CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 45,925	$ 46,481	$ 43,465
Other comprehensive income (loss), net of tax:
Net change in fair value of securities available for sale	621	(7,876)	(3,171)
Net change in fair value of cash flow hedges	(52)	(257)	244
Net change in defined benefit plan obligation adjustment	(97)	(1,925)	2,037
Total other comprehensive income (loss), net of tax	472	(10,058)	(890)
Total comprehensive income	$ 46,397	$ 36,423	$ 42,575