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Investments, Summary of Investments (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020
Summary of Investments [Abstract] |  |  |
Amortized cost |  | $ 1,278,684 | $ 1,533,544
Gross unrealized gains |  | 25,115 | 24,515
Gross unrealized losses |  | (5,148) | (2,821)
Estimated fair value |  | 1,298,651 | 1,555,238
Available-for-sale Securities [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 1,251,172 | 1,513,770
Gross unrealized gains |  | 1,263 | 8,577
Gross unrealized losses |  | (4,311) | (140)
Estimated fair value |  | 1,248,124 | 1,522,207
Available-for-sale Securities [Member] | Securities with Maturity of One Year or Less [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 612,557 | 1,025,454
Gross unrealized gains |  | 792 | 2,977
Gross unrealized losses |  | (345) | (71)
Estimated fair value |  | 613,004 | 1,028,360
Available-for-sale Securities [Member] | Securities with Maturity of More than One Year [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 638,615 | 488,316
Gross unrealized gains |  | 471 | 5,600
Gross unrealized losses |  | (3,966) | (69)
Estimated fair value |  | 635,120 | 493,847
Corporate Debt Securities [Member] | Securities with Maturity of One Year or Less [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost | [1] | 383,870 | 514,182
Gross unrealized gains |  | 728 | 2,194
Gross unrealized losses |  | (226) | (41)
Estimated fair value |  | 384,372 | 516,335
Corporate Debt Securities [Member] | Securities with Maturity of More than One Year [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 382,000 | 325,079
Gross unrealized gains |  | 331 | 4,941
Gross unrealized losses |  | (2,644) | (40)
Estimated fair value |  | 379,687 | 329,980
Debt Securities Issued by U.S. Government Agencies [Member] | Securities with Maturity of One Year or Less [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 48,493 | 94,234
Gross unrealized gains |  | 19 | 354
Gross unrealized losses |  | (18) | (2)
Estimated fair value |  | 48,494 | 94,586
Debt Securities Issued by U.S. Government Agencies [Member] | Securities with Maturity of More than One Year [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 72,935 | 80,099
Gross unrealized gains |  | 0 | 185
Gross unrealized losses |  | (561) | (9)
Estimated fair value |  | 72,374 | 80,275
Debt Securities Issued by the U.S. Treasury [Member] | Securities with Maturity of One Year or Less [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost | [1] | 45,424 | 307,576
Gross unrealized gains |  | 0 | 233
Gross unrealized losses |  | (64) | (9)
Estimated fair value |  | 45,360 | 307,800
Debt Securities Issued by the U.S. Treasury [Member] | Securities with Maturity of More than One Year [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 137,635 | 50,318
Gross unrealized gains |  | 139 | 383
Gross unrealized losses |  | (500) | (4)
Estimated fair value |  | 137,274 | 50,697
Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member] | Securities with Maturity of One Year or Less [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 134,770 | 104,271
Gross unrealized gains |  | 45 | 196
Gross unrealized losses |  | (37) | (12)
Estimated fair value |  | 134,778 | 104,455
Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member] | Securities with Maturity of More than One Year [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 39,909 | 31,779
Gross unrealized gains |  | 1 | 91
Gross unrealized losses |  | (224) | (16)
Estimated fair value |  | 39,686 | 31,854
Other Municipal Debt Securities [Member] | Securities with Maturity of One Year or Less [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  |  | 5,191
Gross unrealized gains |  |  | 0
Gross unrealized losses |  |  | (7)
Estimated fair value |  |  | 5,184
Other Municipal Debt Securities [Member] | Securities with Maturity of More than One Year [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 6,136 | 1,041
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | (37) | 0
Estimated fair value |  | 6,099 | 1,041
Equity Securities [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost |  | 27,512 | 19,774
Gross unrealized gains |  | 23,852 | 15,938
Gross unrealized losses |  | (837) | (2,681)
Estimated fair value |  | 50,527 | 33,031
Equity Securities in Publicly Traded Company [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost | [2] | 11,897 | 4,712
Gross unrealized gains |  | 7,145 | 0
Gross unrealized losses |  | (837) | (2,681)
Estimated fair value |  | 18,205 | 2,031
Equity Securities in Private Companies [Member] |  |  |
Summary of Investments [Abstract] |  |  |
Amortized cost | [3] | 15,615 | 15,062
Gross unrealized gains |  | 16,707 | 15,938
Gross unrealized losses |  | 0 | 0
Estimated fair value |  | $ 32,322 | $ 31,000
[1] | Includes investments classified as cash equivalents on our consolidated balance sheet.
[2] | Our equity securities included in other current assets consisted of our investments in publicly traded companies. We recognize publicly traded equity securities at fair value.
[3] | Our equity securities included in deposits and other assets consisted of our investments in privately held companies. We recognize our private company equity securities at cost minus impairments, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer on our consolidated balance sheet.

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