CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 69,829	$ 69,118	$ 68,432
Other comprehensive income (loss), net of tax:
Net change in fair value of available for sale debt securities	6,655	19,988	(9,228)
Net change in fair value of cash flow hedges	(654)	(984)	619
Net change in defined benefit plan obligations	(2,155)	(1,932)	3,810
Total other comprehensive income (loss), net of tax	3,846	17,072	(4,799)
Total comprehensive income	$ 73,675	$ 86,190	$ 63,633