CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/ (LOSS) - UNAUDITED - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 16,209	$ 20,746	$ 59,388	$ 96,744
Investments available-for-sale:
Net change in unrealized gains/ (losses) on investments available-for-sale	34,416	(23,730)	27,432	(16,555)
Related income tax (expense)/ benefit	(8,634)	5,873	(6,862)	4,045
Net investment gains reclassified into earnings	0	0	0	0
Related income tax expense	0	0	0	0
Net effect on other comprehensive income/ (loss)	25,782	(17,857)	20,570	(12,510)
Investments held-to-maturity:
Amortization of unrealized loss transferred from investments available-for-sale	401	451	1,137	1,314
Related income tax benefit	(90)	(127)	(277)	(347)
Net effect on other comprehensive income/ (loss)	311	324	860	967
Defined benefit pension plan:
Amortization of net loss	0	10,286	0	10,737
Related income tax benefit	0	(2,620)	0	(2,735)
Net effect on other comprehensive income/ (loss)	0	7,666	0	8,002
Total other comprehensive income/ (loss)	26,093	(9,867)	21,430	(3,541)
Comprehensive income	$ 42,302	$ 10,879	$ 80,818	$ 93,203