Subordinated Debentures Schedule of Subordinated Debentures Outstanding (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Subordinated debentures	$ 177,619	$ 170,937
First Commonwealth Bank 2028 [Member]
Debt Instrument [Line Items]
Subordinated debentures	49,546	49,499
First Commonwealth Bank 2033 [Member]
Debt Instrument [Line Items]
Subordinated debentures	49,306	49,271
First Commonwealth Capital Trust II [Member]
Debt Instrument [Line Items]
Subordinated debentures	30,929	30,929
First Commonwealth Capital Trust III [Member]
Debt Instrument [Line Items]
Subordinated debentures	41,238	41,238
First Commonwealth Financial Corporation
Debt Instrument [Line Items]
Subordinated debentures	$ 6,600	$ 0