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Securities | 6 Months Ended
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Jun. 30, 2018
Marketable Securities [Abstract] |
Securities [Text Block] | Securities Trading Securities The fair value and net unrealized gain (loss) included in trading securities are as follows (in thousands):
|  | June 30, 2018 |  | December 31, 2017 |  | June 30, 2017
|  | Fair Value |  | Net Unrealized Gain (Loss) |  | Fair Value |  | Net Unrealized Gain (Loss) |  | Fair Value |  | Net Unrealized Gain (Loss)
U.S. government agency debentures |  | $ | 28,750 |  |  | $ | 10 |  |  | $ | 21,196 |  |  | $ | 8 |  |  | $ | 20,954 |  |  | $ | (9 | )
U.S. government agency residential mortgage-backed securities |  | 1,605,001 |  |  | 1,923 |  |  | 392,673 |  |  | (517 | ) |  | 365,171 |  |  | (1,032 | )
Municipal and other tax-exempt securities |  | 70,606 |  |  | 231 |  |  | 13,559 |  |  | 83 |  |  | 45,444 |  |  | 230 |
Asset-backed securities |  | 193,271 |  |  | 250 |  |  | 23,885 |  |  | (26 | ) |  | — |  |  | — |
Other trading securities |  | 11,987 |  |  | 32 |  |  | 11,363 |  |  | 4 |  |  | 9,845 |  |  | (175 | )
Total trading securities |  | $ | 1,909,615 |  |  | $ | 2,446 |  |  | $ | 462,676 |  |  | $ | (448 | ) |  | $ | 441,414 |  |  | $ | (986 | )
Investment Securities The amortized cost and fair values of investment securities are as follows (in thousands):
|  | June 30, 2018
|  | Amortized |  | Fair |  | Gross Unrealized
|  | Cost |  | Value |  | Gain |  | Loss
Municipal and other tax-exempt |  | $ | 173,097 |  |  | $ | 174,205 |  |  | $ | 1,779 |  |  | $ | (671 | )
U.S. government agency residential mortgage-backed securities |  | 13,989 |  |  | 13,984 |  |  | 232 |  |  | (237 | )
Other debt securities |  | 204,927 |  |  | 215,195 |  |  | 12,259 |  |  | (1,991 | )
Total investment securities |  | $ | 392,013 |  |  | $ | 403,384 |  |  | $ | 14,270 |  |  | $ | (2,899 | )
|  | December 31, 2017
|  | Amortized |  | Fair |  | Gross Unrealized
|  | Cost |  | Value |  | Gain |  | Loss
Municipal and other tax-exempt |  | $ | 228,186 |  |  | $ | 230,349 |  |  | $ | 2,967 |  |  | $ | (804 | )
U.S. government agency residential mortgage-backed securities |  | 15,891 |  |  | 16,242 |  |  | 446 |  |  | (95 | )
Other debt securities |  | 217,716 |  |  | 233,444 |  |  | 17,095 |  |  | (1,367 | )
Total investment securities |  | $ | 461,793 |  |  | $ | 480,035 |  |  | $ | 20,508 |  |  | $ | (2,266 | )
|  | June 30, 2017
|  | Amortized |  | Fair |  | Gross Unrealized
|  | Cost |  | Value |  | Gain |  | Loss
Municipal and other tax-exempt |  | $ | 267,375 |  |  | $ | 270,531 |  |  | $ | 3,384 |  |  | $ | (228 | )
U.S. government agency residential mortgage-backed securities |  | 18,035 |  |  | 18,642 |  |  | 668 |  |  | (61 | )
Other debt securities |  | 205,016 |  |  | 226,502 |  |  | 22,040 |  |  | (554 | )
Total investment securities |  | $ | 490,426 |  |  | $ | 515,675 |  |  | $ | 26,092 |  |  | $ | (843 | )
The amortized cost and fair values of investment securities at June 30, 2018, by contractual maturity, are as shown in the following table (dollars in thousands):
|  | Less than One Year |  | One to Five Years |  | Six to Ten Years |  | Over Ten Years |  | Total |  | Weighted Average Maturity²
Municipal and other tax-exempt: |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  | $ | 60,535 |  |  | $ | 62,005 |  |  | $ | 28,117 |  |  | $ | 22,440 |  |  | $ | 173,097 |  |  | 4.02 |
Fair value |  | 60,487 |  |  | 61,736 |  |  | 29,038 |  |  | 22,944 |  |  | 174,205 |  |  |
Nominal yield¹ |  | 2.07 | % |  | 2.58 | % |  | 5.81 | % |  | 5.12 | % |  | 3.25 | % |  |
Other debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  | 14,877 |  |  | 52,170 |  |  | 123,762 |  |  | 14,118 |  |  | 204,927 |  |  | 5.99 |
Fair value |  | 15,023 |  |  | 54,233 |  |  | 132,912 |  |  | 13,027 |  |  | 215,195 |  |  |
Nominal yield |  | 3.99 | % |  | 4.69 | % |  | 5.67 | % |  | 4.34 | % |  | 5.21 | % |  |
Total fixed maturity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  | $ | 75,412 |  |  | $ | 114,175 |  |  | $ | 151,879 |  |  | $ | 36,558 |  |  | $ | 378,024 |  |  | 5.08 |
Fair value |  | 75,510 |  |  | 115,969 |  |  | 161,950 |  |  | 35,971 |  |  | 389,400 |  |  |  |
Nominal yield |  | 2.45 | % |  | 3.54 | % |  | 5.69 | % |  | 4.82 | % |  | 4.31 | % |  |  |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  |  |  |  |  |  | $ | 13,989 |  |  | ³ |
Fair value |  |  |  |  |  |  |  |  |  |  |  |  |  | 13,984 |  |  |  |
Nominal yield4 |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.76 | % |  |  |
Total investment securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  |  |  |  |  |  | $ | 392,013 |  |  |  |
Fair value |  |  |  |  |  |  |  |  |  |  |  |  |  | 403,384 |  |  |  |
Nominal yield |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.26 | % |  |  |
1 | Calculated on a taxable equivalent basis using a 25 percent effective tax rate.
2 | Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty.
3 | The average expected lives of residential mortgage-backed securities were 5.0 years based upon current prepayment assumptions.
4 | The nominal yield on residential mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary - Unaudited for current yields on the investment securities portfolio.
Available for Sale Securities The amortized cost and fair value of available for sale securities are as follows (in thousands):
|  | June 30, 2018
|  | Amortized |  | Fair |  | Gross Unrealized |  |
|  | Cost |  | Value |  | Gain |  | Loss |  | OTTI
U.S. Treasury |  | $ | 494 |  |  | $ | 490 |  |  | $ | — |  |  | $ | (4 | ) |  | $ | — |
Municipal and other tax-exempt |  | 10,590 |  |  | 10,697 |  |  | 111 |  |  | (4 | ) |  | — |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U. S. government agencies: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNMA |  | 3,088,585 |  |  | 3,007,885 |  |  | 2,774 |  |  | (83,474 | ) |  | — |
FHLMC |  | 1,580,185 |  |  | 1,538,582 |  |  | 738 |  |  | (42,341 | ) |  | — |
GNMA |  | 772,785 |  |  | 758,093 |  |  | 915 |  |  | (15,607 | ) |  | — |
Total U.S. government agencies |  | 5,441,555 |  |  | 5,304,560 |  |  | 4,427 |  |  | (141,422 | ) |  | — |
Private issue |  | 65,376 |  |  | 83,224 |  |  | 18,221 |  |  | — |  |  | (373 | )
Total residential mortgage-backed securities |  | 5,506,931 |  |  | 5,387,784 |  |  | 22,648 |  |  | (141,422 | ) |  | (373 | )
Commercial mortgage-backed securities guaranteed by U.S. government agencies |  | 2,799,953 |  |  | 2,738,451 |  |  | 1,815 |  |  | (63,317 | ) |  | — |
Other debt securities |  | 25,500 |  |  | 25,444 |  |  | 12 |  |  | (68 | ) |  | — |
Total available for sale securities |  | $ | 8,343,468 |  |  | $ | 8,162,866 |  |  | $ | 24,586 |  |  | $ | (204,815 | ) |  | $ | (373 | )
|  | December 31, 2017
|  | Amortized |  | Fair |  | Gross Unrealized |  |
|  | Cost |  | Value |  | Gain |  | Loss |  | OTTI
U.S. Treasury |  | $ | 1,000 |  |  | $ | 1,000 |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Municipal and other tax-exempt |  | 27,182 |  |  | 27,080 |  |  | 181 |  |  | (283 | ) |  | — |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |
U. S. government agencies: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNMA |  | 3,021,551 |  |  | 2,997,563 |  |  | 11,549 |  |  | (35,537 | ) |  | — |
FHLMC |  | 1,545,971 |  |  | 1,531,009 |  |  | 3,148 |  |  | (18,110 | ) |  | — |
GNMA |  | 787,626 |  |  | 780,580 |  |  | 1,607 |  |  | (8,653 | ) |  | — |
Total U.S. government agencies |  | 5,355,148 |  |  | 5,309,152 |  |  | 16,304 |  |  | (62,300 | ) |  | — |
Private issue |  | 74,311 |  |  | 93,221 |  |  | 19,301 |  |  | — |  |  | (391 | )
Total residential mortgage-backed securities |  | 5,429,459 |  |  | 5,402,373 |  |  | 35,605 |  |  | (62,300 | ) |  | (391 | )
Commercial mortgage-backed securities guaranteed by U.S. government agencies |  | 2,858,885 |  |  | 2,834,961 |  |  | 1,963 |  |  | (25,887 | ) |  | — |
Other debt securities |  | 25,500 |  |  | 25,481 |  |  | 50 |  |  | (69 | ) |  | — |
Perpetual preferred stock |  | 12,562 |  |  | 15,767 |  |  | 3,205 |  |  | — |  |  | — |
Equity securities and mutual funds |  | 14,487 |  |  | 14,916 |  |  | 515 |  |  | (86 | ) |  | — |
Total available for sale securities |  | $ | 8,369,075 |  |  | $ | 8,321,578 |  |  | $ | 41,519 |  |  | $ | (88,625 | ) |  | $ | (391 | )
|  | June 30, 2017
|  | Amortized |  | Fair |  | Gross Unrealized |  |
|  | Cost |  | Value |  | Gain |  | Loss |  | OTTI
U.S. Treasury |  | $ | 1,000 |  |  | $ | 998 |  |  | $ | — |  |  | $ | (2 | ) |  | $ | — |
Municipal and other tax-exempt |  | 32,885 |  |  | 32,765 |  |  | 293 |  |  | (413 | ) |  | — |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |
U. S. government agencies: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNMA |  | 3,005,920 |  |  | 3,008,531 |  |  | 24,213 |  |  | (21,602 | ) |  | — |
FHLMC |  | 1,412,376 |  |  | 1,412,472 |  |  | 7,785 |  |  | (7,689 | ) |  | — |
GNMA |  | 938,086 |  |  | 936,365 |  |  | 3,641 |  |  | (5,362 | ) |  | — |
Other |  | 25,000 |  |  | 25,009 |  |  | 52 |  |  | (43 | ) |  | — |
Total U.S. government agencies |  | 5,381,382 |  |  | 5,382,377 |  |  | 35,691 |  |  | (34,696 | ) |  | — |
Private issue |  | 86,656 |  |  | 103,383 |  |  | 16,727 |  |  | — |  |  | — |
Total residential mortgage-backed securities |  | 5,468,038 |  |  | 5,485,760 |  |  | 52,418 |  |  | (34,696 | ) |  | — |
Commercial mortgage-backed securities guaranteed by U.S. government agencies |  | 2,788,543 |  |  | 2,782,070 |  |  | 7,804 |  |  | (14,277 | ) |  | — |
Other debt securities |  | 4,400 |  |  | 4,152 |  |  | — |  |  | (248 | ) |  | — |
Perpetual preferred stock |  | 12,562 |  |  | 16,568 |  |  | 4,006 |  |  | — |  |  | — |
Equity securities and mutual funds |  | 17,572 |  |  | 18,728 |  |  | 1,219 |  |  | (63 | ) |  | — |
Total available for sale securities |  | $ | 8,325,000 |  |  | $ | 8,341,041 |  |  | $ | 65,740 |  |  | $ | (49,699 | ) |  | $ | — |
The amortized cost and fair values of available for sale securities at June 30, 2018, by contractual maturity, are as shown in the following table (dollars in thousands):
| Less than One Year |  | One to Five Years |  | Six to Ten Years |  | Over Ten Years |  | Total |  | Weighted Average Maturity4
U.S. Treasuries: |  |  |  |  |  |  |  |  |  |  |
Amortized cost | $ | — |  |  | $ | 494 |  |  | $ | — |  |  | $ | — |  |  | $ | 494 |  |  | 1.59 |
Fair value | — |  |  | 490 |  |  | — |  |  | — |  |  | 490 |  |  |
Nominal yield | — | % |  | 1.99 | % |  | — | % |  | — | % |  | 1.99 | % |  |
Municipal and other tax-exempt: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost | $ | 4,574 |  |  | $ | 2,303 |  |  | $ | — |  |  | $ | 3,713 |  |  | $ | 10,590 |  |  | 6.53 |
Fair value | 4,580 |  |  | 2,401 |  |  | — |  |  | 3,716 |  |  | 10,697 |  |  |
Nominal yield¹ | 3.45 | % |  | 6.27 | % |  | — | % |  | 3.98 | % | 5 | 4.25 | % |  |
Commercial mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |
Amortized cost | $ | 8,070 |  |  | $ | 987,244 |  |  | $ | 1,548,520 |  |  | $ | 256,119 |  |  | $ | 2,799,953 |  |  | 6.89 |
Fair value | 8,041 |  |  | 968,540 |  |  | 1,512,106 |  |  | 249,764 |  |  | 2,738,451 |  |  |
Nominal yield | 1.67 | % |  | 1.96 | % |  | 2.17 | % |  | 2.20 | % |  | 2.10 | % |  |
Other debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 25,500 |  |  | $ | 25,500 |  |  | 14.18 |
Fair value | — |  |  | — |  |  | — |  |  | 25,444 |  |  | 25,444 |  |  |
Nominal yield | — | % |  | — | % |  | — | % |  | 1.59 | % | 5 | 1.59 | % |  |
Total fixed maturity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost | $ | 12,644 |  |  | $ | 990,041 |  |  | $ | 1,548,520 |  |  | $ | 285,332 |  |  | $ | 2,836,537 |  |  | 6.95 |
Fair value | 12,621 |  |  | 971,431 |  |  | 1,512,106 |  |  | 278,924 |  |  | 2,775,082 |  |  |
Nominal yield | 2.31 | % |  | 1.97 | % |  | 2.17 | % |  | 2.17 | % |  | 2.10 | % |  |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  |  |  |  |  | $ | 5,506,931 |  |  | 2 |
Fair value |  |  |  |  |  |  |  |  |  |  |  |  | 5,387,784 |  |  |
Nominal yield3 |  |  |  |  |  |  |  |  |  |  |  |  | 2.16 | % |  |
Total available-for-sale securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  |  |  |  |  | $ | 8,343,468 |  |  |  |
Fair value |  |  |  |  |  |  |  |  |  |  |  |  | 8,162,866 |  |  |  |
Nominal yield |  |  |  |  |  |  |  |  |  |  |  |  | 2.14 | % |  |  |
1 | Calculated on a taxable equivalent basis using a 25 percent effective tax rate.
2 | The average expected lives of mortgage-backed securities were 4.3 years years based upon current prepayment assumptions.
3 | The nominal yield on mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary –– Unaudited following for current yields on available for sale securities portfolio.
4 | Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty.
5 | Nominal yield on municipal and other tax-exempt securities and other debt securities with contractual maturity dates over ten years are based on variable rates which generally are reset within 35.
Sales of available for sale securities resulted in gains and losses as follows (in thousands):
| Three Months Ended June 30, |  | Six Months Ended June 30,
| 2018 |  | 2017 |  | 2018 |  | 2017
Proceeds | $ | 142,743 |  |  | $ | 460,402 |  |  | $ | 187,533 |  |  | $ | 700,412 |
Gross realized gains | 257 |  |  | 2,763 |  |  | 450 |  |  | 4,855 |
Gross realized losses | (1,019 | ) |  | (2,383 | ) |  | (1,502 | ) |  | (2,426 | )
Related federal and state income tax expense (benefit) | (194 | ) |  | 148 |  |  | (268 | ) |  | 945 |
A summary of investment and available for sale securities that have been pledged as collateral for repurchase agreements, public trust funds on deposit and for other purposes, as required by law was as follows (in thousands):
| June 30, 2018 |  | Dec. 31, 2017 |  | June 30, 2017
Investment: |  |  |  |  |
Amortized cost | $ | 172,906 |  |  | $ | 226,852 |  |  | $ | 251,684 |
Fair value | 174,240 |  |  | 229,429 |  |  | 255,097 |
Available for sale: |  |  |  |  |
Amortized cost | 6,821,287 |  |  | 7,151,468 |  |  | 6,327,666 |
Fair value | 6,653,875 |  |  | 7,089,346 |  |  | 6,317,623 |
The secured parties do not have the right to sell or repledge these securities. At June 30, 2018, trading securities and receivables collateralized by securities with a fair value of $889 million were pledged as collateral at the Federal Home Loan Bank (FHLB) for the trading activities. No trading securities were pledged as collateral as of December 31, 2017 and no trading securities were pledged as collateral at June 30, 2017. Temporarily Impaired Securities as of June 30, 2018 (in thousands):
|  | Number of Securities |  | Less Than 12 Months |  | 12 Months or Longer |  | Total
|  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Investment: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and other tax-exempt |  | 84 |  |  | $ | 98,325 |  |  | $ | 484 |  |  | $ | 5,007 |  |  | $ | 187 |  |  | $ | 103,332 |  |  | $ | 671 |
U.S. government agency residential mortgage-backed securities |  | 3 |  |  | 6,979 |  |  | 110 |  |  | 2,809 |  |  | 127 |  |  | 9,788 |  |  | 237 |
Other debt securities |  | 80 |  |  | 36,131 |  |  | 1,795 |  |  | 3,324 |  |  | 196 |  |  | 39,455 |  |  | 1,991 |
Total investment securities |  | 167 |  |  | $ | 141,435 |  |  | $ | 2,389 |  |  | $ | 11,140 |  |  | $ | 510 |  |  | $ | 152,575 |  |  | $ | 2,899 |
|  | Number of Securities |  | Less Than 12 Months |  | 12 Months or Longer |  | Total
|  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Treasury |  | 1 |  |  | $ | 490 |  |  | $ | 4 |  |  | $ | — |  |  | $ | — |  |  | $ | 490 |  |  | $ | 4 |
Municipal and other tax-exempt |  | 10 |  |  | 4,784 |  |  | 3 |  |  | 495 |  |  | 1 |  |  | 5,279 |  |  | 4 |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U. S. government agencies: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNMA |  | 174 |  |  | 2,049,432 |  |  | 44,860 |  |  | 710,962 |  |  | 38,614 |  |  | 2,760,394 |  |  | 83,474 |
FHLMC |  | 93 |  |  | 1,116,337 |  |  | 26,663 |  |  | 339,515 |  |  | 15,678 |  |  | 1,455,852 |  |  | 42,341 |
GNMA |  | 33 |  |  | 275,104 |  |  | 5,611 |  |  | 220,740 |  |  | 9,996 |  |  | 495,844 |  |  | 15,607 |
Total U.S. government agencies |  | 300 |  |  | 3,440,873 |  |  | 77,134 |  |  | 1,271,217 |  |  | 64,288 |  |  | 4,712,090 |  |  | 141,422 |
Private issue1 |  | 8 |  |  | 5,409 |  |  | 373 |  |  | — |  |  | — |  |  | 5,409 |  |  | 373 |
Total residential mortgage-backed securities |  | 308 |  |  | 3,446,282 |  |  | 77,507 |  |  | 1,271,217 |  |  | 64,288 |  |  | 4,717,499 |  |  | 141,795 |
Commercial mortgage-backed securities guaranteed by U.S. government agencies |  | 211 |  |  | 1,675,839 |  |  | 42,732 |  |  | 554,819 |  |  | 20,585 |  |  | 2,230,658 |  |  | 63,317 |
Other debt securities |  | 2 |  |  | — |  |  | — |  |  | 20,434 |  |  | 68 |  |  | 20,434 |  |  | 68 |
Total available for sale securities |  | 532 |  |  | $ | 5,127,395 |  |  | $ | 120,246 |  |  | $ | 1,846,965 |  |  | $ | 84,942 |  |  | $ | 6,974,360 |  |  | $ | 205,188 |
1 | Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income.
Temporarily Impaired Securities as of December 31, 2017 (In thousands)
|  | Number of Securities |  | Less Than 12 Months |  | 12 Months or Longer |  | Total
|  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Investment: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and other tax-exempt |  | 100 |  |  | $ | 145,960 |  |  | $ | 643 |  |  | $ | 5,833 |  |  | $ | 161 |  |  | $ | 151,793 |  |  | $ | 804 |
U.S. government agency residential mortgage-backed securities |  | 1 |  |  | — |  |  | — |  |  | 3,356 |  |  | 95 |  |  | 3,356 |  |  | 95 |
Other debt securities |  | 49 |  |  | 20,091 |  |  | 1,238 |  |  | 3,076 |  |  | 129 |  |  | 23,167 |  |  | 1,367 |
Total investment securities |  | 150 |  |  | $ | 166,051 |  |  | $ | 1,881 |  |  | $ | 12,265 |  |  | $ | 385 |  |  | $ | 178,316 |  |  | $ | 2,266 |
|  | Number of Securities |  | Less Than 12 Months |  | 12 Months or Longer |  | Total
|  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Treasury |  | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Municipal and other tax-exempt |  | 19 |  |  | 12,765 |  |  | 18 |  |  | 4,802 |  |  | 265 |  |  | 17,567 |  |  | 283 |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U. S. government agencies: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNMA |  | 113 |  |  | 1,203,041 |  |  | 9,618 |  |  | 824,029 |  |  | 25,919 |  |  | 2,027,070 |  |  | 35,537 |
FHLMC |  | 69 |  |  | 863,778 |  |  | 7,297 |  |  | 385,816 |  |  | 10,813 |  |  | 1,249,594 |  |  | 18,110 |
GNMA |  | 27 |  |  | 201,887 |  |  | 1,452 |  |  | 248,742 |  |  | 7,201 |  |  | 450,629 |  |  | 8,653 |
Total U.S. government agencies |  | 209 |  |  | 2,268,706 |  |  | 18,367 |  |  | 1,458,587 |  |  | 43,933 |  |  | 3,727,293 |  |  | 62,300 |
Private issue1 |  | 8 |  |  | 5,898 |  |  | 391 |  |  | — |  |  | — |  |  | 5,898 |  |  | 391 |
Total residential mortgage-backed securities |  | 217 |  |  | 2,274,604 |  |  | 18,758 |  |  | 1,458,587 |  |  | 43,933 |  |  | 3,733,191 |  |  | 62,691 |
Commercial mortgage-backed securities guaranteed by U.S. government agencies |  | 185 |  |  | 1,465,703 |  |  | 11,824 |  |  | 652,296 |  |  | 14,063 |  |  | 2,117,999 |  |  | 25,887 |
Other debt securities |  | 2 |  |  | 19,959 |  |  | 41 |  |  | 472 |  |  | 28 |  |  | 20,431 |  |  | 69 |
Perpetual preferred stocks |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Equity securities and mutual funds |  | 111 |  |  | 911 |  |  | 7 |  |  | 2,203 |  |  | 79 |  |  | 3,114 |  |  | 86 |
Total available for sale securities |  | 534 |  |  | $ | 3,773,942 |  |  | $ | 30,648 |  |  | $ | 2,118,360 |  |  | $ | 58,368 |  |  | $ | 5,892,302 |  |  | $ | 89,016 |
1 | Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income.
Temporarily Impaired Securities as of June 30, 2017 (In thousands)
|  | Number of Securities |  | Less Than 12 Months |  | 12 Months or Longer |  | Total
|  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Investment: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and other tax-exempt |  | 82 |  |  | $ | 111,078 |  |  | $ | 149 |  |  | $ | 3,000 |  |  | $ | 79 |  |  | $ | 114,078 |  |  | $ | 228 |
U.S. government agency residential mortgage-backed securities |  | 1 |  |  | 3,810 |  |  | 61 |  |  | — |  |  | — |  |  | 3,810 |  |  | 61 |
Other debt securities |  | 22 |  |  | 8,384 |  |  | 554 |  |  | — |  |  | — |  |  | 8,384 |  |  | 554 |
Total investment securities |  | 105 |  |  | $ | 123,272 |  |  | $ | 764 |  |  | $ | 3,000 |  |  | $ | 79 |  |  | $ | 126,272 |  |  | $ | 843 |
|  | Number of Securities |  | Less Than 12 Months |  | 12 Months or Longer |  | Total
|  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Treasury |  | 1 |  |  | $ | 997 |  |  | $ | 2 |  |  | $ | — |  |  | $ | — |  |  | $ | 997 |  |  | $ | 2 |
Municipal and other tax-exempt |  | 13 |  |  | 1,957 |  |  | 1 |  |  | 4,655 |  |  | 412 |  |  | 6,612 |  |  | 413 |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U. S. government agencies: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FNMA |  | 75 |  |  | 1,381,687 |  |  | 20,288 |  |  | 87,371 |  |  | 1,314 |  |  | 1,469,058 |  |  | 21,602 |
FHLMC |  | 42 |  |  | 731,853 |  |  | 7,213 |  |  | 16,388 |  |  | 476 |  |  | 748,241 |  |  | 7,689 |
GNMA |  | 21 |  |  | 291,806 |  |  | 3,766 |  |  | 76,605 |  |  | 1,596 |  |  | 368,411 |  |  | 5,362 |
Other |  | 1 |  |  | 19,957 |  |  | 43 |  |  | — |  |  | — |  |  | 19,957 |  |  | 43 |
Total U.S. government agencies |  | 139 |  |  | 2,425,303 |  |  | 31,310 |  |  | 180,364 |  |  | 3,386 |  |  | 2,605,667 |  |  | 34,696 |
Private issue1 |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Total residential mortgage-backed securities |  | 139 |  |  | 2,425,303 |  |  | 31,310 |  |  | 180,364 |  |  | 3,386 |  |  | 2,605,667 |  |  | 34,696 |
Commercial mortgage-backed securities guaranteed by U.S. government agencies |  | 121 |  |  | 1,388,406 |  |  | 12,690 |  |  | 78,828 |  |  | 1,587 |  |  | 1,467,234 |  |  | 14,277 |
Other debt securities |  | 2 |  |  | — |  |  | — |  |  | 4,152 |  |  | 248 |  |  | 4,152 |  |  | 248 |
Perpetual preferred stocks |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Equity securities and mutual funds |  | 91 |  |  | 1,668 |  |  | 22 |  |  | 887 |  |  | 41 |  |  | 2,555 |  |  | 63 |
Total available for sale securities |  | 367 |  |  | $ | 3,818,331 |  |  | $ | 44,025 |  |  | $ | 268,886 |  |  | $ | 5,674 |  |  | $ | 4,087,217 |  |  | $ | 49,699 |
1 | Includes securities for which an unrealized loss remains in AOCI after an other-than-temporary credit loss has been recognized in income.
Based on evaluations of impaired securities as of June 30, 2018, the Company does not intend to sell any impaired available for sale debt securities before fair value recovers to the current amortized cost and it is more-likely-than-not that the Company will not be required to sell impaired securities before fair value recovers, which may be maturity.
Fair Value Option Securities Fair value option securities represent securities which the Company has elected to carry at fair value and are separately identified on the Consolidated Balance Sheets. Changes in the fair value are recognized in earnings as they occur. Certain securities are held as an economic hedge of the mortgage servicing rights. The fair value and net unrealized gain (loss) included in fair value option securities is as follows (in thousands):
|  | June 30, 2018 |  | December 31, 2017 |  | June 30, 2017
|  | Fair Value |  | Net Unrealized Gain (Loss) |  | Fair Value |  | Net Unrealized Gain (Loss) |  | Fair Value |  | Net Unrealized Gain (Loss)
U.S. government agency residential mortgage-backed securities |  | $ | 482,227 |  |  | $ | (5,509 | ) |  | $ | 755,054 |  |  | $ | (1,877 | ) |  | $ | 445,169 |  |  | $ | 1,247 |
Restricted Equity Securities Restricted equity securities primarily include stock we are required to hold as members of the Federal Reserve system and the Federal Home Loan Banks. Restricted equity securities are carried at cost as these securities do not have a readily determined fair value because ownership of these shares are restricted and they lack a market. A summary of restricted equity securities follows (in thousands):
| June 30, 2018 |  | Dec. 31, 2017 |  | June 30, 2017
Federal Reserve stock | $ | 41,178 |  |  | $ | 40,746 |  |  | $ | 36,676 |
Federal Home Loan Bank stock | 306,543 |  |  | 279,200 |  |  | 274,113 |
Other | — |  |  | 243 |  |  | 244 |
Total | $ | 347,721 |  |  | $ | 320,189 |  |  | $ | 311,033 |

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