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Fair Value (Recorded amount of assets and liabilities measured at fair value) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
AFS Securities
AFS securities	$ 547,762	$ 548,730
Available-for-sale Securities, Equity Securities	3,575	3,577
Fair value, total	570,684	568,554
Level 1 [Member]
AFS Securities
Fair value, total	$ 3,575	$ 3,577
Percent of assets and liabilities measured at fair value	0.63%	0.63%
Level 2 [Member]
AFS Securities
Fair value, total	$ 548,175	$ 549,021
Percent of assets and liabilities measured at fair value	96.06%	96.56%
Level 3 [Member]
AFS Securities
Fair value, total	$ 18,934	$ 15,956
Percent of assets and liabilities measured at fair value	3.31%	2.81%
Recurring items [Member]
AFS Securities
AFS securities	$ 547,762	$ 548,730
Available-for-sale Securities, Equity Securities	3,575	3,577
Derivative instruments	(413)	291
Recurring items [Member] | Government sponsored enterprises [Member]
AFS Securities
AFS securities	202	216
Recurring items [Member] | States and political subdivisions [Member]
AFS Securities
AFS securities	211,633	208,474
Recurring items [Member] | Auction rate money market preferred [Member]
AFS Securities
AFS securities	3,012	3,049
Recurring items [Member] | Mortgage-backed securities [Member]
AFS Securities
AFS securities	206,861	208,797
Recurring items [Member] | Collateralized mortgage obligations [Member]
AFS Securities
AFS securities	126,054	128,194
Recurring items [Member] | Level 1 [Member]
AFS Securities
AFS securities	0	0
Available-for-sale Securities, Equity Securities	3,575	3,577
Derivative instruments	0	0
Recurring items [Member] | Level 1 [Member] | Government sponsored enterprises [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 1 [Member] | States and political subdivisions [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 1 [Member] | Auction rate money market preferred [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 1 [Member] | Mortgage-backed securities [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 1 [Member] | Collateralized mortgage obligations [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 2 [Member]
AFS Securities
AFS securities	547,762	548,730
Available-for-sale Securities, Equity Securities	0	0
Derivative instruments	413	291
Recurring items [Member] | Level 2 [Member] | Government sponsored enterprises [Member]
AFS Securities
AFS securities	202	216
Recurring items [Member] | Level 2 [Member] | States and political subdivisions [Member]
AFS Securities
AFS securities	211,633	208,474
Recurring items [Member] | Level 2 [Member] | Auction rate money market preferred [Member]
AFS Securities
AFS securities	3,012	3,049
Recurring items [Member] | Level 2 [Member] | Mortgage-backed securities [Member]
AFS Securities
AFS securities	206,861	208,797
Recurring items [Member] | Level 2 [Member] | Collateralized mortgage obligations [Member]
AFS Securities
AFS securities	126,054	128,194
Recurring items [Member] | Level 3 [Member]
AFS Securities
AFS securities	0	0
Available-for-sale Securities, Equity Securities	0	0
Derivative instruments	0	0
Recurring items [Member] | Level 3 [Member] | Government sponsored enterprises [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 3 [Member] | States and political subdivisions [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 3 [Member] | Auction rate money market preferred [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 3 [Member] | Mortgage-backed securities [Member]
AFS Securities
AFS securities	0	0
Recurring items [Member] | Level 3 [Member] | Collateralized mortgage obligations [Member]
AFS Securities
AFS securities	0	0
Nonrecurring items [Member]
AFS Securities
Impaired loans (net of the allowance for loan losses)	18,934	15,956
Nonrecurring items [Member] | Level 1 [Member]
AFS Securities
Impaired loans (net of the allowance for loan losses)	0	0
Nonrecurring items [Member] | Level 2 [Member]
AFS Securities
Impaired loans (net of the allowance for loan losses)	0	0
Nonrecurring items [Member] | Level 3 [Member]
AFS Securities
Impaired loans (net of the allowance for loan losses)	$ 18,934	$ 15,956

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