Other Comprehensive Income - (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Securities available for sale:
Unrealized holding gains on securities, pre tax	$ 5,060	$ 4,249
Amortization of unrealized holding gains on securities transferred to the held to maturity category, pre tax	(33)	(51)
Total securities available for sale, pre tax	5,027	4,198
Unrealized holding gains on securities, tax expense (benefit)	1,953	1,625
Amortization of unrealized holding gains on securities transferred to the held to maturity category, tax expense (benefit)	(13)	(19)
Total securities available for sale, tax expense (benefit)	1,940	1,606
Net change in unrealized holding gains on securities	3,107	2,624
Amortization of unrealized holding gains on securities transferred to the held to maturity category	(20)	(32)
Total securities	3,087	2,592
Derivative instruments:
Unrealized holding losses on derivative instruments, pre-tax	(2,062)	(1,084)
Total derivative instruments, pre-tax	(2,062)	(1,084)
Unrealized holding gains on derivatives, tax expense (benefit)	(796)	(415)
Total derivative instruments, tax expense (benefit)	(796)	(415)
Unrealized holding gains (losses) on derivative instruments	(1,266)	(669)
Totals derivative instruments	(1,266)	(669)
Defined benefit pension and post-retirement benefit plans:
Amortization of net actuarial loss recognized in net periodic pension cost, pre-tax	117	93
Total defined benefit pension and post-retirement benefit plans, pre-tax	117	93
Amortization of net actuarial loss recognized in net periodic pension cost, tax expense (benefit)	45	36
Total defined benefit pension and post-retirement benefit plans, tax expense (benefit)	45	36
Less amortization of net actuarial gain recognized in net periodic pension cost	72	57
Total defined benefit pension and post-retirement benefit plans	72	57
Total other comprehensive income, pre-tax	3,082	3,207
Total other comprehensive income, tax expense (benefit)	1,189	1,227
Other comprehensive income, net of tax	$ 1,893	$ 1,980