Investment Securities - Summary of Amortized Cost and Estimated Fair Value (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Securities available for sale
Amortized Cost	$ 301,854,000	$ 221,311,000
Unrealized Gains	1,872,000	2,758,000
Unrealized Losses	(3,310,000)	(1,030,000)
Fair Value (Estimated)	300,416,000	223,039,000
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	226,828,000	240,023,000
Unrealized Gains	2,973,000	5,545,000
Unrealized Losses	(4,264,000)	(2,445,000)
Fair Value (Estimated)	225,537,000	243,123,000
Restricted equity securities, cost and FMV [Abstract]
Amortized Cost	11,930,000	14,257,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value Estimated	11,930,000	14,257,000
Federal Home Loan Bank Stock
Restricted equity securities, cost and FMV [Abstract]
Amortized Cost	10,893,000	13,220,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value Estimated	10,893,000	13,220,000
Federal Reserve Bank Stock
Restricted equity securities, cost and FMV [Abstract]
Amortized Cost	1,037,000	1,037,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value Estimated	1,037,000	1,037,000
Mortgage-backed securities
Securities available for sale
Amortized Cost-Debt	282,397,000	194,563,000
Unrealized Gains	1,334,000	1,509,000
Unrealized Losses	(3,127,000)	(962,000)
Fair Value (Estimated)	280,604,000	195,110,000
State and political subdivisions
Securities available for sale
Amortized Cost-Debt	16,183,000	23,367,000
Unrealized Gains	475,000	1,201,000
Unrealized Losses	(176,000)	(62,000)
Fair Value (Estimated)	16,482,000	24,506,000
Other equity securities
Securities available for sale
Amortized Cost-Debt	3,274,000	3,381,000
Unrealized Gains	63,000	48,000
Unrealized Losses	(7,000)	(6,000)
Fair Value (Estimated)	3,330,000	3,423,000
U.S. Government-sponsored agencies
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	11,943,000	71,000,000
Unrealized Gains	35,000	40,000
Unrealized Losses	(233,000)	(2,284,000)
Fair Value (Estimated)	11,745,000	68,756,000
Mortgage-backed securities
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	31,201,000	42,193,000
Unrealized Gains	967,000	1,305,000
Unrealized Losses	(147,000)	(136,000)
Fair Value (Estimated)	32,021,000	43,362,000
State and political subdivisions
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	179,384,000	122,530,000
Unrealized Gains	1,971,000	4,200,000
Unrealized Losses	(3,884,000)	(25,000)
Fair Value (Estimated)	177,471,000	126,705,000
Corporate securities
Securities to be held to maturity, cost and FMV [Abstract]
Amortized Cost	4,300,000	4,300,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value (Estimated)	$ 4,300,000	$ 4,300,000

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