Acquisitions Acquisitions (Narrative)(Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 01, 2017	Oct. 01, 2016	Jun. 01, 2016	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Business Acquisition [Line Items]
Goodwill				$ 15,464		$ 10,990
HIghland County Bankshares Inc and Subsidiary First and Citizens Bank [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets							$ 123,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities							$ 107,000
First Century Bankshares, Inc [Member]
Business Acquisition [Line Items]
Business Acquisition, Combination Of Equity And Cash, Cash			35.00%
Business Acquisition, Combination Of Equity And Cash, Common Stock			65.00%
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Acquisition, Share Price			$ 22.50
Business Acquisition, Share Price, Number Of Shares	1,537,912		1.2433
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 406,154				$ 406,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	360,942				$ 361,000
Goodwill	4,440
Cash Consideration [Domain] | HIghland County Bankshares Inc and Subsidiary First and Citizens Bank [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 21,800
Cash Consideration [Domain] | First Century Bankshares, Inc [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	15,000
Stock Consideration [Domain] | First Century Bankshares, Inc [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 33,100
Core Deposits [Member] | First Century Bankshares, Inc [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	15 years