Other Comprehensive Income/Loss - Schedule of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Investment securities available-for sale:
Change in net unrealized gain during period, pre-tax	$ (1,812)	$ (3,430)	$ 15,553	$ 15,241
Change in net unrealized gain during period, tax expense (benefit)	(845)	(1,359)	6,135	5,963
Change in net unrealized gain during period, net of tax	(967)	(2,071)	9,418	9,278
Reclassification adjustment for gains included in net income, pre-tax	(771)	(225)	(778)	(312)
Reclassification adjustment for gains included in net income, tax expense (benefit)	(360)	(89)	(307)	(123)
Reclassification adjustment for gains included in net income, net of tax	(411)	(136)	(471)	(189)
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity, pre-tax	465	490	1,394	1,394
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity, tax expense (benefit)	217	209	550	549
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity, net of tax	248	281	844	845
Unrealized (gain) loss on derivatives, pre-tax	(658)	512	(1,095)	(2,490)
Unrealized (gain) loss on derivatives, tax expense (benefit)	(307)	195	(432)	(946)
Unrealized (gain) loss on derivatives, net of tax	(351)	317	(663)	(1,544)
Reclassification adjustment for derivatives net (gains) losses included in income	1,128	0	1,128	0
Reclassification adjustment for derivatives net (gains) losses included in income, tax expense (benefit)	526	0	445	0
Reclassification adjustment for derivatives net (gains) losses included in income, net of tax	602	0	683	0
Defined benefits post-retirement benefit plan:
Change in net actuarial (gain) loss, pre-tax	(176)	15	(1,090)	43
Change in net actuarial (gain) loss, tax expense (benefit)	(82)	6	(430)	17
Change in net actuarial (gain) loss, net of tax amount	(94)	9	(660)	26
Other comprehensive income, before tax	(1,824)	(2,638)	15,112	13,876
Total other comprehensive income, tax expense (benefit)	(851)	(1,038)	5,961	5,460
Total other comprehensive income, net of tax amount	$ (973)	$ (1,600)	$ 9,151	$ 8,416