Securities - Narrative (Details)	1 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	May 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) contract
Debt Securities, Available-for-sale [Line Items]
Allowance for credit losses		$ 0			$ 0		$ 0
Securities		1,315,303,000			1,315,303,000		1,366,680,000
Unrealized loss		962,096,000			962,096,000		1,002,437,000
Debt securities available for sale, at fair value		1,027,676,000			1,027,676,000		1,057,621,000
Pre-tax loss		1,235,000		$ 0	10,760,000	$ 0
Equity securities with readily determinable fair value not held for trading		2,500,000			2,500,000		11,383,000
Equity securities, original costs		2,500,000			2,500,000
Unrealized gains		0		$ 2,600,000	0	$ 1,900,000
Foreign Corporate Debt Securities
Debt Securities, Available-for-sale [Line Items]
Debt securities available for sale, at fair value		0			0		0
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Allowance for credit losses		0			0		0
Unrealized loss		247,345,000			247,345,000		275,706,000
Debt securities available for sale, at fair value		251,368,000			251,368,000		280,700,000
Proceeds from sale of debt securities, available-for-sale	$ 800,000
Pre-tax loss	$ 1,200,000
Equity Securities
Debt Securities, Available-for-sale [Line Items]
Debt securities available for sale, at fair value			$ 11,200,000
Realized loss			200,000
Investment-Grade
Debt Securities, Available-for-sale [Line Items]
Debt securities available for sale, at fair value		179,900,000			179,900,000		206,300,000
Unrealized loss			$ 16,600,000		25,300,000
Pledged as Collateral
Debt Securities, Available-for-sale [Line Items]
Securities pledged as collateral		181,900,000			181,900,000		314,500,000
Foreign Corporate Debt Securities
Debt Securities, Available-for-sale [Line Items]
Securities		9,900,000			9,900,000		9,700,000
US Government
Debt Securities, Available-for-sale [Line Items]
Allowance for credit losses		0			0		0
Investment-Grade
Debt Securities, Available-for-sale [Line Items]
Allowance for credit losses		0			0		0
Securities		227,400,000			227,400,000		258,800,000
Unrealized loss		27,100,000			27,100,000		24,100,000
Non-Investment-Grade
Debt Securities, Available-for-sale [Line Items]
Securities		19,900,000			19,900,000		16,900,000
Unrealized loss		$ 7,100,000			7,100,000		2,100,000
Signature Bond
Debt Securities, Available-for-sale [Line Items]
Unrealized loss							$ 9,100,000
Number of instruments held-for-sale | contract							1
Equity securities, unrealized loss							$ 900,000
Realized loss					$ 9,500,000
Mutual funds
Debt Securities, Available-for-sale [Line Items]
Equity securities, original costs							$ 12,700,000