Investments in debt and equity securities. The total fair values of the Company's investments in debt and equity securities as of December 31 are detailed below:



	2018	2017
	($000 omitted)
Investments in:
Debt securities	602,020	671,441
Equity securities	33,997	37,914
	636,017	709,355

As of December 31, 2018 and 2017, included in the above fair values of investments in equity securities were net unrealized investment gains of $2.9 million and $5.8 million, respectively.

The amortized costs and fair values of investments in debt securities as of December 31, are as follows:



	2018		2017
	Amortized costs	Fair values	Amortized costs	Fair values
	($000 omitted)
Municipal	61,779	61,934	71,581	72,669
Corporate	333,289	328,495	351,477	357,933
Foreign	200,667	198,938	229,750	228,237
U.S. Treasury Bonds	12,951	12,653	12,838	12,602
	608,686	602,020	665,646	671,441

The Company believes its investment portfolio is diversified and expects no material loss to result from the failure to perform by issuers of the debt securities it holds. Investments made by the Company are not collateralized. Foreign debt securities primarily include Canadian government and corporate bonds, with aggregate fair values of $171.2 million and $198.7 million as of December 31, 2018 and 2017, respectively, and United Kingdom treasury and corporate bonds with aggregate fair values of $23.0 million and $24.5 million as of December 31, 2018 and 2017, respectively.

Gross unrealized gains and losses on investments in debt securities at December 31, were:



	2018		2017
	Gains	Losses	Gains	Losses
	($000 omitted)
Municipal	482	327	1,263	175
Corporate	1,894	6,688	6,953	497
Foreign	1,402	3,131	1,742	3,255
U.S. Treasury Bonds	2	300	—	236
	3,780	10,446	9,958	4,163

Debt securities at December 31, 2018 mature, according to their contractual terms, as follows (actual maturities may differ due to call or prepayment rights):



	Amortized costs	Fair values
	($000 omitted)
In one year or less	46,280	46,271
After one year through five years	345,026	341,976
After five years through ten years	184,655	181,621
After ten years	32,725	32,152
	608,686	602,020

Gross unrealized losses on investments in debt securities and the fair values of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2018, were:



	Less than 12 months		More than 12 months		Total
	Losses	Fair values	Losses	Fair values	Losses	Fair values
	($000 omitted)
Municipal	91	13,366	236	11,645	327	25,011
Corporate	4,416	201,965	2,272	71,044	6,688	273,009
Foreign	158	11,424	2,973	137,793	3,131	149,217
U.S. Treasury Bonds	—	—	300	12,544	300	12,544
	4,665	226,755	5,781	233,026	10,446	459,781

The number of specific debt securities investment holdings in an unrealized loss position as of December 31, 2018 was 307. Of these securities, 145 were in unrealized loss positions for more than 12 months. The increased gross unrealized losses on corporate debt securities were primarily driven by increases in the overall interest rate environment. Since the Company does not intend to sell and will more-likely-than-not maintain each investment until its maturity or anticipated recovery, and no significant credit risk is deemed to exist, these investments are not considered as other-than-temporarily-impaired. The Company believes its investment portfolio is diversified and expects no material loss to result from the failure to perform by issuers of the debt securities it holds. Investments made by the Company are not collateralized.



	Less than 12 months		More than 12 months		Total
	Losses	Fair values	Losses	Fair values	Losses	Fair values
	($000 omitted)
Municipal	58	17,023	117	5,784	175	22,807
Corporate	386	81,632	111	4,926	497	86,558
Foreign	1,528	116,130	1,727	39,031	3,255	155,161
U.S. Treasury Bonds	53	5,830	183	6,772	236	12,602
	2,025	220,615	2,138	56,513	4,163	277,128