Investment Securities - Allowance for Credit Loss Rollforward (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jan. 01, 2020
Debt Securities, Available-for-sale [Line Items]
Securities, available-for-sale, allowance for credit loss, beginning balance	$ 869
Adjustment to initially apply ASU No. 2016-13 for CECL	485
Securities, available-for-sale, allowance for credit loss, ending balance	485
Corporate Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Securities, available-for-sale, allowance for credit loss, beginning balance	869	$ 0
Adjustment to initially apply ASU No. 2016-13 for CECL	485	869
Additions for securities for which no previous expected credit losses were recognized	(19)
Change in securities for which a previous expected credit loss was recognized	403	(569)
Securities, available-for-sale, allowance for credit loss, ending balance	$ 485	$ 869
Corporate Bonds [Member] \| Cumulative Effect, Period Of Adoption, Adjustment
Debt Securities, Available-for-sale [Line Items]
Adjustment to initially apply ASU No. 2016-13 for CECL			$ 300

Amount of allowance for credit loss 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://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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Amount of expense for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), for which no credit loss was previously recorded.

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- Definition

Amount of expense (reversal of expense) for allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), not intended to be sold and not more likely than not will be required to sell before recovery of amortized cost basis, with previously recorded allowance.

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