Investments in debt and equity securities | Investments in debt and equity securities. The total fair values of the Company's investments in debt and equity securities are as follows: June 30, 2019 December 31, 2018 ($000 omitted) Investments in: Debt securities 579,823 602,020 Equity securities 37,526 33,997 617,349 636,017 As of June 30, 2019 and December 31, 2018 , the net unrealized investment gains relating to investments in equity securities held were $ 6.4 million and $ 2.9 million, respectively. The amortized costs and fair values of investments in debt securities are as follows: June 30, 2019 December 31, 2018 Amortized costs Fair values Amortized costs Fair values ($000 omitted) Municipal 60,141 61,578 61,779 61,934 Corporate 311,687 319,745 333,289 328,495 Foreign 189,650 192,068 200,667 198,938 U.S. Treasury Bonds 6,537 6,432 12,951 12,653 568,015 579,823 608,686 602,020 Foreign debt securities consist of Canadian government and corporate bonds, United Kingdom treasury and corporate bonds, and Mexican government bonds. Gross unrealized gains and losses on investments in debt securities are as follows: June 30, 2019 December 31, 2018 Gains Losses Gains Losses ($000 omitted) Municipal 1,439 2 482 327 Corporate 8,184 126 1,894 6,688 Foreign 3,022 604 1,402 3,131 U.S. Treasury Bonds 8 113 2 300 12,653 845 3,780 10,446 Debt securities as of June 30, 2019 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 50,679 50,634 After one year through five years 330,611 335,702 After five years through ten years 155,433 160,440 After ten years 31,292 33,047 568,015 579,823 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 June 30, 2019 , were: Less than 12 months More than 12 months Total Losses Fair values Losses Fair values Losses Fair values ($000 omitted) Municipal — — 2 506 2 506 Corporate 1 80 125 22,619 126 22,699 Foreign 30 21,616 574 59,053 604 80,669 U.S. Treasury Bonds — — 113 5,836 113 5,836 31 21,696 814 88,014 845 109,710 The number of specific debt investment holdings held in an unrealized loss position as of June 30, 2019 was 61 . Of these securities, 53 were in unrealized loss positions for more than 12 months. During 2019, the overall gross unrealized losses on debt securities improved compared to the prior year-end, primarily due to reduced interest rates and credit spreads which increased investment fair values. Since the Company does not intend to sell and will more likely than not maintain each investment security 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. 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 |