CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 47,315	$ 28,628
Other comprehensive (loss) income, net of tax
Unrealized gain (loss) on debt securities arising during the period	(30,968)	(1,863)
Change in retirement obligation	405	328
Other comprehensive income (loss)	(30,563)	(1,535)
Comprehensive income	$ 16,752	$ 27,093