CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 28,628	$ 45,839
Other comprehensive (loss) income, net of tax
Unrealized gain (loss) on debt securities arising during the period	(1,863)	23,505
Change in retirement obligation	328	290
Unrealized gain (loss) on derivatives	0	72
Other comprehensive income (loss)	(1,535)	23,867
Comprehensive income	$ 27,093	$ 69,706