		-		484
Total investments in marketable securities				$	5,057	$	355	$	(15)	$	5,397

Note 3 – Investments in Marketable Securities (Continued)
					March 31, 2012
				Amortized		Unrealized		Unrealized			Fair
(Dollars in millions)				cost		gains		losses			value
Available-for-sale securities:
	Debt instruments:
		U.S. government and agency obligations		$	108	$	1	$	(1)	$	108
		Municipal debt securities			17		3		-		20
		Certificates of deposit			1,341		-		-		1,341
		Commercial paper			633		-		-		633
		Foreign government debt securities			3		-		-		3
		Corporate debt securities			100		7		-		107
		Mortgage-backed securities:
			U.S. government agency		100		5		-		105
			Non-agency residential		7		1		-		8
			Non-agency commercial		25		1		-		26
		Asset-backed securities			13		-		-		13
	Equity instruments:
		Fixed income mutual funds:
			Short-term sector fund		39		1		-		40
			U.S. government sector fund		319		-		(6)		313
			Municipal sector fund		19		2		-		21
			Investment grade corporate sector fund		261		37		-		298
			High-yield sector fund		31		6		-		37
			Real return sector fund		228		3		-		231
			Mortgage sector fund		651		-		(12)		639
			Asset-backed securities sector fund		37		4		-		41
			Emerging market sector fund		60		2		-		62
			International sector fund		143		19		-		162
		Equity mutual fund			268		183		-		451
Total investments in marketable securities				$	4,403	$	275	$	(19)	$	4,659

Summary of the aging of fair value and gross unrealized losses for AFS securities

		Less than 12 months as of
		March 31, 2013					March 31, 2012
		Fair		Unrealized		Fair		Unrealized
(Dollars in millions)		value		losses		value		losses
Available-for-sale securities:
Debt instruments:
	U.S. government and agency obligations	$	-	$	-	$	68	$	(1)
Equity instruments:
	U.S. government sector fund		-		-		237		(2)
	Mortgage sector fund		532		(12)		639		(12)
Total investments in marketable securities		$	532	$	(12)	$	944	$	(15)

Schedule of realized gains and losses on sales from AFS

		Years ended March 31,
(Dollars in millions)		2013		2012		2011
Available-for-sale securities:
Realized gains on sales	$	23	$	16	$	70
Realized losses on sales	$	2	$	41	$	23

Summary of Contractual Maturities of Available-for-Sale Securities

		Due in 1 Year or				Due after 1 Year				Due after 5 Years
		Less				through 5 Years				through 10 Years				Due after 10 Years				Total
(Dollars in millions)		Amount		Yield		Amount		Yield		Amount		Yield		Amount		Yield		Amount		Yield
Fair Value of Available-for-Sale Securities:
Debt instruments:
U.S. government and
	agency obligations	$	12	0.11	%	$	46	1.44	%	$	41	1.78	%	$	5	1.84	%	$	104	1.52	%
Municipal debt securities			2	1.33			-	0.00			2	5.54			12	5.76			16	5.33
Certificates of deposit			2,041	0.56			-	0.00			-	0.00			-	0.00			2,041	0.56
Commercial paper			495	0.13			-	0.00			-	0.00			-	0.00			495	0.13
Foreign government debt
	securities		-	0.00			3	2.93			-	0.00			-	0.00			3	2.93
Corporate debt
	securities		10	4.75			51	4.52			56	4.80			11	6.09			128	4.60
Mortgage-backed securities:
	U.S. government agency		-	0.00			-	-			5	4.11			82	3.49			87	3.53
	Non-agency residential		-	0.00			-	0.00			-	0.00			5	10.92			5	10.92
	Non-agency commercial		-	0.00			4	3.56			2	1.23			45	3.65			51	3.44
Asset-backed securities			-	0.00			-	0.00			7	1.10			6	1.68			13	1.42
Debt instruments total			2,560	0.50			104	3.09			113	3.41			166	3.99			2,943	0.89
Equity instruments:
Fixed income mutual funds																			1,970	5.27
Equity mutual funds																			484	3.85
Equity instruments total			-				-				-				-				2,454	4.99
Total fair value		$	2,560	0.50	%	$	104	3.09	%	$	113	3.41	%	$	166	3.99	%	$	5,397	2.75	%
Total amortized cost		$	2,559			$	100			$	107			$	160			$	5,057