Transactions with Related Persons (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable, Related Parties [Roll Forward]
Beginning balance	$ 199	$ 74
New loans	5	134
Repayments	(59)	(9)
Ending balance	145	199
Unfunded loan commitments available to related parties	$ 2,600	$ 4,300
Price of repurchased shares (usd per share)	$ 451.33	$ 432.78
Class A Common Stock
Loans and Leases Receivable, Related Parties [Roll Forward]
Share repurchased from related party (in shares)	998,910	382,000
Class A Common Stock \| Related Party
Loans and Leases Receivable, Related Parties [Roll Forward]
Share repurchased from related party (in shares)	100,000
Price of repurchased shares (usd per share)	$ 464.90

Stock Repurchased During Period, Average Price Per Share

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- Definition

Unfunded Loan Commitments Available To Related Parties

+ References

No definition available.

+ Details

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- Definition

For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(e))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Period Type:	instant

- Definition

Reflects the amount of new advances made to related parties in the form of loan and lease receivables.

+ References

+ Details

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- Definition

Amount of cash inflow from related parties which reduce the amount of loans and leases receivable due from related parties.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(e)(1)(i))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

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-Name Accounting Standards Codification
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