Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income		$ 120,992	$ 121,167	$ 165,175
Other comprehensive income (loss), net of tax
Net change in fair value of securities available for sale		(22,922)	8,857	10,345
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax		(19,139)	16,797	10,331
Net change in other comprehensive income for defined benefit postretirement plans	[1]	3,549	(3,128)	(1,334)
Total other comprehensive income (loss)		(38,512)	22,526	19,342
Total comprehensive income		$ 82,480	$ 143,693	$ 184,517

[1] The amortization of prior service costs is included in the computation of net periodic pension costs as disclosed in Note 14 - Employee Benefit Plans within the Notes to the Consolidated Financial Statements in Item 8.