Acquisitions (Narrative) (Details) $ / shares in Units, $ in Thousands				3 Months Ended
	Oct. 01, 2017 USD ($) $ / shares shares	Sep. 01, 2017 USD ($) shares	Mar. 03, 2017 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Shares issued pursuant to acquisition				$ 114,478
Goodwill				142,872	$ 231,681	$ 233,070
Total assets				4,441,846	5,641,527	5,547,037
Total deposits				3,629,170	4,495,708	4,406,955
Total loans				3,289,355	$ 4,113,785	$ 4,042,369
Carolina Bank [Member]
Business Acquisition [Line Items]
Payments for acquisition			$ 25,300
Shares issued pursuant to acquisition, shares | shares			3,799,471
Shares issued pursuant to acquisition			$ 114,478
Goodwill			$ 65,072
Payments for acquisition per share | $ / shares			$ 20.00
Merger share conversion ratio			1.002
Contribution of cash in total consideration			25.00%
Contribution of stock in total consideration			75.00%
Closing stock price | $ / shares			$ 30.13
Carolina Bank [Member] | Pre Merger [Member]
Business Acquisition [Line Items]
Merger Related Expenses				4,600
Merger Related Expenses net of tax				$ 3,100
Basic and Diluted | $ / shares				$ 0.12
Carolina Bank [Member] | Borrowings [Member]
Business Acquisition [Line Items]
Useful life of acquired intangible assets			18 years
Carolina Bank [Member] | Deposit Liabilities [Member]
Business Acquisition [Line Items]
Useful life of acquired intangible assets			5 years
Carolina Bank [Member] | Core Deposit Intangible [Member]
Business Acquisition [Line Items]
Useful life of acquired intangible assets			7 years
Bear Insurance [Member]
Business Acquisition [Line Items]
Total purchase price		$ 9,800
Payments for acquisition		$ 7,900
Shares issued pursuant to acquisition, shares | shares		13,374
Shares issued pursuant to acquisition		$ 400
Goodwill		5,300
Other amortizable intangible assets		3,900
Annual commission income		4,000
Earn-out liability		$ 1,200
Asheville Savings Bank [Member]
Business Acquisition [Line Items]
Payments for acquisition	$ 17,900
Shares issued pursuant to acquisition, shares | shares	4,920,061
Shares issued pursuant to acquisition	$ 169,300
Goodwill	$ 87,458
Payments for acquisition per share | $ / shares	$ 41.90
Merger share conversion ratio	1.44
Contribution of cash in total consideration	10.00%
Contribution of stock in total consideration	90.00%
Closing stock price | $ / shares	$ 34.41
Asheville Savings Bank [Member] | Deposit Liabilities [Member]
Business Acquisition [Line Items]
Useful life of acquired intangible assets	5 years
Asheville Savings Bank [Member] | Core Deposit Intangible [Member]
Business Acquisition [Line Items]
Useful life of acquired intangible assets	7 years