Investments in Marketable Securities (Tables)

12 Months Ended

Mar. 31, 2017

Marketable Securities [Abstract]

Summary of Investments in Marketable Securities

The amortized cost and estimated fair value of investments in marketable securities and related unrealized gains and losses were as follows:

	March 31, 2017
	Amortized		Unrealized		Unrealized			Fair
	cost		gains		losses			value
Available-for-sale securities:
Debt instruments:
U.S. government and agency obligations	$	2,314	$	1	$	(7	)	$	2,308
Municipal debt securities		10		1	-				11
Certificates of deposit		755	-		-				755
Corporate debt securities		368		2		(1	)		369
Mortgage-backed securities:
U.S. government agency		45		1		(1	)		45
Non-agency residential		2	-		-				2
Non-agency commercial		37		1		(1	)		37
Asset-backed securities		31	-		-				31
Equity instruments:
Fixed income mutual funds:
Short-term floating NAV fund II		39	-		-				39
U.S. government sector fund		389	-		-				389
Municipal sector fund		20	-		-				20
Investment grade corporate sector fund		252		9	-				261
High-yield sector fund		83		6	-				89
Real return sector fund		147		5	-				152
Mortgage sector fund		390		2	-				392
Asset-backed securities sector fund		140		10	-				150
Emerging market sector fund		105		7	-				112
International sector fund		136	-		-				136
Total return bond funds		389		5	-				394
Total investments in marketable securities	$	5,652	$	50	$	(10	)	$	5,692

Note 3 – Investments in Marketable Securities (Continued)

	March 31, 2016
	Amortized		Unrealized		Unrealized			Fair
	cost		gains		losses			value
Available-for-sale securities:
Debt instruments:
U.S. government and agency obligations	$	2,833	$	3	$	(1	)	$	2,835
Municipal debt securities		10		1		-			11
Certificates of deposit		500		-		-			500
Commercial paper		50		-		-			50
Corporate debt securities		482		7		(2	)		487
Mortgage-backed securities:
U.S. government agency		57		2		-			59
Non-agency residential		2		1		-			3
Non-agency commercial		42		1		(1	)		42
Asset-backed securities		38		-		(1	)		37
Equity instruments:
Fixed income mutual funds:
Short-term floating NAV fund II		178		-		-			178
U.S. government sector fund		353		6		(1	)		358
Municipal sector fund		19		-		-			19
Investment grade corporate sector fund		243		8		(5	)		246
High-yield sector fund		67		-		(1	)		66
Real return sector fund		201		11		-			212
Mortgage sector fund		297		5		-			302
Asset-backed securities sector fund		117		8		(1	)		124
Emerging market sector fund		101		1		-			102
International sector fund		145		-		(5	)		140
Total return bond funds		376		4		-			380
Equity mutual fund		162		227		-			389
Total investments in marketable securities	$	6,273	$	285	$	(18	)	$	6,540

Schedule of Realized Gains and Losses on Sales from AFS Presented in Our Consolidated Statement of Income

The following table represents realized gains and losses on our available-for-sale securities presented in our Consolidated Statements of Income:

	Years Ended March 31,
	2017			2016			2015
Available-for-sale securities:
Realized gains on sales	$	251		$	59		$	71
Realized losses on sales	$	(1	)	$	(3	)	$	(1	)
Other-than-temporary impairment	$	(24	)	$	(50	)	$	-

Summary of Contractual Maturities of Available-for-Sale Securities

The amortized cost, fair value and contractual maturities of available-for-sale debt instruments are summarized in the following table.  Actual maturities may differ from contractual maturities because certain borrowers have the right to call or prepay certain obligations.

	March 31, 2017
	AmortizedCost		Fair Value
Available-for-sale debt instruments:
Due within 1 year	$	2,303	$	2,302
Due after 1 year through 5 years		926		926
Due after 5 years through 10 years		126		125
Due after 10 years		92		90
Mortgage-backed and asset-backed securities1		115		115
Total	$	3,562	$	3,558

¹ Mortgage-backed and asset-backed securities are shown separately from other maturity groupings as these securities do not have a single maturity date.