Cash and Due from Banks	12 Months Ended
	Dec. 31, 2020
Cash and Due from Banks [Abstract]
Cash and Due from Banks	Cash and Due from BanksRegulations of the Board of Governors of the Federal Reserve System impose uniform reserve requirements on all depository institutions with transaction accounts, such as checking accounts and NOW accounts. Reserves are maintained in the form of vault cash or balances held with the local Federal Reserve Bank. First Commonwealth Bank maintained average balances of $173.2 million during 2020 and $14.7 million during 2019 with the Federal Reserve Bank of Cleveland.