Acquisitions Acquisitions (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 28, 2020	Apr. 24, 2020	Jan. 01, 2020	Sep. 17, 2019	Sep. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Assets					$ 2,946,862	$ 2,403,492	[1]
Cornerstone Financial Services Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired			100.00%
Business Acquisition, Share Price				$ 5,700.00
Business Acquisition, Share Price, Number Of Shares			570,000	228
Business Acquisition Combination of Equity and Cash, Cash				50.00%
Business Acquisition Combination of Equity and Cash, Common Stock				50.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			$ 195,029			195,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			176,313			$ 176,000
Goodwill			10,820
MVB [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		$ 38,417
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		188,236
Goodwill		14,670
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits		195,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans		35,300
Purchase Price		$ 50,300
Number of days of average daily closing balance of deposits prior to closing		30 days
Percent multiplier used to calculate purchase price		8.00%
As Recorded By Summit [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 12,965	29,691
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		37,315	195,414
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		188,834	176,545
Goodwill		14,665	10,822
Winfirst [Member]
Business Acquisition [Line Items]
Assets					$ 146,000
Stock Consideration [Member] | Cornerstone Financial Services Inc. [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			15,400
Stock Consideration [Member] | As Recorded By Summit [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			15,441
Cash Consideration [Member] | Cornerstone Financial Services Inc. [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			14,300
Cash Consideration [Member] | As Recorded By Summit [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 12,965	$ 14,250
Cash Consideration [Member] | Winfirst [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 21,700
Core Deposits [Member] | Cornerstone Financial Services Inc. [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			10 years
Core Deposits [Member] | MVB [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		10 years

[1] Derived from audited consolidated financial statements