Accumulated Other Comprehensive Income (Loss) - Summary of Changes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 850,509	$ 726,827	$ 634,923
Other comprehensive income before reclassifications	(9,797)	1,274
Amounts reclassified from accumulated other comprehensive income	(2,422)	(1,006)
Period change	(12,219)	268	4,780
Ending balance	901,657	850,509	726,827
Total
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(1,362)	(1,630)	(6,410)
Period change	(12,219)	268	4,780
Ending balance	(13,581)	(1,362)	(1,630)
Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	12,325	14,098
Other comprehensive income before reclassifications	(9,087)	(37)
Amounts reclassified from accumulated other comprehensive income	(2,203)	(1,736)
Period change	(11,290)	(1,773)
Ending balance	1,035	12,325	14,098
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,347)	(2,182)
Other comprehensive income before reclassifications	(240)	(1,093)
Amounts reclassified from accumulated other comprehensive income	813	928
Period change	573	(165)
Ending balance	(1,774)	(2,347)	(2,182)
Unrealized Gains (Losses) on Defined Benefit Plans
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(11,340)	(13,546)
Other comprehensive income before reclassifications	(470)	2,404
Amounts reclassified from accumulated other comprehensive income	(1,032)	(198)
Period change	(1,502)	2,206
Ending balance	$ (12,842)	$ (11,340)	$ (13,546)