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		$ 24,902	$ 30,628	$ 51,653	$ 65,853
Other comprehensive income, net of tax
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax		1,695	5,445	11,042	10,174
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax		197	8,590	23,181	11,875
Net change in other comprehensive income for defined benefit postretirement plans	[1]	225	40	(547)	80
Total other comprehensive income		2,117	14,075	33,676	22,129
Total comprehensive income		$ 27,019	$ 44,703	$ 85,329	$ 87,982

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