The amortized cost and estimated fair values of our fixed maturities at June 30, 2021 were as follows:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(in thousands)
Held to Maturity
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	89,716	$	2,839	$	649	$	91,906
Obligations of states and political subdivisions		346,517		20,073		788		365,802
Corporate securities		188,162		15,061		267		202,956
Mortgage-backed securities		19,453		1,005		—		20,458

Totals	$	643,848	$	38,978	$	1,704	$	681,122


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(in thousands)
Available for Sale
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	22,508	$	257	$	439	$	22,326
Obligations of states and political subdivisions		59,378		2,366		31		61,713
Corporate securities		201,634		9,644		202		211,076
Mortgage-backed securities		222,814		5,068		417		227,465

Totals	$	506,334	$	17,335	$	1,089	$	522,580

At June 30, 2021, our holdings of obligations of states and political subdivisions included general obligation bonds with an aggregate fair value of $267.8 million and an amortized cost of $254.2 million. Our holdings at June 30, 2021 also included special revenue bonds with an aggregate fair value of $159.7 million and an amortized cost of $151.7 million. With respect to both categories of those bonds at June 30, 2021, we held no securities of any issuer that comprised more than 10% of our holdings of either bond category. Education bonds and water and sewer utility bonds represented 46% and 35%, respectively, of our total investments in special revenue bonds based on the carrying values of these investments at June 30, 2021. Many of the issuers of the special revenue bonds we held at June 30, 2021 have the authority to impose ad valorem taxes. In that respect, many of the special revenue bonds we held at June 30, 2021 are similar to general obligation bonds.

The amortized cost and estimated fair values of our fixed maturities at December 31, 2020 were as follows:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(in thousands)
Held to Maturity
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	77,435	$	3,984	$	223	$	81,196
Obligations of states and political subdivisions		312,319		23,212		143		335,388
Corporate securities		173,270		18,172		206		191,236
Mortgage-backed securities		23,585		1,236		—		24,821

Totals	$	586,609	$	46,604	$	572	$	632,641


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(in thousands)
Available for Sale
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	47,512	$	424	$	121	$	47,815
Obligations of states and political subdivisions		66,287		2,690		12		68,965
Corporate securities		202,396		10,496		184		212,708
Mortgage-backed securities		218,763		6,902		17		225,648

Totals	$	534,958	$	20,512	$	334	$	555,136

At December 31, 2020, our holdings of obligations of states and political subdivisions included general obligation bonds with an aggregate fair value of $263.6 million and an amortized cost of $247.5 million. Our holdings also included special revenue bonds with an aggregate fair value of $140.8 million and an amortized cost of $131.1 million. With respect to both categories of bonds, we held no securities of any issuer that comprised more than 10% of that category at December 31, 2020. Education bonds and water and sewer utility bonds represented 44% and 39%, respectively, of our total investments in special revenue bonds based on their carrying values at December 31, 2020. Many of the issuers of the special revenue bonds we held at December 31, 2020 have the authority to impose ad valorem taxes. In that respect, many of the special revenue bonds we held are similar to general obligation bonds.

We made reclassifications from available for sale to held to maturity of certain fixed maturities at fair value on November 30, 2013. We segregated within accumulated other comprehensive income the net unrealized losses of $15.1 million arising prior to the November 30, 2013 reclassifications. We are amortizing this balance over the remaining life of the related securities as an adjustment to yield in a manner consistent with the accretion of discount on the same fixed maturities. We recorded amortization of $556,553 and $833,690 in other comprehensive (loss) income during the six months ended June 30, 2021 and 2020, respectively. At June 30, 2021 and December 31, 2020, net unrealized losses of $5.5 million and $6.1 million, respectively, remained within accumulated other comprehensive income.

We show below the amortized cost and estimated fair value of our fixed maturities at June 30, 2021 by contractual maturity. Expected maturities may differ from contractual maturities because issuers of the securities may have the right to call or prepay obligations with or without call or prepayment penalties.


	Amortized Cost		Estimated Fair Value
	(in thousands)
Held to maturity
Due in one year or less	$	38,641	$	39,762
Due after one year through five years		83,282		88,929
Due after five years through ten years		224,135		237,348
Due after ten years		278,337		294,625
Mortgage-backed securities		19,453		20,458

Total held to maturity	$	643,848	$	681,122


Available for sale
Due in one year or less	$	26,146	$	26,621
Due after one year through five years		131,837		138,624
Due after five years through ten years		96,413		99,711
Due after ten years		29,124		30,159
Mortgage-backed securities		222,814		227,465

Total available for sale	$	506,334	$	522,580

The cost and estimated fair values of our equity securities at June 30, 2021 were as follows:


	Cost		Gross Gains		Gross Losses		Estimated Fair Value
	(in thousands)
Equity securities	$	50,864	$	22,007	$	114	$	72,757

The cost and estimated fair values of our equity securities at December 31, 2020 were as follows:


	Cost		Gross Gains		Gross Losses		Estimated Fair Value
	(in thousands)
Equity securities	$	42,410	$	17,103	$	957	$	58,556

Gross investment gains and losses before applicable income taxes for the three months and six months ended June 30, 2021 and 2020 were as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(in thousands)				(in thousands)
Gross investment gains:
Fixed maturities	$	479	$	229	$	524	$	652
Equity securities		3,762		6,474		6,728		3,355

		4,241		6,703		7,252		4,007

Gross investment losses:
Fixed maturities		—		217		74		218
Equity securities		—		—		468		7,998

		—		217		542		8,216

Net investment gains (losses)	$	4,241	$	6,486	$	6,710	$	(4,209	)

We recognized $6.1 million of gains and $114,339 of losses on equity securities we held at June 30, 2021 in net investment gains for the six months ended June 30, 2021. We recognized $3.4 million of gains and $4.9 million of losses on equity securities we held at June 30, 2020 in net investment losses for the six months ended June 30, 2020.

We held fixed maturities with unrealized losses representing declines that we considered temporary at June 30, 2021 as follows:


	Less Than 12 Months				More Than 12 Months
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(in thousands)
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	38,202	$	1,088	$	—	$	—
Obligations of states and political subdivisions		45,446		819		—		—
Corporate securities		38,846		344		3,375		125
Mortgage-backed securities		55,930		415		487		2

Totals	$	178,424	$	2,666	$	3,862	$	127

We held fixed maturities with unrealized losses representing declines that we considered temporary at December 31, 2020 as follows:


	Less Than 12 Months				More Than 12 Months
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(in thousands)
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	29,144	$	345	$	—	$	—
Obligations of states and political subdivisions		9,362		154		—		—
Corporate securities		26,143		115		8,230		276
Mortgage-backed securities		3,091		15		236		1

Totals	$	67,740	$	629	$	8,466	$	277

We make estimates concerning the valuation of our investments and the recognition of other-than-temporary declines in the value of our investments. For equity securities, we measure investments at fair value, and we recognize changes in fair value in

our results of operations. With respect to a debt security that is in an unrealized loss position, we first assess if we intend to sell the debt security. If we determine we intend to sell the debt security, we recognize the impairment loss in our results of operations. If we do not intend to sell the debt security, we determine whether it is more likely than not that we will be required to sell the debt security prior to recovery. If we determine it is more likely than not that we will be required to sell the debt security prior to recovery, we recognize the impairment loss in our results of operations. If we determine it is more likely than not that we will not be required to sell the debt security prior to recovery, we then evaluate whether a credit loss has occurred with respect to that security. We determine whether a credit loss has occurred by comparing the amortized cost of the debt security to the present value of the cash flows we expect to collect. If we expect a cash flow shortfall, we consider that a credit loss has occurred. If we determine that a credit loss has occurred, we consider the impairment to be other than temporary. We then recognize the amount of the impairment loss related to the credit loss in our results of operations, and we recognize the remaining portion of the impairment loss in our other comprehensive income, net of applicable taxes. In addition, we may write down securities in an unrealized loss position based on a number of other factors, including when the fair value of an investment is significantly below its cost, when the financial condition of the issuer of a security has deteriorated, the occurrence of industry, issuer or geographic events that have negatively impacted the value of a security and rating agency downgrades. We held 89

debt securities that were in an unrealized loss position at June 30, 2021. Based upon our analysis of general market conditions and underlying factors impacting these debt securities, we considered these declines in value to be temporary.

We amortize premiums and discounts on debt securities over the life of the security as an adjustment to yield using the effective interest method. We compute realized investment gains and losses using the specific identification method.

We amortize premiums and discounts on mortgage-backed debt securities using anticipated prepayments.