Other Comprehensive Income - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), pre-tax	$ 2,788	$ 4,349	$ 5,326	$ 2,710
Total other comprehensive income (loss), tax expense (benefit)	1,078	1,678	2,049	1,052
Other comprehensive income, net of tax	1,710	2,671	3,277	1,658
Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	2,258	6,029	8,573	4,066
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	873	2,312	3,313	1,561
Other comprehensive income (loss), before reclassifications, net of tax	1,385	3,717	5,260	2,505
Reclassification from AOCI, pre-tax	0	0	(1,186)	(96)
Reclassification from AOCI, tax expense (benefit)	0	0	(458)	(36)
Reclassification from AOCI, net of tax	0	0	(728)	(60)
Total other comprehensive income (loss), pre-tax	2,240	5,987	7,308	3,831
Total other comprehensive income (loss), tax expense (benefit)	866	2,296	2,825	1,472
Other comprehensive income, net of tax	1,374	3,691	4,483	2,359
Amortization of unrealized holding gains on securities transferred to the held to maturity category
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	(18)	(42)	(79)	(139)
Reclassification from AOCI, tax expense (benefit)	(7)	(16)	(30)	(53)
Reclassification from AOCI, net of tax	(11)	(26)	(49)	(86)
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before reclassifications, pre-tax	807	(1,752)	(1,959)	(1,437)
Other comprehensive income (loss) before reclassifications, tax expense (benefit)	312	(677)	(760)	(556)
Other comprehensive income (loss), before reclassifications, net of tax	495	(1,075)	(1,199)	(881)
Total other comprehensive income (loss), pre-tax	807	(1,752)	(1,959)	(1,437)
Total other comprehensive income (loss), tax expense (benefit)	312	(677)	(760)	(556)
Other comprehensive income, net of tax	495	(1,075)	(1,199)	(881)
Defined benefit Pension and Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	(383)		(383)
Reclassification from AOCI, tax expense (benefit)	(148)		(148)
Reclassification from AOCI, net of tax	(235)		(235)
Total other comprehensive income (loss), pre-tax	(259)	114	(23)	316
Total other comprehensive income (loss), tax expense (benefit)	(100)	59	(16)	136
Other comprehensive income, net of tax	(159)	55	(7)	180
Amortization of net actuarial loss recognized in net periodic pension cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, pre-tax	124	114	360	316
Reclassification from AOCI, tax expense (benefit)	48	59	132	136
Reclassification from AOCI, net of tax	$ 76	$ 55	$ 228	$ 180