Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 20,130	$ 46,625	$ 22,138	$ 91,735
Securities available for sale:
Unrealized holding gains on securities	2,603	9,393	19,297	20,710
Reclassification adjustment for (losses) gains realized in net income	(23)	6	(23)	(4)
Total securities available for sale	2,580	9,399	19,274	20,706
Derivative instruments:
Unrealized holding losses on derivative instruments	(793)	(1,541)	(3,796)	(2,456)
Total derivative instruments	(793)	(1,541)	(3,796)	(2,456)
Defined benefit pension and post-retirement benefit plans:
Amortization of net actuarial loss recognized in net periodic pension cost	51	102	97	156
Total defined benefit pension and post-retirement benefit plans	51	102	97	156
Other comprehensive income, net of tax	1,838	7,960	15,575	18,406
Comprehensive income	$ 21,968	$ 54,585	$ 37,713	$ 110,141