Investments

The following table provides cost or amortized cost, gross unrealized gains, gross unrealized losses and fair value for our fixed-maturity and equity securities:



(Dollars in millions)	Cost or amortized cost
			Gross unrealized				Fair value
At March 31, 2017			gains		losses		Fair value
Fixed maturity securities:
Corporate	$	5,570	$	262	$	17	$	5,815
States, municipalities and political subdivisions	3,879		110		37		3,952
Commercial mortgage-backed	282		6		1		287
Government-sponsored enterprises	219		—		3		216
United States government	16		—		—		16
Foreign government	10		—		—		10
Convertibles and bonds with warrants attached	5		—		—		5
Subtotal	9,981		378		58		10,301
Equity securities:
Common equities	3,051		2,411		9		5,453
Nonredeemable preferred equities	189		34		—		223
Subtotal	3,240		2,445		9		5,676
Total	$	13,221	$	2,823	$	67	$	15,977
At December 31, 2016
Fixed maturity securities:
Corporate	$	5,555	$	252	$	26	$	5,781
States, municipalities and political subdivisions	3,770		100		42		3,828
Commercial mortgage-backed	282		7		2		287
Government-sponsored enterprises	167		—		3		164
United States government	10		—		—		10
Foreign government	10		—		—		10
Convertibles and bonds with warrants attached	5		—		—		5
Subtotal	9,799		359		73		10,085
Equity securities:
Common equities	2,812		2,320		9		5,123
Nonredeemable preferred equities	183		28		—		211
Subtotal	2,995		2,348		9		5,334
Total	$	12,794	$	2,707	$	82	$	15,419

The net unrealized investment gains in our fixed-maturity portfolio at March 31, 2017, are primarily the result of the continued low interest rate environment that increased the fair value of our fixed-maturity portfolio. Our commercial mortgage-backed securities had an average rating of Aa1/AA at March 31, 2017, and December 31, 2016. The seven largest unrealized investment gains in our common stock portfolio are from JP Morgan Chase & Co. (NYSE:JPM), Honeywell International Incorporated (NYSE:HON), Apple Inc. (Nasdaq:AAPL), Hasbro Inc. (Nasdaq:HAS), Microsoft Corporation (Nasdaq: MSFT), Exxon Mobil Corporation (NYSE:XOM), and Johnson & Johnson (NYSE:JNJ), which had a combined gross unrealized gain of $760 million. At March 31, 2017, Apple Inc. was our largest single equity holding with a fair value of $201 million, which was 3.7 percent of our publicly traded common equities portfolio and 1.3 percent of the total investment portfolio.

The table below provides fair values and gross unrealized losses by investment category and by the duration of the securities’ continuous unrealized loss positions:



(Dollars in millions)	Less than 12 months				12 months or more				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
At March 31, 2017	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Fixed maturity securities:
Corporate	$	381	$	10	$	136	$	7	$	517	$	17
States, municipalities and political subdivisions	883		37		—		—		883		37
Commercial mortgage-backed securities	75		1		2		—		77		1
Government-sponsored enterprises	165		3		—		—		165		3
United States government	6		—		—		—		6		—
Subtotal	1,510		51		138		7		1,648		58
Equity securities:
Common equities	236		9		4		—		240		9
Subtotal	236		9		4		—		240		9
Total	$	1,746	$	60	$	142	$	7	$	1,888	$	67
At December 31, 2016
Fixed maturity securities:
Corporate	$	733	$	15	$	189	$	11	$	922	$	26
States, municipalities and political subdivisions	989		42		—		—		989		42
Commercial mortgage-backed	89		2		2		—		91		2
Government-sponsored enterprises	155		3		—		—		155		3
United States government	6		—		—		—		6		—
Subtotal	1,972		62		191		11		2,163		73
Equity securities:
Common equities	103		9		—		—		103		9
Nonredeemable preferred equities	4		—		—		—		4		—
Subtotal	107		9		—		—		107		9
Total	$	2,079	$	71	$	191	$	11	$	2,270	$	82

Contractual maturity dates for fixed-maturity investments were:



(Dollars in millions)	Amortized cost		Fair value		% of fair value
At March 31, 2017	Amortized cost		Fair value		% of fair value
Maturity dates:
Due in one year or less	$	655	$	669	6.5	%
Due after one year through five years	2,764		2,911		28.3
Due after five years through ten years	3,862		3,981		38.6
Due after ten years	2,700		2,740		26.6
Total	$	9,981	$	10,301	100.0	%

Actual maturities may differ from contractual maturities when there is a right to call or prepay obligations with or without call or prepayment penalties.

The following table provides investment income, realized investment gains and losses, the change in unrealized investment gains and losses:



(Dollars in millions)	Three months ended March 31,
	2017			2016
Investment income:
Interest	$	111		$	109
Dividends	39			37
Other	1			1
Total	151			147
Less investment expenses	2			2
Total	$	149		$	145

Realized investment gains and losses:
Fixed maturities:
Gross realized gains	$	10		$	3
Gross realized losses	—			(1		)
Other-than-temporary impairments	—			(2		)
Equity securities:
Gross realized gains	153			62
Gross realized losses	(4		)	(1		)
Other-than-temporary impairments	—			—
Other	1			—
Total	$	160		$	61

Change in unrealized investment gains and losses:
Fixed maturities	$	34		$	116
Equity securities	97			174
Income tax (provision) benefit	(46		)	(100		)
Total	$	85		$	190

During the three months ended March 31, 2017, there were no equity securities and no fixed-maturity securities other-than-temporarily impaired. During the three months ended March 31, 2016, there were no equity securities and two fixed-maturity securities other-than-temporarily impaired. There were no credit losses on fixed-maturity securities for which a portion of other-than-temporary impairment (OTTI) has been recognized in other comprehensive income for the three months ended March 31, 2017 and 2016.

At March 31, 2017, 22 fixed-maturity investments with a total unrealized loss of $7 million had been in an unrealized loss position for 12 months or more. Of that total, no fixed-maturity investment had a fair value below 70 percent of amortized cost. At March 31, 2017, one equity investment with a total unrealized loss of less than $1 million had been in an unrealized loss position for 12 months or more. There were no equity investments with a fair value below 70 percent of amortized cost. At December 31, 2016, 32 fixed-maturity investments with a total unrealized loss of $11 million had been in an unrealized loss position for 12 months or more. Of that total, no fixed-maturity investments had fair values below 70 percent of amortized cost. There were no equity security investments in an unrealized loss position for 12 months or more as of December 31, 2016.