Debt - Additional Information (Details)		6 Months Ended
	May 11, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Activity-based common stock ownership percentage		0.041
FHLB stock		$ 16,500,000	$ 14,300,000
Long-term debt, net, book value		1,798,117,000	1,793,452,000
Total short-term debt, par value		260,000,000
Federal Home Loan Bank Borrowings
Debt Instrument [Line Items]
Total short-term debt, par value		0	0
Estimate of Fair Value Measurement | Asset Pledged as Collateral
Debt Instrument [Line Items]
Fair value of pledged assets		$ 902,000,000
Junior Subordinated Debentures Due 2056
Debt Instrument [Line Items]
Interest rate		4.25%
Senior Notes Due 2023
Debt Instrument [Line Items]
Debt	$ 170,000,000	$ 0	165,500,000
Long-term debt, term	18 months
Proceeds from issuance of senior long-term debt	$ 166,000,000
Interest rate	7.875%	7.875%
Senior Notes
Debt Instrument [Line Items]
Optional redemption, period from issuance date		5 years
Federal Home Loan Bank Borrowings
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 655,000,000
Long-term debt, net, book value		$ 88,000,000	$ 23,000,000