Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2016
Basis of Presentation	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 September 30, 2016 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	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 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 statements 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	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	Stock Based Compensation The Corporation accounts for its stock based compensation awards in accordance with ASC 718, Compensation—Stock Compensation, which requires the measurement and recognition of compensation expense, based on estimated fair values, for all stock-based awards, including stock options and restricted stock, made to employees and directors. ASC 718 requires companies to estimate the fair value of stock-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 statements 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 are accounted for as performance conditions. 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 stock-based compensation expense is based on awards that are ultimately expected to vest, stock-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	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.
Statement of Cash Flows	Statement of Cash Flows Accounting Standards Update (ASU or Update) 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force), adds or clarifies guidance on eight cash flow issues. The Update is effective the first quarter of 2018. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.
Credit Losses	Credit Losses ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, commonly referred to as “CECL,” replaces the current incurred loss impairment methodology with a methodology that reflects expected credit losses for most financial assets measured at amortized cost and certain other instruments, including loans, held-to-maturity debt securities, net investments in leases and off-balance sheet credit exposures. In addition, the Update will require the use of a modified available-for-sale debt security impairment model and eliminate the current accounting for purchased credit impaired loans and debt securities. The Update is effective the first quarter of 2020. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.
Revenue Recognition	Revenue Recognition ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, addresses certain issues in the guidance on assessing collectability, presentation of sales taxes, noncash consideration, and completed contracts and contract modifications at transition. ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, clarifies several aspects of identifying performance obligations and licensing implementation guidance including guidance that is expected to reduce the cost and complexity by eliminating the need to assess whether goods and services are performance obligations if they are immaterial in the context of the contract with the customer. ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), clarifies the guidance on principal versus agent considerations when another party is involved in providing goods and services to a customer. The guidance requires a company to determine whether it is required to provide the specific good or service itself or to arrange for that good or service to be provided by another party. ASU 2014-09, Revenue from Contracts with Customers (Topic 606), modifies the guidance used to recognize revenue from contracts with customers for transfers of goods and services and transfers of nonfinancial assets, unless those contracts are within the scope of other guidance. The guidance also requires new qualitative and quantitative disclosures about contract balances and performance obligations. The Update can be adopted using either the full retrospective method or modified retrospective method. The Corporation intends to use the modified retrospective approach when adopted. The guidance for these Revenue Recognition Updates is effective for annual periods beginning in the first quarter of 2018. Early application is permitted beginning in the first quarter of 2017. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.
Investments	Investments ASU 2016-07, Investments—Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting, eliminates the requirement for an investor to retrospectively apply the equity method when an investment that it had accounted for by another method qualifies for use of the equity method. The Update is effective in the first quarter of 2017 with prospective application. Early application is permitted. This Update is not expected to have a material effect on the Consolidated Financial Statements.
Derivative and Hedging Activities	Derivative and Hedging Activities ASU 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force), provides clarification that determination of whether an embedded contingent put or call option in a financial instrument is clearly and closely related to the debt host requires only an analysis of the four-step decision sequence described in ASC 815-15-25-42. The Update is effective in the first quarter of 2017 with modified retrospective application. Early application is permitted. If an entity is no longer required to bifurcate an embedded derivative as a result of this Update and elects fair value accounting, the effects should be reported as a cumulative-effect adjustment. This Update is not expected to have a material effect on the Consolidated Financial Statements. ASU 2016-05, Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships (a consensus of the Emerging Issues Task Force), clarifies that a change in counterparty to a derivative instrument that has been designated as a hedging instrument under Topic 815 does not, in and of itself, require dedesignation of that hedging relationship provided all other hedge accounting criteria continue to be met. The Update is effective in the first quarter of 2017 with either prospective or modified retrospective application. Early application is permitted. This Update is not expected to have a material effect on the Consolidated Financial Statements.
Extinguishments of Liabilities	Extinguishments of Liabilities ASU 2016-04, Liabilities—Extinguishments of Liabilities (Subtopic 405-20): Recognition of Breakage for Certain Prepaid Stored-Value Products (a consensus of the Emerging Issues Task Force), requires entities that sell prepaid stored-value products redeemable for goods, services or cash at third-party merchants to recognize breakage. The Update is effective in the first quarter of 2018 with either the modified retrospective method by means of a cumulative-effect adjustment to retained earnings or retrospective application. Early application is permitted. This Update is not expected to have a material effect on the Consolidated Financial Statements.
Leases	Leases ASU 2016-02, Leases (Topic 842), requires lessees to put most leases on their balance sheets but recognize expenses in the income statement similar to current accounting. In addition, the Update changes the guidance for sale-leaseback transactions, initial direct costs and lease executory costs for most entities. All entities will classify leases to determine how to recognize lease related revenue and expense. The Update is effective in the first quarter of 2019 with modified retrospective application including a number of optional practical expedients. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.
Financial Instruments - Recognition and Measurement	Financial Instruments – Recognition and Measurement ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, amends the presentation and accounting for certain financial instruments, including liabilities measured at fair value under the fair value option, and equity investments. The guidance also updates fair value presentation and disclosure requirements for financial instruments measured at amortized cost. The Update is effective in the first quarter of 2018 with a cumulative-effect adjustment as of the beginning of the fiscal year of adoption. Early application is prohibited except for the provision requiring the recognition of changes in fair value related to changes in an entity’s own credit risk in other comprehensive income for financial liabilities measured using the fair value option. This Update is not expected to have a material effect on the Consolidated Financial Statements.
ASU 2016-09 [Member]
Stock Based Compensation	Stock Based Compensation ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. The Update is effective in the first quarter of 2017 by an application method determined by the type of transaction impacted by the adoption. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2016

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 September 30, 2016 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

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

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 statements 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

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

Stock Based Compensation

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

ASC 718 requires companies to estimate the fair value of stock-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 statements 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 are accounted for as performance conditions. 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 stock-based compensation expense is based on awards that are ultimately expected to vest, stock-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

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.

Statement of Cash Flows

Statement of Cash Flows

Accounting Standards Update (ASU or Update) 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force), adds or clarifies guidance on eight cash flow issues. The Update is effective the first quarter of 2018. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.

Credit Losses

Credit Losses

ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, commonly referred to as “CECL,” replaces the current incurred loss impairment methodology with a methodology that reflects expected credit losses for most financial assets measured at amortized cost and certain other instruments, including loans, held-to-maturity debt securities, net investments in leases and off-balance sheet credit exposures. In addition, the Update will require the use of a modified available-for-sale debt security impairment model and eliminate the current accounting for purchased credit impaired loans and debt securities. The Update is effective the first quarter of 2020. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.

Revenue Recognition

Revenue Recognition

ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, addresses certain issues in the guidance on assessing collectability, presentation of sales taxes, noncash consideration, and completed contracts and contract modifications at transition.

ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, clarifies several aspects of identifying performance obligations and licensing implementation guidance including guidance that is expected to reduce the cost and complexity by eliminating the need to assess whether goods and services are performance obligations if they are immaterial in the context of the contract with the customer.

ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), clarifies the guidance on principal versus agent considerations when another party is involved in providing goods and services to a customer. The guidance requires a company to determine whether it is required to provide the specific good or service itself or to arrange for that good or service to be provided by another party.

ASU 2014-09, Revenue from Contracts with Customers (Topic 606), modifies the guidance used to recognize revenue from contracts with customers for transfers of goods and services and transfers of nonfinancial assets, unless those contracts are within the scope of other guidance. The guidance also requires new qualitative and quantitative disclosures about contract balances and performance obligations. The Update can be adopted using either the full retrospective method or modified retrospective method. The Corporation intends to use the modified retrospective approach when adopted.

The guidance for these Revenue Recognition Updates is effective for annual periods beginning in the first quarter of 2018. Early application is permitted beginning in the first quarter of 2017. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.

Investments

Investments

ASU 2016-07, Investments—Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting, eliminates the requirement for an investor to retrospectively apply the equity method when an investment that it had accounted for by another method qualifies for use of the equity method. The Update is effective in the first quarter of 2017 with prospective application. Early application is permitted. This Update is not expected to have a material effect on the Consolidated Financial Statements.

Derivative and Hedging Activities

Derivative and Hedging Activities

ASU 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force), provides clarification that determination of whether an embedded contingent put or call option in a financial instrument is clearly and closely related to the debt host requires only an analysis of the four-step decision sequence described in ASC 815-15-25-42. The Update is effective in the first quarter of 2017 with modified retrospective application. Early application is permitted. If an entity is no longer required to bifurcate an embedded derivative as a result of this Update and elects fair value accounting, the effects should be reported as a cumulative-effect adjustment. This Update is not expected to have a material effect on the Consolidated Financial Statements.

ASU 2016-05, Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships (a consensus of the Emerging Issues Task Force), clarifies that a change in counterparty to a derivative instrument that has been designated as a hedging instrument under Topic 815 does not, in and of itself, require dedesignation of that hedging relationship provided all other hedge accounting criteria continue to be met. The Update is effective in the first quarter of 2017 with either prospective or modified retrospective application. Early application is permitted. This Update is not expected to have a material effect on the Consolidated Financial Statements.

Extinguishments of Liabilities

Extinguishments of Liabilities

ASU 2016-04, Liabilities—Extinguishments of Liabilities (Subtopic 405-20): Recognition of Breakage for Certain Prepaid Stored-Value Products (a consensus of the Emerging Issues Task Force), requires entities that sell prepaid stored-value products redeemable for goods, services or cash at third-party merchants to recognize breakage. The Update is effective in the first quarter of 2018 with either the modified retrospective method by means of a cumulative-effect adjustment to retained earnings or retrospective application. Early application is permitted. This Update is not expected to have a material effect on the Consolidated Financial Statements.

Leases

Leases

ASU 2016-02, Leases (Topic 842), requires lessees to put most leases on their balance sheets but recognize expenses in the income statement similar to current accounting. In addition, the Update changes the guidance for sale-leaseback transactions, initial direct costs and lease executory costs for most entities. All entities will classify leases to determine how to recognize lease related revenue and expense. The Update is effective in the first quarter of 2019 with modified retrospective application including a number of optional practical expedients. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.

Financial Instruments - Recognition and Measurement

Financial Instruments – Recognition and Measurement

ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, amends the presentation and accounting for certain financial instruments, including liabilities measured at fair value under the fair value option, and equity investments. The guidance also updates fair value presentation and disclosure requirements for financial instruments measured at amortized cost. The Update is effective in the first quarter of 2018 with a cumulative-effect adjustment as of the beginning of the fiscal year of adoption. Early application is prohibited except for the provision requiring the recognition of changes in fair value related to changes in an entity’s own credit risk in other comprehensive income for financial liabilities measured using the fair value option. This Update is not expected to have a material effect on the Consolidated Financial Statements.

ASU 2016-09 [Member]

Stock Based Compensation

Stock Based Compensation

ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. The Update is effective in the first quarter of 2017 by an application method determined by the type of transaction impacted by the adoption. Early application is permitted. The Corporation is currently assessing the potential impact to its Consolidated Financial Statements.