CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 122,844	$ 166,299	$ 235,107
Investments available-for-sale:
Net change in unrealized gains/ (losses) on investments available-for-sale	34,167	(152,196)	(38,104)
Related income tax (expense)/ benefit	(8,823)	38,762	9,751
Net investment (gains)/ losses reclassified into earnings	0	345	(212)
Related income tax expense/ (benefit)	0	(88)	54
Net effect on other comprehensive income/ (loss)	25,344	(113,177)	(28,511)
Investments held-to-maturity:
Net change in unrealized loss	1,726	(14,003)	0
Related income tax expense/ (benefit)	(452)	3,567	0
Net effect on other comprehensive income/ (loss)	1,274	(10,436)	0
Defined benefit pension plan:
Net change in unrealized losses	10,737	294	1,687
Related income tax benefit	(2,735)	(93)	(420)
Net effect on other comprehensive income/ (loss)	8,002	201	1,267
Total other comprehensive income/ (loss)	34,620	(123,412)	(27,244)
Comprehensive income	$ 157,464	$ 42,887	$ 207,863