Fair Value of Financial Instruments and Fair Value Measurements (Details 1) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Estimated fair value	$ 374,426	$ 353,438
Derivative financial instruments	553	797
Common stocks [Member]
Assets:
Estimated fair value	1,002	1,486
Fair Value, Measurements, Recurring [Member]
Assets:
Derivative financial instruments	553	797
Fair Value, Measurements, Recurring [Member] | Common stocks [Member]
Assets:
Estimated fair value	1,002	1,486
Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities [Member]
Assets:
Estimated fair value	92,869	85,985
U. S. federal agency obligations [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	27,349	29,920
Municipal obligations, tax exempt [Member]
Assets:
Estimated fair value	163,848	137,941
Municipal obligations, tax exempt [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	163,848	137,941
Municipal obligations, taxable [Member]
Assets:
Estimated fair value	73,628	81,890
Municipal obligations, taxable [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	73,628	81,890
U. S. treasury securities [Member]
Assets:
Estimated fair value	6,030	6,517
U. S. treasury securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	6,030	6,517
Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	9,700	9,699
Fair Value, Inputs, Level 1 [Member]
Assets:
Estimated fair value	7,032	8,003
Derivative financial instruments	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Derivative financial instruments	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Common stocks [Member]
Assets:
Estimated fair value	1,002	1,486
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | U. S. federal agency obligations [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Municipal obligations, tax exempt [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Municipal obligations, taxable [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | U. S. treasury securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	6,030	6,517
Fair Value, Inputs, Level 1 [Member] | Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Estimated fair value	367,394	345,435
Derivative financial instruments	553	797
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Derivative financial instruments	553	797
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Common stocks [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities [Member]
Assets:
Estimated fair value	92,869	85,985
Fair Value, Inputs, Level 2 [Member] | U. S. federal agency obligations [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	27,349	29,920
Fair Value, Inputs, Level 2 [Member] | Municipal obligations, tax exempt [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	163,848	137,941
Fair Value, Inputs, Level 2 [Member] | Municipal obligations, taxable [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	73,628	81,890
Fair Value, Inputs, Level 2 [Member] | U. S. treasury securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	9,700	9,699
Fair Value, Inputs, Level 3 [Member]
Assets:
Estimated fair value	0	0
Derivative financial instruments	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Derivative financial instruments	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Common stocks [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | U. S. federal agency obligations [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Municipal obligations, tax exempt [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Municipal obligations, taxable [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | U. S. treasury securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Certificates of deposit [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Estimated fair value	$ 0	$ 0