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Marketable Securities (Tables) | 6 Months Ended
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Jun. 30, 2022
Marketable Securities |
Schedule of marketable debt securities, classified as available-for-sale | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Gross Unrealized
​ | ​ | Amortized | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Fair
​ |  | Cost |  | Gains |  | Losses |  | Value
​ | ​ | (In thousands)
June 30, 2022 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Marketable securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. government and municipal obligations | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Maturing in one year or less | ​ | $ | 152,518 | ​ | $ | — | ​ | $ | (1,494) | ​ | $ | 151,024
Maturing after one year through three years | ​ | ​ | 3,887 | ​ | ​ | — | ​ | ​ | (17) | ​ | ​ | 3,870
Total U.S. government and municipal obligations | ​ | $ | 156,405 | ​ | $ | — | ​ | $ | (1,511) | ​ | $ | 154,894
Corporate debt securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Maturing in one year or less | ​ | $ | 149,304 | ​ | $ | — | ​ | $ | (829) | ​ | $ | 148,475
Maturing after one year through three years | ​ | ​ | 25,720 | ​ | ​ | — | ​ | ​ | (673) | ​ | ​ | 25,047
Total corporate debt securities | ​ | $ | 175,024 | ​ | $ | — | ​ | $ | (1,502) | ​ | $ | 173,522
Total marketable securities | ​ | $ | 331,429 | ​ | $ | — | ​ | $ | (3,013) | ​ | $ | 328,416
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Gross Unrealized
​ | ​ | Amortized | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Fair
​ | ​ | Cost |  | Gains |  | Losses |  | Value
​ | ​ | (In thousands)
December 31, 2021 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Marketable securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. government and municipal obligations | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Maturing in one year or less | ​ | $ | 80,674 | ​ | $ | — | ​ | $ | (133) | ​ | $ | 80,541
Maturing after one year through three years | ​ | ​ | 51,319 | ​ | ​ | — | ​ | ​ | (184) | ​ | ​ | 51,135
Total U.S. government and municipal obligations | ​ | $ | 131,993 | ​ | $ | — | ​ | $ | (317) | ​ | $ | 131,676
Corporate debt securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Maturing in one year or less | ​ | $ | 170,034 | ​ | $ | — | ​ | $ | (28) | ​ | $ | 170,006
Maturing after one year through three years | ​ | ​ | 67,782 | ​ | ​ | — | ​ | ​ | (357) | ​ | ​ | 67,425
Total corporate debt securities | ​ | $ | 237,816 | ​ | $ | — | ​ | $ | (385) | ​ | $ | 237,431
Total marketable securities | ​ | $ | 369,809 | ​ | $ | — | ​ | $ | (702) | ​ | $ | 369,107

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