Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 06, 2019
Entity Information [Line Items]
Entity Address, City or Town	Indiana
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15701
City Area Code	724
Local Phone Number	349-7220
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	FCF
Entity Registrant Name	FIRST COMMONWEALTH FINANCIAL CORP /PA/
Entity Central Index Key	0000712537
Entity File Number	001-11138
Entity Tax Identification Number	251428528
Entity Address, Address Line One	601 Philadelphia Street
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		98,499,937
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes