Derivatives and Hedging Activities - Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Cumulative basis adjustments for fair value hedges
Amortized cost of the Hedged Assets	$ 3,678,606		$ 3,807,239
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Fair Value		Fair Value
Amortized Cost of Fair Value Hedging Increase (Decrease) Included in the Carrying Amount of the Hedged Assets	$ 1,212		$ 17,988
Interest rate swap
Notional and estimated fair value amount of derivative positions
Notional Amount	1,500,000		1,500,000
Asset Derivative	1,067		0
Liability Derivative	$ 2,279		$ 17,988
Remaining Maturity	1 year 10 months 24 days		2 years 1 month 6 days
Interest rate swap | Interest income on investment securities
Fair value hedge relationships on the income statement
Gain (loss) on fair value hedges recognized in earnings	$ 3,078	$ 0
AFS debt securities | Interest income on investment securities
Fair value hedge relationships on the income statement
Gain (loss) on fair value hedges recognized in earnings	$ (3,078)	$ 0
SOFR | Interest rate swap
Notional and estimated fair value amount of derivative positions
Pay Rate	4.63%		4.63%