CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/ (LOSS) - UNAUDITED - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 51,253	$ 43,935
Investments available-for-sale:
Net change in unrealized gains/ (losses) on investments available-for-sale	20,784	(65,923)
Related income tax (expense)/ benefit	(5,294)	16,897
Net investment gains reclassified into earnings	0	(8)
Related income tax expense	0	2
Net effect on other comprehensive income/ (loss)	15,490	(49,032)
Investments held-to-maturity:
Net change in unrealized gains/ (losses)	405	(15,929)
Related income tax (expense)/ benefit	(103)	4,083
Net effect on other comprehensive income/ (loss)	302	(11,846)
Defined benefit pension plan:
Amortization of net loss	225	196
Related income tax benefit	(57)	(50)
Net effect on other comprehensive income/ (loss)	168	146
Total other comprehensive income/ (loss)	15,960	(60,732)
Comprehensive income/ (loss)	$ 67,213	$ (16,797)