CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/ (LOSS) - UNAUDITED - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 43,935	$ 75,464
Investments available-for-sale:
Net change in unrealized losses on investments available-for-sale	(65,923)	(28,855)
Related income tax expense	16,897	7,377
Net investment gains reclassified into earnings	(8)	(58)
Related income tax expense	2	15
Net effect on other comprehensive loss	(49,032)	(21,521)
Investments held-to-maturity:
Net change in unrealized loss	(15,929)	0
Related income tax expense	4,083	0
Net effect on other comprehensive loss	(11,846)	0
Defined benefit pension plan:
Net change of unrealized loss	196	227
Related income tax benefit	(50)	(63)
Net effect on other comprehensive loss	146	164
Total other comprehensive loss	(60,732)	(21,357)
Comprehensive income/ (loss)	$ (16,797)	$ 54,107