Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income		$ 41,711	$ 26,751
Other comprehensive income, net of tax
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax		(7,774)	9,347
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax		(6,583)	22,984
Net change in other comprehensive income for defined benefit postretirement plans	[1]	819	(772)
Total other comprehensive income (loss)		(13,538)	31,559
Total comprehensive income		$ 28,173	$ 58,310

[1] The amortization of prior service costs is included in the computation of net periodic pension cost as disclosed in Note 15 "Employee Benefit Plans" within the Notes to the Consolidated Financial Statements included in Item 8 of the Company's 2020 Form 10-K.