Summary of Significant Accounting Policies - Schedule of Changes in the Balance of Each Component of Accumulated Other Comprehensive Earnings (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance			$ 108,714				$ 108,714
Accounting Standards Update [Extensible List]						ASU 2016-13
Net current-period other comprehensive earnings (loss)	$ (12,240)	$ 15,177	(44,747)	$ 9,550	$ 53,571	$ (13,031)	(41,810)	$ 50,090
Ending balance	66,904						66,904
Balance of securities for which an allowance for credit losses has been recognized in net earnings	426			795			426	795
Unrealized Gains and Losses on Available-for-Sale Securities
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	79,144		108,714	93,035		52,473	108,714	52,473
Other comprehensive earnings (loss) before reclassifications	(12,114)			10,412			(40,307)	52,264
Amounts reclassified from accumulated other comprehensive earnings	(126)			(862)			(1,503)	(2,174)
Ending balance	$ 66,904	79,144		$ 102,585	93,035		$ 66,904	102,585
Unrealized Gains and Losses on Available-for-Sale Securities | Cumulative Effect, Period of Adoption, Adjustment
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance						22		$ 22
Accounting Standards Update [Extensible List]	ASU 2016-13			ASU 2016-13			ASU 2016-13	ASU 2016-13
Unrealized Gains and Losses on Available-for-Sale Securities | Cumulative Effect, Period of Adoption, Adjusted Balance
Changes in the balance of each component of accumulated other comprehensive earnings
Beginning balance	$ 79,144		$ 108,714	$ 93,035		$ 52,495	$ 108,714	$ 52,495
Ending balance		$ 79,144			$ 93,035