AFS Securities (Amortized cost and fair value of AFS securities, with gross unrealized gains and losses) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 512,869	$ 547,912
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,366	5,036
Gross Unrealized Gains	13,096	4,218
AFS securities	501,139	548,730
Government sponsored enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	184	217
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Gross Unrealized Gains	4	1
AFS securities	180	216
States and political subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	193,195	204,131
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,328	4,486
Gross Unrealized Gains	566	143
AFS securities	193,957	208,474
Auction rate money market preferred [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,200	3,200
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Gross Unrealized Gains	92	151
AFS securities	3,108	3,049
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	196,194	210,757
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	21	390
Gross Unrealized Gains	8,079	2,350
AFS securities	188,136	208,797
Collateralized mortgage obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	120,096	129,607
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	17	160
Gross Unrealized Gains	4,355	1,573
AFS securities	$ 115,758	$ 128,194

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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