Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 29,992	$ 37,446	$ 52,130	$ 129,181
Securities available for sale:
Unrealized holding gains (losses) on securities	388	(62)	19,685	20,648
Reclassification adjustment for gains (losses) realized in net income	0	1,876	(23)	1,872
Total securities available for sale	388	1,814	19,662	22,520
Derivative instruments:
Unrealized holding gains (losses) on derivative instruments	1,175	(708)	(2,621)	(3,164)
Total derivative instruments	1,175	(708)	(2,621)	(3,164)
Defined benefit pension and post-retirement benefit plans:
Amortization of net actuarial loss recognized in net periodic pension cost	48	78	145	234
Total defined benefit pension and post-retirement benefit plans	48	78	145	234
Other comprehensive income, net of tax	1,611	1,184	17,186	19,590
Comprehensive income	$ 31,603	$ 38,630	$ 69,316	$ 148,771