Securities - Fair value of securities available for sale and related unrealized gain and loss (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 1,386,111	$ 1,412,498
Unrealized Gains	3,656	4,484
Unrealized Losses	(171,480)	(157,845)
Fair Value	1,218,287	1,259,137
U.S. Government agencies
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	100,710	102,978
Unrealized Gains	3	4
Unrealized Losses	(12,599)	(11,542)
Fair Value	88,114	91,440
Mortgage Backed Securities - residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	638,535	653,507
Unrealized Gains	9	53
Unrealized Losses	(92,745)	(83,675)
Fair Value	545,799	569,885
Mortgage Backed Securities - commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	7,880	7,919
Unrealized Losses	(483)	(436)
Fair Value	7,397	7,483
Collateralized mortgage obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	204,572	209,398
Unrealized Gains		6
Unrealized Losses	(29,145)	(28,575)
Fair Value	175,427	180,829
State and municipal obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	393,628	397,413
Unrealized Gains	756	1,407
Unrealized Losses	(30,635)	(28,009)
Fair Value	363,749	370,811
Municipal taxable
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	39,869	39,872
Unrealized Gains		12
Unrealized Losses	(5,868)	(5,599)
Fair Value	34,001	34,285
U.S. Treasury
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	917	1,411
Unrealized Losses	(5)	(9)
Fair Value	912	1,402
Collateralized debt obligations
Amortized cost and fair value of investments classified as available for sale
Unrealized Gains	2,888	3,002
Fair Value	$ 2,888	$ 3,002