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Investments (Tables) | 3 Months Ended
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Mar. 31, 2018
Investments [Abstract] |
Amortized cost, gross unrealized gains and losses and fair value of fixed income securities | The amortized cost, gross unrealized gains and losses, and fair value of investments in fixed income securities classified as available-for-sale at March 31, 2018 and December 31, 2017 are shown in tables 7.1a and 7.1b below.
| Table | 7.1a |  |  |  |  |  |  |  |
Details of fixed income investments by category - current year |  |  |  | March 31, 2018
(In thousands) |  | Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses (1) |  | Fair Value
U.S. Treasury securities and obligations of U.S. government corporations and agencies |  | $ | 191,018 |  |  | $ | 256 |  |  | $ | (2,212 | ) |  | $ | 189,062 |
| Obligations of U.S. states and political subdivisions |  | 2,093,901 |  |  | 27,926 |  |  | (19,130 | ) |  | 2,102,697 |
| Corporate debt securities |  | 2,087,977 |  |  | 1,921 |  |  | (33,819 | ) |  | 2,056,079 |
| Asset backed securities (“ABS”) |  | 9,451 |  |  | — |  |  | (29 | ) |  | 9,422 |
| Residential mortgage backed securities (“RMBS”) |  | 182,050 |  |  | 48 |  |  | (10,558 | ) |  | 171,540 |
| Commercial mortgage backed securities (“CMBS”) |  | 302,434 |  |  | 722 |  |  | (9,800 | ) |  | 293,356 |
| Collateralized loan obligations (“CLO”) |  | 107,785 |  |  | 163 |  |  | (41 | ) |  | 107,907 |
| Total fixed income securities |  | 4,974,616 |  |  | 31,036 |  |  | (75,589 | ) |  | 4,930,063 |
| Table | 7.1b |  |  |  |  |  |  |  |
Details of fixed income investments by category - prior year-end |  |  |  | December 31, 2017
(In thousands) |  | Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses (1) |  | Fair Value
U.S. Treasury securities and obligations of U.S. government corporations and agencies |  | $ | 179,850 |  |  | $ | 274 |  |  | $ | (1,278 | ) |  | $ | 178,846 |
| Obligations of U.S. states and political subdivisions |  | 2,105,063 |  |  | 56,210 |  |  | (8,749 | ) |  | 2,152,524 |
| Corporate debt securities |  | 2,065,475 |  |  | 10,532 |  |  | (9,169 | ) |  | 2,066,838 |
| ABS |  | 4,925 |  |  | — |  |  | (2 | ) |  | 4,923 |
| RMBS |  | 189,153 |  |  | 60 |  |  | (7,364 | ) |  | 181,849 |
| CMBS |  | 301,014 |  |  | 1,204 |  |  | (4,906 | ) |  | 297,312 |
| CLOs |  | 100,798 |  |  | 304 |  |  | (79 | ) |  | 101,023 |
| Total fixed income securities |  | 4,946,278 |  |  | 68,584 |  |  | (31,547 | ) |  | 4,983,315 |
(1) | At March 31, 2018 and December 31, 2017, there were no other-than-temporary impairment losses recorded in other comprehensive income.
Amortized cost and fair values of debt securities by contractual maturity | The amortized cost and fair values of fixed income securities at March 31, 2018, by contractual maturity, are shown in table 7.2 below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most ABS, RMBS, CMBS, and CLOs provide for periodic payments throughout their lives, they are listed in separate categories.
| Table | 7.2 |  |  |  |
Fixed income securities maturity schedule |  |  | March 31, 2018
(In thousands) |  | Amortized Cost |  | Fair Value
| Due in one year or less |  | $ | 650,415 |  |  | $ | 649,088 |
| Due after one year through five years |  | 1,507,245 |  |  | 1,487,678 |
| Due after five years through ten years |  | 909,711 |  |  | 893,329 |
| Due after ten years |  | 1,305,525 |  |  | 1,317,743 |
|  |  | $ | 4,372,896 |  |  | $ | 4,347,838 |
| ABS |  | 9,451 |  |  | 9,422 |
| RMBS |  | 182,050 |  |  | 171,540 |
| CMBS |  | 302,434 |  |  | 293,356 |
| CLOs |  | 107,785 |  |  | 107,907 |
| Total as of March 31, 2018 |  | $ | 4,974,616 |  |  | $ | 4,930,063 |
Cost and fair value of investments in equity securities | The cost and fair value of investments in equity securities at March 31, 2018 and December 31, 2017 are shown in tables 7.3a and 7.3b below. As described in Note 2 - “New Accounting Pronouncements,” updated guidance regarding the “Recognition and Measurement of Financial Assets and Financial Liabilities” became effective on January 1, 2018, which prohibits our investment in FHLB stock from being presented with equity securities. The amount of our FHLB stock investment has been reclassified and presented in “Other invested assets” on our consolidated balance sheet as of March 31, 2018.
| Table | 7.3a |  |  |  |  |  |  |  |
Details of equity security investments - current year |  |  |  | March 31, 2018
(In thousands) |  | Cost |  | Gross Gains |  | Gross Losses |  | Fair Value
Equity securities |  | $ | 4,143 |  |  | $ | 8 |  |  | $ | (52 | ) |  | $ | 4,099 |
| Table | 7.3b |  |  |  |  |  |  |  |
Details of equity security investments - prior year-end |  |  |  | December 31, 2017
(In thousands) |  | Cost |  | Gross Gains |  | Gross Losses |  | Fair Value
Equity securities |  | $ | 7,223 |  |  | $ | 39 |  |  | $ | (16 | ) |  | $ | 7,246 |
Aging of the fair values of securities in an unrealized loss position | Tables 7.4a and 7.4b below summarize, for all available-for-sale investments in an unrealized loss position at March 31, 2018 and December 31, 2017, the aggregate fair value and gross unrealized loss by the length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in tables 7.4a and 7.4b are estimated using the process described in Note 8 - “Fair Value Measurements” to these consolidated financial statements and in Note 3 - “Significant Accounting Policies” of the notes to the consolidated financial statements in our 2017 Annual Report on Form 10-K.
| Table | 7.4a |  |  |  |  |  |  |  |  |  |  |  |
Investments unrealized losses - current year |  |  |  | March 31, 2018
|  | Less Than 12 Months |  | 12 Months or Greater |  | Total
(In thousands) |  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
| U.S. Treasury securities and obligations of U.S. government corporations and agencies |  | $ | 77,510 |  |  | $ | (1,532 | ) |  | $ | 31,491 |  |  | $ | (680 | ) |  | $ | 109,001 |  |  | $ | (2,212 | )
| Obligations of U.S. states and political subdivisions |  | 905,755 |  |  | (11,622 | ) |  | 201,094 |  |  | (7,508 | ) |  | 1,106,849 |  |  | (19,130 | )
| Corporate debt securities |  | 1,743,627 |  |  | (26,797 | ) |  | 148,468 |  |  | (7,022 | ) |  | 1,892,095 |  |  | (33,819 | )
| ABS |  | 9,423 |  |  | (29 | ) |  | — |  |  | — |  |  | 9,423 |  |  | (29 | )
| RMBS |  | 14,226 |  |  | (416 | ) |  | 156,842 |  |  | (10,142 | ) |  | 171,068 |  |  | (10,558 | )
| CMBS |  | 114,206 |  |  | (2,162 | ) |  | 126,941 |  |  | (7,638 | ) |  | 241,147 |  |  | (9,800 | )
| CLOs |  | — |  |  | — |  |  | 1,936 |  |  | (41 | ) |  | 1,936 |  |  | (41 | )
| Total |  | $ | 2,864,747 |  |  | $ | (42,558 | ) |  | $ | 666,772 |  |  | $ | (33,031 | ) |  | $ | 3,531,519 |  |  | $ | (75,589 | )
| Table | 7.4b |  |  |  |  |  |  |  |  |  |  |  |
Investments unrealized losses - prior year-end |  |  |  | December 31, 2017
|  |  | Less Than 12 Months |  | 12 Months or Greater |  | Total
(In thousands) |  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
| U.S. Treasury securities and obligations of U.S. government corporations and agencies |  | $ | 144,042 |  |  | $ | (796 | ) |  | $ | 31,196 |  |  | $ | (482 | ) |  | $ | 175,238 |  |  | $ | (1,278 | )
| Obligations of U.S. states and political subdivisions |  | 505,311 |  |  | (3,624 | ) |  | 211,684 |  |  | (5,125 | ) |  | 716,995 |  |  | (8,749 | )
| Corporate debt securities |  | 932,350 |  |  | (4,288 | ) |  | 200,716 |  |  | (4,881 | ) |  | 1,133,066 |  |  | (9,169 | )
| ABS |  | 4,923 |  |  | (2 | ) |  | — |  |  | — |  |  | 4,923 |  |  | (2 | )
| RMBS |  | 14,979 |  |  | (280 | ) |  | 166,329 |  |  | (7,084 | ) |  | 181,308 |  |  | (7,364 | )
| CMBS |  | 51,096 |  |  | (358 | ) |  | 138,769 |  |  | (4,548 | ) |  | 189,865 |  |  | (4,906 | )
| CLOs |  | 14,243 |  |  | (7 | ) |  | 3,568 |  |  | (72 | ) |  | 17,811 |  |  | (79 | )
| Equity securities |  | 226 |  |  | (2 | ) |  | 431 |  |  | (14 | ) |  | 657 |  |  | (16 | )
| Total |  | $ | 1,667,170 |  |  | $ | (9,357 | ) |  | $ | 752,693 |  |  | $ | (22,206 | ) |  | $ | 2,419,863 |  |  | $ | (31,563 | )

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- Definition For all investments in an unrealized loss position, including those for which other-than-temporary impairments have not been recognized in earnings (including investments for which a portion of an other-than-temporary impairment has been recognized in other comprehensive income), a tabular disclosure of the aggregate related fair value of investments with unrealized losses and the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
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