CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - UNAUDITED - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 75,464	$ 9,987
Investments available-for-sale:
Net change in unrealized gains/ (losses) on investments available-for-sale	(28,855)	14,263
Related income tax expense/ (benefit)	7,377	(3,624)
Net investment gains reclassified into earnings	(58)	(169)
Related income tax expense	15	42
Net effect on other comprehensive income/ (loss)	(21,521)	10,512
Defined benefit pension plan:
Net change of unrealized loss	227	219
Related income tax benefit	(63)	(55)
Net effect on other comprehensive income/ (loss)	164	164
Total other comprehensive income/ (loss)	(21,357)	10,676
Comprehensive income	$ 54,107	$ 20,663