Investments in debt and equity securities - Gross Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Gains	$ 21,843	$ 32,165
Losses	1,642	191
Municipal
Debt Securities, Available-for-sale [Line Items]
Gains	2,077	2,465
Losses	3	0
Corporate
Debt Securities, Available-for-sale [Line Items]
Gains	13,124	19,594
Losses	835	106
Foreign
Debt Securities, Available-for-sale [Line Items]
Gains	6,572	10,024
Losses	779	61
U.S. Treasury Bonds
Debt Securities, Available-for-sale [Line Items]
Gains	70	82
Losses	$ 25	$ 24

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

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- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

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