Consolidated Condensed Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (22,482)	$ 11,482
Other comprehensive income (loss):
Unrealized gains (losses) on securities available for sale	9,458	4,603
Income tax expense (benefit)	(1,985)	(968)
Net of tax amount	7,473	3,635
Change in unrealized gain/(loss) on postretirement benefit:
Reclassification adjustment for deferred tax on defined benefit postretirement medical plan		82
Net of tax amount		82
Total other comprehensive income (loss)	7,473	3,717
Comprehensive (loss) income	$ (15,009)	$ 15,199