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	$ 59,590	$ 50,143	$ 44,453
Other comprehensive (loss) income, before tax (benefit) expense:
Unrealized holding (losses) gains on securities arising during the period	(6,304)	2,798	25,153
Less: reclassification adjustment for (gains) losses on securities included in net income	(617)	153	(550)
Unrealized holding (losses) gains on derivatives arising during the period	(479)	450	472
Reclassification adjustment for gains on derivatives included in net income	(70)	(49)	(10)
Unrealized gains (losses) for postretirement obligation:
Transition obligation	0	0	0
Net gain (loss)	331	(102)	(313)
Total other comprehensive (loss) income, before income tax (benefit) expense	(7,139)	3,250	24,752
Income tax (benefit) expense related to items of other comprehensive (loss) income	(2,498)	1,137	8,663
Comprehensive Income	$ 54,949	$ 52,256	$ 60,542