Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The Corporation’s accompanying consolidated financial statements and these notes to the financial statements include subsidiaries in which the Corporation has a controlling financial interest. The Corporation owns and operates FNBPA, First National Trust Company, First National Investment Services Company, LLC, F.N.B. Investment Advisors, Inc., First National Insurance Agency, LLC, Regency, Bank Capital Services, LLC and F.N.B. Capital Corporation, LLC, and includes results for each of these entities in the accompanying consolidated financial statements. The accompanying consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly reflect the Corporation’s financial position and results of operations in accordance with U.S. generally accepted accounting principles (GAAP). All significant intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. Events occurring subsequent to the date of the balance sheet have been evaluated for potential recognition or disclosure in the consolidated financial statements through the date of the filing of the consolidated financial statements with the Securities and Exchange Commission (SEC). Certain information and note disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the SEC. The interim operating results are not necessarily indicative of operating results the Corporation expects for the full year. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Corporation’s Annual Report on Form 10-K filed with the SEC on February 26, 2016. Use of Estimates The accounting and reporting policies of the Corporation conform with GAAP. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could materially differ from those estimates. Material estimates that are particularly susceptible to significant changes include the allowance for credit losses, securities valuations, goodwill and other intangible assets, fair value measurements and income taxes. Business Combinations Business combinations are accounted for by applying the acquisition method in accordance with Accounting Standards Codification (ASC) 805, Business Combinations. Under the acquisition method, identifiable assets acquired and liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date are measured at their fair values as of that date, and are recognized separately from goodwill. Results of operations of the acquired entities are included in the consolidated statement of comprehensive income from the date of acquisition. Beginning in 2016, measurement-period adjustments are recorded in the period the adjustment is identified. Prior to this time, measurement-period adjustments were recorded retrospectively. Cloud Computing Arrangements Beginning in 2016, for new or materially modified contracts, the Corporation prospectively adopted new accounting principles to evaluate fees paid for cloud computing arrangements to determine if those arrangements include the purchase of or license to software that should be accounted for separately as internal-use software. If a contract includes the purchase or license to software that should be accounted for separately as internal-use software, the contract is amortized over the software’s identified useful life in amortization of intangibles. For contracts that do not include a software license, the contract is accounted for as a service contract with fees paid recorded in other non-interest expense. Stock Based Compensation The Corporation accounts for its stock based compensation awards in accordance with Accounting Standards Codification (ASC) 718, Compensation—Stock Compensation, which requires the measurement and recognition of compensation expense, based on estimated fair values, for all share-based awards, including stock options and restricted stock, made to employees and directors. ASC 718 requires companies to estimate the fair value of share-based awards on the date of grant. The value of the portion of the award that is ultimately expected to vest is recognized as expense in the Corporation’s consolidated statement of comprehensive income over the shorter of requisite service periods or the period through the date that the employee first becomes eligible to retire. Some of the Corporation’s plans contain performance targets that affect vesting and can be achieved after the requisite service period and accounted for as a performance condition. Beginning in 2016, the performance target is not reflected in the estimation of the award’s grant date fair value and compensation cost is recognized in the period in which it becomes probable that the performance condition will be achieved. Because share-based compensation expense is based on awards that are ultimately expected to vest, share-based compensation expense has been reduced to account for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Variable Interest Entities The Corporation has investments in certain partnerships and limited liability entities that qualify as variable interest entities (VIEs). These entities are evaluated on an on-going basis to determine whether they should be consolidated. Consolidation of a VIE is appropriate if a reporting entity holds a controlling financial interest in the VIE. The Corporation has determined that it does not hold a controlling financial interest in any of the VIEs and, therefore, the assets and liabilities of these entities are not consolidated into its financial statements. Instead, investments in these entities are accounted for under the equity method of accounting and are evaluated periodically for impairment. The recorded investment in these entities is reported in other assets on the consolidated balance sheets.

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The Corporation’s accompanying consolidated financial statements and these notes to the financial statements include subsidiaries in which the Corporation has a controlling financial interest. The Corporation owns and operates FNBPA, First National Trust Company, First National Investment Services Company, LLC, F.N.B. Investment Advisors, Inc., First National Insurance Agency, LLC, Regency, Bank Capital Services, LLC and F.N.B. Capital Corporation, LLC, and includes results for each of these entities in the accompanying consolidated financial statements.

The accompanying consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly reflect the Corporation’s financial position and results of operations in accordance with U.S. generally accepted accounting principles (GAAP). All significant intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. Events occurring subsequent to the date of the balance sheet have been evaluated for potential recognition or disclosure in the consolidated financial statements through the date of the filing of the consolidated financial statements with the Securities and Exchange Commission (SEC).

Certain information and note disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the SEC. The interim operating results are not necessarily indicative of operating results the Corporation expects for the full year. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Corporation’s Annual Report on Form 10-K filed with the SEC on February 26, 2016.

Use of Estimates

The accounting and reporting policies of the Corporation conform with GAAP. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could materially differ from those estimates. Material estimates that are particularly susceptible to significant changes include the allowance for credit losses, securities valuations, goodwill and other intangible assets, fair value measurements and income taxes.

Business Combinations

Business combinations are accounted for by applying the acquisition method in accordance with Accounting Standards Codification (ASC) 805, Business Combinations. Under the acquisition method, identifiable assets acquired and liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date are measured at their fair values as of that date, and are recognized separately from goodwill. Results of operations of the acquired entities are included in the consolidated statement of comprehensive income from the date of acquisition. Beginning in 2016, measurement-period adjustments are recorded in the period the adjustment is identified. Prior to this time, measurement-period adjustments were recorded retrospectively.

Cloud Computing Arrangements

Beginning in 2016, for new or materially modified contracts, the Corporation prospectively adopted new accounting principles to evaluate fees paid for cloud computing arrangements to determine if those arrangements include the purchase of or license to software that should be accounted for separately as internal-use software. If a contract includes the purchase or license to software that should be accounted for separately as internal-use software, the contract is amortized over the software’s identified useful life in amortization of intangibles. For contracts that do not include a software license, the contract is accounted for as a service contract with fees paid recorded in other non-interest expense.

Stock Based Compensation

The Corporation accounts for its stock based compensation awards in accordance with Accounting Standards Codification (ASC) 718, Compensation—Stock Compensation, which requires the measurement and recognition of compensation expense, based on estimated fair values, for all share-based awards, including stock options and restricted stock, made to employees and directors.

ASC 718 requires companies to estimate the fair value of share-based awards on the date of grant. The value of the portion of the award that is ultimately expected to vest is recognized as expense in the Corporation’s consolidated statement of comprehensive income over the shorter of requisite service periods or the period through the date that the employee first becomes eligible to retire. Some of the Corporation’s plans contain performance targets that affect vesting and can be achieved after the requisite service period and accounted for as a performance condition. Beginning in 2016, the performance target is not reflected in the estimation of the award’s grant date fair value and compensation cost is recognized in the period in which it becomes probable that the performance condition will be achieved.

Because share-based compensation expense is based on awards that are ultimately expected to vest, share-based compensation expense has been reduced to account for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

Variable Interest Entities

The Corporation has investments in certain partnerships and limited liability entities that qualify as variable interest entities (VIEs). These entities are evaluated on an on-going basis to determine whether they should be consolidated. Consolidation of a VIE is appropriate if a reporting entity holds a controlling financial interest in the VIE. The Corporation has determined that it does not hold a controlling financial interest in any of the VIEs and, therefore, the assets and liabilities of these entities are not consolidated into its financial statements. Instead, investments in these entities are accounted for under the equity method of accounting and are evaluated periodically for impairment. The recorded investment in these entities is reported in other assets on the consolidated balance sheets.