Securities - Fair value of securities available for sale and related unrealized gain and loss (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 1,490,347	$ 1,498,626
Unrealized Gains	4,696	3,989
Unrealized Losses	(154,262)	(172,134)
Fair Value	1,340,781	1,330,481
U.S. Government agencies
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	110,289	110,226
Unrealized Gains	45	24
Unrealized Losses	(10,185)	(11,777)
Fair Value	100,149	98,473
Mortgage Backed Securities - residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	700,397	711,131
Unrealized Gains	185	133
Unrealized Losses	(82,328)	(91,016)
Fair Value	618,254	620,248
Mortgage Backed Securities - commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	8,033	10,103
Unrealized Losses	(376)	(426)
Fair Value	7,657	9,677
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	226,009	228,344
Unrealized Gains	138	60
Unrealized Losses	(22,945)	(24,919)
Fair Value	203,202	203,485
State and municipal obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	403,085	396,522
Unrealized Gains	1,362	745
Unrealized Losses	(32,552)	(37,114)
Fair Value	371,895	360,153
Municipal taxable
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	39,882	39,321
Unrealized Gains	52	41
Unrealized Losses	(5,855)	(6,847)
Fair Value	34,079	32,515
U.S. Treasury
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	2,652	2,979
Unrealized Losses	(21)	(35)
Fair Value	2,631	2,944
Collateralized debt obligations
Amortized cost and fair value of investments classified as available for sale
Unrealized Gains	2,914	2,986
Fair Value	$ 2,914	$ 2,986