Investment Securities - Gross unrealized losses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Investment securities available-for-sale
Unrealized losses less than 12 months	$ (19,761)	$ (10,290)
Fair value less than 12 months	178,719	578,270
Unrealized losses over 12 months	(112,503)	(1,681)
Fair value over 12 months	535,024	55,084
Total Unrealized losses	(132,264)	(11,971)
Total Fair value	713,743	633,354
Held-to-maturity investment securities
Unrealized losses less than 12 months	(3,336)	(3,494)
Fair value less than 12 months	18,788	257,583
Unrealized losses over 12 months	(47,654)
Fair value over 12 months	249,623
Total Unrealized losses	(50,990)	(3,494)
Total Fair value	268,411	257,583
Unrealized losses less than 12 months	(23,097)	(13,784)
Fair value less than 12 months	197,507	835,853
Unrealized losses over 12 months	(160,157)	(1,681)
Fair value over 12 months	784,647	55,084
Total Unrealized losses	(183,254)	(15,465)
Total Fair value	982,154	890,937
U.S. treasury and government agencies
Investment securities available-for-sale
Unrealized losses less than 12 months	(17)
Fair value less than 12 months	509
Total Unrealized losses	(17)
Total Fair value	509
Mortgage backed securities - Residential agency
Investment securities available-for-sale
Unrealized losses less than 12 months	(10,457)	(10,156)
Fair value less than 12 months	79,693	554,811
Unrealized losses over 12 months	(107,711)	(1,681)
Fair value over 12 months	507,418	55,082
Total Unrealized losses	(118,168)	(11,837)
Total Fair value	587,111	609,893
Held-to-maturity investment securities
Unrealized losses less than 12 months		(3,145)
Fair value less than 12 months		204,373
Unrealized losses over 12 months	(33,254)
Fair value over 12 months	150,861
Total Unrealized losses	(33,254)	(3,145)
Total Fair value	150,861	204,373
Mortgage backed securities - Commercial
Investment securities available-for-sale
Unrealized losses less than 12 months	(4,835)	(123)
Fair value less than 12 months	50,437	17,470
Unrealized losses over 12 months	(2,276)
Fair value over 12 months	13,120
Total Unrealized losses	(7,111)	(123)
Total Fair value	63,557	17,470
Asset backed securities
Investment securities available-for-sale
Fair value less than 12 months	32
Fair value over 12 months	2	2
Total Fair value	34	2
Corporate bonds
Investment securities available-for-sale
Unrealized losses less than 12 months	(4,452)	(11)
Fair value less than 12 months	48,048	5,989
Unrealized losses over 12 months	(2,516)
Fair value over 12 months	14,484
Total Unrealized losses	(6,968)	(11)
Total Fair value	62,532	5,989
Obligations of state and political agencies.
Investment securities available-for-sale
Unrealized losses less than 12 months		(349)
Fair value less than 12 months		53,210
Total Unrealized losses		(349)
Total Fair value		$ 53,210
Held-to-maturity investment securities
Unrealized losses less than 12 months	(3,336)
Fair value less than 12 months	18,788
Unrealized losses over 12 months	(14,400)
Fair value over 12 months	98,762
Total Unrealized losses	(17,736)
Total Fair value	$ 117,550