CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 235,107	$ 96,953	$ 116,433
Investments available-for-sale:
Net change in unrealized gains/ (losses) on investments available-for-sale	(38,104)	32,950	14,429
Related income tax expense/ (benefit)	9,751	(8,428)	(3,742)
Net investment gains reclassified into earnings	(212)	(467)	(77)
Related income tax expense	54	120	20
Net effect on other comprehensive income/ (loss)	(28,511)	24,175	10,630
Defined benefit pension plan:
Net change of unrealized (gain)/ loss	1,687	(1,542)	1,175
Related income tax expense/ (benefit)	(420)	404	(383)
Net effect on other comprehensive income/ (loss)	1,267	(1,138)	792
Total other comprehensive income/ (loss)	(27,244)	23,037	11,422
Comprehensive income	$ 207,863	$ 119,990	$ 127,855