The difference between amortized cost or cost and estimated fair value and gross unrealized gains and losses, by major investment category, consisted of the following:


	Amortized		Gross		Gross
	Cost		Unrealized		Unrealized
	or Cost		Gains		Losses		Fair Value
	(In thousands)
December 31, 2020
Debt securities - available-for-sale:
United States government obligations and authorities	$	169,947	$	1,866	$	38	$	171,775
Obligations of states and political subdivisions	21,560		704		—		22,264
Corporate	254,618		11,989		79		266,528
International	27,001		659		17		27,643
	$	473,126	$	15,218	$	134	$	488,210


	Amortized		Gross		Gross
	Cost		Unrealized		Unrealized
	or Cost		Gains		Losses		Fair Value
	(In thousands)
December 31, 2019
Debt securities - available-for-sale:
United States government obligations and authorities	$	191,546	$	3,073	$	426	$	194,193
Obligations of states and political subdivisions	23,748		294		22		24,020
Corporate	268,182		10,252		132		278,302
International	29,169		593		12		29,750
	512,645		14,212		592		526,265

Debt securities - held-to-maturity:
United States government obligations and authorities	3,585		12		39		3,558
Corporate	697		20		—		717
International	55		1		—		56
	4,337		33		39		4,331
Total investments, excluding equity securities	$	516,982	$	14,245	$	631	$	530,596

The Company calculates the gain or loss realized on the sale of investments by comparing the sales price (fair value) to the cost or amortized cost of the security sold. Net realized gains and losses on investments are determined in accordance with the specific identification method.


	Year Ended December 31,
	2020		2019		2018
	(In thousands)
Gross realized and unrealized gains:
Debt securities	$	20,470	$	2,829	$	423
Equity securities	8,587		5,928		2,374
Total gross realized and unrealized gains	29,057		8,757		2,797

Gross realized and unrealized losses:
Debt securities	(2,879)		(664)		(3,990)
Equity securities	(8,146)		(1,009)		(2,951)
Total gross realized and unrealized losses	(11,025)		(1,673)		(6,941)
Net realized and unrealized gains (losses) on investments	$	18,032	$	7,084	$	(4,144)

The above line item, net realized and unrealized gains (losses) on investments, includes the following equity securities gains (losses) recognized in earnings:


	Year Ended December 31,
	2020		2019		2018
	(In thousands)
Net gains (losses) on equity securities:
Realized	$	4,555	$	803	$	591
Unrealized	(4,114)		4,116		(1,168)
	441		4,919		(577)
Less:
Net realized and unrealized gains (losses) on securities sold	309		672		732
Net unrealized gains (losses) still held as of the end-of-period	$	132	$	4,247	$	(1,309)


	December 31, 2020
	Amortized
	Cost		Fair Value
	(In thousands)
Securities with Maturity Dates
Debt securities, available-for-sale:
One year or less	$	21,454	$	21,573
Over one through five years	137,378		142,457
Over five through ten years	144,296		149,674
Over ten years	169,998		174,506
Total	$	473,126	$	488,210


	Year Ended December 31,
	2020		2019		2018
	(In thousands)
Interest income	$	11,563	$	15,605	$	12,253
Dividends income	223		296		207
Net investment income	$	11,786	$	15,901	$	12,460

Gross unrealized losses and related fair values for debt securities, grouped by duration of time in a continuous unrealized loss position, consisted of the following:


	Less than 12 months				12 months or longer				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
					(In thousands)
December 31, 2020
Debt securities - available-for-sale:
United States government obligations and authorities	$	25,521	$	38	$	—	$	—	$	25,521	$	38

Corporate	7,989		79		—		—		7,989		79
International	2,175		16		132		1		2,307		17
	$	35,685	$	133	$	132	$	1	$	35,817	$	134


	Less than 12 months				12 months or longer				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
					(In thousands)
December 31, 2019
Debt securities - available-for-sale:
United States government obligations and authorities	$	49,833	$	409	$	2,218	$	17	$	52,051	$	426
Obligations of states and political subdivisions	6,810		22		—		—		6,810		22
Corporate	15,872		94		7,694		38		23,566		132
International	3,856		10		179		2		4,035		12
	76,371		535		10,091		57		86,462		592

Debt securities, held-to-maturity:
United States government obligations and authorities	—		—		2,287		39		2,287		39



	—		—		2,287		39		2,287		39
Total investments, excluding equity securities	$	76,371	$	535	$	12,378	$	96	$	88,749	$	631

As of December 31, 2020, the Company held a total of 47 debt securities that were in an unrealized loss position, of which 2 securities were in an unrealized loss position continuously for 12 months or more. As of December 31, 2019, the Company held a total of 203 debt securities that were in an unrealized loss position, of which 24 securities were in an unrealized loss position continuously for 12 months or more. The unrealized losses associated with these securities consisted primarily of losses related to corporate securities. The Company did not have any OTTI losses on its available-for-sale securities for the years ended December 31, 2020, 2019 and 2018, respectively. Refer to Note 7 below for information regarding allowances for credit loss.

Cash and cash equivalents and investments, the majority of which were debt securities, with fair values of $11.5 million and $11.2 million were deposited with governmental authorities and into custodial bank accounts as required by law or contractual obligations, as of December 31, 2020 and 2019, respectively.