Investment Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 350,029	$ 346,078
Gross unrealized gains	4,484	4,363
Gross unrealized losses	(1,075)	(1,510)
Estimated fair value	353,438	348,931
U. S. treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,517	6,530
Gross unrealized gains	1	1
Gross unrealized losses	(1)	(1)
Estimated fair value	6,517	6,530
Common stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	580	588
Gross unrealized gains	906	695
Gross unrealized losses	0	0
Estimated fair value	1,486	1,283
U. S. federal agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	30,064	25,983
Gross unrealized gains	43	34
Gross unrealized losses	(187)	(274)
Estimated fair value	29,920	25,743
Municipal obligations, tax exempt [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	135,341	108,752
Gross unrealized gains	2,671	1,937
Gross unrealized losses	(71)	(180)
Estimated fair value	137,941	110,509
Municipal obligations, taxable [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	81,999	63,728
Gross unrealized gains	472	544
Gross unrealized losses	(581)	(350)
Estimated fair value	81,890	63,922
Agency mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	85,829	135,072
Gross unrealized gains	391	1,152
Gross unrealized losses	(235)	(705)
Estimated fair value	85,985	135,519
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	9,699	5,425
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	$ 9,699	$ 5,425