Business Combinations and Asset Acquisitions	12 Months Ended
Dec. 31, 2022
Business Combination and Asset Acquisition [Abstract]
Acquisition	AcquisitionOn August 30, 2022, we entered into an agreement and plan of merger to acquire Centric Financial Corporation (“Centric”) and its banking subsidiary, Centric Bank. Centric will contribute seven full-service banking offices and one loan production office in the Harrisburg, Philadelphia and Lancaster MSAs. The acquisition is an all-stock transaction and Centric shareholders were entitled to receive a fixed exchange ratio of 1.09 shares of First Commonwealth common stock for each Centric common stock. This merger was completed after close of business January 31, 2023 resulting in the issuance of 9,688,478 shares of common stock.

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-URI https://asc.fasb.org/topic&trid=2303972

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=128092470&loc=d3e4946-128472

Name:	us-gaap_BusinessCombinationDisclosureTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration