Condensed Financial Information of First Commonwealth Financial Corporation (Parent Company Only) - Statements of Financial Condition (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets
Loans	$ 4,229,608	$ 4,137,517
Premises and equipment, net	67,940	68,970
Other assets	138,698	141,872
Total assets	6,214,861	5,995,390
Liabilities and Shareholders' Equity
Subordinated debentures payable	72,167	105,750
Shareholders' equity	711,697	746,007	758,543	749,777
Total liabilities and shareholders’ equity	6,214,861	5,995,390
Parent [Member]
Assets
Cash	8,370	19,493
Loans	27	30
Investment in subsidiaries	696,438	736,165
Investment in unconsolidated subsidiary trusts	2,182	3,291
Investment in Jointly-Owned Company	8,559	8,347
Premises and equipment, net	6,376	9,347
Recievable from subsidiaries	267	1,583
Dividends receivable from subsidiaries	1,319	1,205
Other assets	62,633	76,715
Total assets	786,171	856,176
Liabilities and Shareholders' Equity
Accrued expenses and other liabilities	2,307	4,419
Subordinated debentures payable	72,167	105,750
Shareholders' equity	711,697	746,007
Total liabilities and shareholders’ equity	$ 786,171	$ 856,176