Accumulated Other Comprehensive Income (Loss) (''AOCI'') - Amount Reclassified from AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Amount Reclassified from AOCI
Gains on sale of securities			$ 527
Interest income on taxable securities	$ 2,401	$ 1,670	8,004	$ 4,828
Income tax expense	(4,054)	(2,172)	(12,157)	(7,292)
Net income	6,765	3,459	20,166	12,074
Amount Reclassified from AOCI
Amount Reclassified from AOCI
Net of tax	(19)	(31)	284	(95)
Unrealized Gains on Available-for-Sale Securities and I/O Strips
Amount Reclassified from AOCI
Net of tax			306
Unrealized Gains on Available-for-Sale Securities and I/O Strips | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Gains on sale of securities			527
Income tax expense			(221)
Net income			306
Unamortized Unrealized Gain on Available-for-Sale Securities Reclassified to Held-to-Maturity
Amount Reclassified from AOCI
Net of tax	8	8	60	24
Unamortized Unrealized Gain on Available-for-Sale Securities Reclassified to Held-to-Maturity | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Interest income on taxable securities	13	13	103	41
Income tax expense	(5)	(5)	(43)	(17)
Net income	8	8	60	24
Defined Benefit Pension Plan Items
Amount Reclassified from AOCI
Net of tax	(27)	(39)	(82)	(119)
Defined Benefit Pension Plan Items | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Income before income tax	(47)	(68)	(141)	(204)
Income tax benefit	20	29	59	85
Net of tax	(27)	(39)	(82)	(119)
Prior transition obligation | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Income before income tax	13	28	39	84
Actuarial losses | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Income before income tax	$ (60)	$ (96)	$ (180)	$ (288)