4. Investments

The amortized cost and estimated fair value of investments in debt and equity securities by category is as follows (in thousands):


			Gross		Gross
			Unrealized		Unrealized
	Amortized Cost		Gains		Losses		Fair Value
As of March 31, 2019
U.S. Treasury securities and obligations of U.S. Government	$	48,490	$	7	$	(288)	$	48,209
Corporate bonds		217,979		1,296		(440)		218,835
Collateralized corporate bank loans		130,526		66		(1,752)		128,840
Municipal bonds		113,812		845		(298)		114,359
Mortgage-backed		12,938		14		(218)		12,734
Total debt securities		523,745		2,228		(2,996)		522,977
Total equity securities		68,709		25,549		(5,602)		88,656
Total other investments		3,763		—		(2,579)		1,184
Total investments	$	596,217	$	27,777	$	(11,177)	$	612,817

As of December 31, 2018
U.S. Treasury securities and obligations of U.S. Government	$	48,609	$	5	$	(508)	$	48,106
Corporate bonds		243,314		440		(1,602)		242,152
Collateralized corporate bank loans		131,779		19		(5,270)		126,528
Municipal bonds		112,574		3,791		(838)		115,527
Mortgage-backed		13,992		11		(446)		13,557
Total debt securities		550,268		4,266		(8,664)		545,870
Total equity securities		68,709		20,693		(8,506)		80,896
Total other investments		3,763		—		(2,615)		1,148
Total investments	$	622,740	$	24,959	$	(19,785)	$	627,914

Major categories of net investment gains (losses) on investments are summarized as follows (in thousands):


	Three Months Ended March 31,
	2019		2018
U.S. Treasury securities and obligations of U.S. Government	$	—	$	—
Corporate bonds		23		(8)
Collateralized corporate bank loans		17		12
Municipal bonds		4,101		(21)
Mortgage-backed		—		2
Equity securities		—		—
Gain (loss) on investments		4,141		(15)
Unrealized gains (losses) on other investments		36		(363)
Unrealized gains (losses) on equity investments		7,760		(4,457)
Investment gains (losses), net	$	11,937	$	(4,835)

We realized gross gains on investments of $4.2 million and $60 thousand during the three months ended March 31, 2019 and 2018, respectively. We realized gross losses on investments of $0.1 million and $75 thousand for the three months ended March 31, 2019 and 2018, respectively. We had no proceeds from the sale of investment securities during the three months ended March 31, 2019 or 2018. Realized investment gains and losses are recognized in operations on the first in-first out method.

The following schedules summarize the gross unrealized losses showing the length of time that investments have been continuously in an unrealized loss position as of March 31, 2019 and December 31, 2018 (in thousands):


	As of March 31, 2019
	12 months or less				Longer than 12 months				Total
			Unrealized				Unrealized				Unrealized
	Fair Value		Losses		Fair Value		Losses		Fair Value		Losses
U.S. Treasury securities and obligations of U.S. Government	$	—	$	—	$	47,205	$	(288)	$	47,205	$	(288)
Corporate bonds		13,462		(72)		85,392		(368)		98,854		(440)
Collateralized corporate bank loans		115,083		(1,660)		4,832		(92)		119,915		(1,752)
Municipal bonds		11,463		(79)		25,229		(219)		36,692		(298)
Mortgage-backed		769		-		8,825		(218)		9,594		(218)
Total debt securities		140,777		(1,811)		171,483		(1,185)		312,260		(2,996)
Total equity securities		16,082		(1,518)		5,537		(4,084)		21,619		(5,602)
Total other investments		914		(1,873)		270		(706)		1,184		(2,579)
Total investments	$	157,773	$	(5,202)	$	177,290	$	(5,975)	$	335,063	$	(11,177)


	As of December 31, 2018
	12 months or less				Longer than 12 months				Total
			Unrealized				Unrealized				Unrealized
	Fair Value		Losses		Fair Value		Losses		Fair Value		Losses
U.S. Treasury securities and obligations of U.S. Government	$	18,902	$	(181)	$	28,201	$	(327)	$	47,103	$	(508)
Corporate bonds		117,450		(907)		100,060		(695)		217,510		(1,602)
Collateralized corporate bank loans		120,410		(4,938)		4,931		(332)		125,341		(5,270)
Municipal bonds		14,281		(96)		25,891		(742)		40,172		(838)
Mortgage-backed		6,592		(60)		5,986		(386)		12,578		(446)
Total debt securities		277,635		(6,182)		165,069		(2,482)		442,704		(8,664)
Total equity securities		30,981		(3,699)		4,475		(4,807)		35,456		(8,506)
Total other investments		1,148		(2,615)		—		—		1,148		(2,615)
Total investments	$	309,764	$	(12,496)	$	169,544	$	(7,289)	$	479,308	$	(19,785)

We had a total of 232 debt securities with an unrealized loss, of which 137 were in an unrealized loss position for less than one year and 95 were in an unrealized loss position for a period of one year or greater, as of March 31, 2019. We had a total of 328 debt securities with an unrealized loss, of which 221 were in an unrealized loss position for less than one year and 107 were in an unrealized loss position for a period of one year or greater, as of December 31, 2018. We consider these losses as a temporary decline in value as they are predominately on securities that we do not intend to sell and do not believe we will be required to sell prior to recovery of our amortized cost basis. We see no other indications that the decline in values of these securities is other-than-temporary.

We complete a detailed analysis each quarter to assess whether any decline in the fair value of any fixed maturity investment below cost is deemed other-than-temporary. All fixed maturity investments with an unrealized loss are reviewed. We recognize an impairment loss when an investment’s value declines below cost, adjusted for accretion, amortization and previous other-than-temporary impairments, and it is determined that the decline is other-than-temporary.

We assess whether we intend to sell, or it is more likely than not that we will be required to sell, a fixed maturity investment before recovery of its amortized cost basis less any current period credit losses. For fixed maturity investments that are considered other-than-temporarily impaired and that we do not intend to sell and will not be required to sell, we separate the amount of the impairment into the amount that is credit related (credit loss component) and the amount due to all other factors. The credit loss component is recognized in earnings and is the difference between the investment’s amortized cost basis and the present value of its expected future cash flows. The remaining difference between the investment’s fair value and the present value of future expected cash flows is recognized in other comprehensive income.

Details regarding the carrying value of the other investments portfolio as of March 31, 2019 and December 31, 2018 are as follows (in thousands):


	2019		2018
Investment Type
Equity warrant	$	1,184	$	1,148
Total other investments	$	1,184	$	1,148

We acquired this warrant in an active market. The warrant entitles us to buy the underlying common stock of a publicly traded company at a fixed price until the expiration date of January 19, 2021.

The amortized cost and estimated fair value of debt securities at March 31, 2019 by contractual maturity are as follows. Expected maturities may differ from contractual maturities because certain borrowers may have the right to call or prepay obligations with or without penalties.


	Amortized Cost		Fair Value
	(in thousands)
Due in one year or less	$	122,350	$	121,972
Due after one year through five years		264,476		265,022
Due after five years through ten years		92,907		91,964
Due after ten years		31,074		31,285
Mortgage-backed		12,938		12,734
	$	523,745	$	522,977