Summary of Significant Accounting Policies - Interest income (Details) - USD ($)	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies
Amortization (accretion) of the premium (discount)	$ 2,525,000	$ 5,276,000	$ 3,836,000

Amount of accretion (amortization) of purchase discount (premium) on nonoperating securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Name:	us-gaap_InvestmentIncomeNetAmortizationOfDiscountAndPremium
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration