Investments - Additional Information (Details) $ in Thousands	Jun. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($)
Investment Holdings [Line Items]
Accrued investment income | $	$ 17,240	$ 16,126
ASU 2016-13
Investment Holdings [Line Items]
Change in accounting principle accounting standards update adopted	true
Change in accounting principle accounting standards update adoption date	Jan. 01, 2020
Debt Securities
Investment Holdings [Line Items]
Accrued investment income | $	$ 16,000	14,900
Number of debt securities for which there is an allowance for credit losses	13
Number of debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded	260
Unrealized loss | $	$ 7,772	$ 2,554
Unrealized losses as percentage of fixed income portfolio cost basis	0.40%
Unrealized losses relative to total invested assets (as a percent)	0.30%
Number of unrealized loss positions	260
Number of securities in unrealized loss positions for 12 months or longer	39