Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 12,833	$ 10,577	$ 35,755	$ 32,035
Other comprehensive income (loss), net of tax:
Securities available for sale and transferred securities	1,121	(1,736)	11,863	(10,493)
Hedging derivative instruments	43	85	(317)	208
Pension and post-retirement obligations	262	127	784	381
Total other comprehensive income (loss), net of tax	1,426	(1,524)	12,330	(9,904)
Comprehensive income	$ 14,259	$ 9,053	$ 48,085	$ 22,131