CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 46,481	$ 43,465	$ 40,824
Other comprehensive (loss) income, net of tax:
Net change in fair value of securities available for sale	(7,876)	(3,171)	1,021
Net change in fair value of cash flow hedges	(257)	244	331
Net change in defined benefit plan obligation adjustment	(1,925)	2,037	(8,608)
Total other comprehensive (loss) income, net of tax	(10,058)	(890)	(7,256)
Total comprehensive income	$ 36,423	$ 42,575	$ 33,568