Basis of Presentation (Policies)	9 Months Ended
Sep. 30, 2019
Accounting Policies [Abstract]
Principles of Consolidation	All significant intercompany balances and transactions have been eliminated in consolidation.
Reclassification	Certain amounts reported in prior periods have been reclassified to conform to the current period presentation.
Recent Accounting Pronouncements	RECENT ACCOUNTING PRONOUNCEMENTS Pronouncements adopted during the nine months ended September 30, 2019: ASU No. 2016-02, ASU No. 2018-11, ASU No. 2018-20, and ASU 2019-01 In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842) which requires lessees to recognize ROU assets and lease liabilities on the balance sheet for most leases, including operating leases. The lessor accounting model was relatively unchanged by this ASU. Additional quantitative and qualitative disclosures are also required. During 2018 and early 2019, the FASB issued ASU No. 2018-11, Targeted Improvements, ASU No. 2018-20, Narrow-Scope Improvements for Lessors, and ASU No. 2019-01, Codification Improvements, which clarified certain implementation issues, provided an additional optional transition method and clarified the disclosure requirements during the period of adopting ASC 842, among others. The Company adopted ASU No. 2016-02 and the related ASUs discussed above effective January 1, 2019 using the optional transition method. The Company elected the package of practical expedients that does not require the reassessment of whether expired or existing contracts contain leases, the reassessment of the lease classification for any expired or existing leases, or the reassessment of initial direct costs for existing leases. Additionally, the Company did not elect the hindsight practical expedient. The Company conducted a review of all existing lease contracts and service contracts which might contain embedded leases. Some of the Company’s leases contain variable lease payments, the majority of which depend on an index or rate, such as the Consumer Price Index. At transition, the present value of variable payments was based on the index or rate as of January 1, 2019. To determine the present value of lease payments at transition, the Company applied a portfolio approach utilizing an FHLB Advance rate based on the weighted average remaining term of the Company’s existing leases as of January 1, 2019. As a result of adopting ASC 842, the Company established an ROU asset and a lease liability as of January 1, 2019 of $94.2 million and $118.9 million, respectively. Additionally, as part of the adoption of ASC 842, $24.7 million in pre-existing liabilities were reclassified to the ROU asset on January 1, 2019. This resulted in a gross-up of the balance sheet of $94.2 million as a result of recognizing lease liabilities and corresponding right-of-use assets for operating leases. The adoption of ASC 842 also required the recognition of previously deferred gains on sale-leaseback transactions which resulted in an insignificant increase to retained earnings on January 1, 2019. The related impact on the Company’s regulatory capital ratios was not significant. The Company does not expect material changes to the recognition of lease expense in future periods as a result of the adoption of ASC 842. See Note 8, Leases, for additional disclosures required by ASC 842. ASU No. 2018-16 In October 2018, the FASB released ASU No. 2018-16, Derivatives and Hedging (ASC 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes, which permits the use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under ASC 815 in addition to the interest rates on direct Treasury obligations of the UST, the LIBOR swap rate, the OIS Rate based on the Fed Funds Effective Rate, and the SIFMA Municipal Swap Rate. The required effective date of this ASU was dependent upon when an entity adopted the provisions of ASU No. 2017-12. The Company adopted ASU No. 2018-16 effective January 1, 2019 on a prospective basis for qualifying new or redesignated hedging relations as ASU No. 2017-12 had previously been adopted on January 1, 2018. The implementation of this ASU did not have a significant impact on the Company’s consolidated financial statements. ASU No. 2017-08 In March 2017, the FASB issued ASU No. 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities, which shortens the amortization period for callable debt securities held at a premium to the earliest call date instead of the maturity date. The amendments do not require an accounting change for securities held at a discount, which will continue to be amortized to the maturity date. The Company adopted ASU No. 2017-08 effective January 1, 2019. The adoption of the ASU did not have a material impact to the Company’s consolidated financial statements. Pronouncements issued but not yet adopted: ASU No. 2016-13, ASU No. 2019-04 (portion related to ASC 326), and ASU No. 2019-05 In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (ASC 326): Measurement of Credit Losses on Financial Instruments. The guidance introduces an impairment model that is based on expected credit losses (ECL), rather than incurred losses, to estimate credit losses on certain types of financial instruments such as loans and held-to-maturity securities, including certain off-balance sheet financial instruments such as loan commitments. The measurement of ECL should consider historical information, current information, and reasonable and supportable forecasts, including estimates of prepayments, over the contractual term. Financial instruments with similar risk characteristics must be grouped together when estimating ECL. The ASU also expands credit quality disclosures. Additionally, ASU No. 2016-13 amends the current AFS security impairment model for debt securities. The new model will require an estimate of ECL when the fair value is below the amortized cost of the asset. The credit-related impairment (and subsequent recoveries) are recognized as an allowance on the balance sheet with a corresponding adjustment to the income statement. Non-credit related losses will continue to be recognized through OCI. In addition, ASU No. 2016-13 provides for a simplified accounting model for purchased financial assets with a more-than-insignificant amount of credit deterioration since their origination. The initial estimate of expected credit losses would be recognized through an ALLL with an offset (i.e., increase) to the cost basis of the related financial asset at acquisition. ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods. This ASU will be applied through a modified-retrospective approach, resulting in a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. A prospective transition approach is required for debt securities for which OTTI had been recognized before the effective date. Amounts previously recognized in AOCI as of the date of adoption that relate to improvements in cash flows expected to be collected should continue to be accreted into income over the remaining life of the asset. Recoveries of amounts previously written off relating to improvements in cash flows after the date of adoption should be recorded in earnings when received. During 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Financial Instruments-Credit Losses (ASC 326), Derivatives and Hedging (ASC 815), and Financial Instruments (ASC 825), which clarified the scope of ASU No. 2016-13 and addressed various issues, including accrued interest receivable balances, recoveries, variable interest rates and prepayments, and ASU No. 2019-05, Financial Instruments-Credit Losses (Topic 326): Targeted Transition Relief, which clarified certain implementation issues. The effective date for the portion of ASU No. 2019-04 related to credit losses and ASU No. 2019-05 are the same as ASU No. 2016-13. The Company’s cross-function implementation team and engaged third-party consultants have jointly developed and continue to execute the project plan and provide implementation oversight. Significant progress has been made in implementation efforts, including model development and validation, fulfillment of additional data needs for new disclosure and reporting requirements, and drafting of accounting policies. In October 2019, user acceptance testing was completed and the Company began concurrent model runs. Implementation efforts will continue through the remainder of 2019, including continued process refinement, documentation enhancement, and finalization of the internal control framework. Based on a preliminary analysis performed in the third quarter of 2019 and forecasts of macroeconomic conditions and exposures as of September 30, 2019, the transition adjustment on January 1, 2020 is estimated to generate an ACL to loans ratio of 1.00% to 1.20%. The Company currently intends to use a blend of multiple economic forecasts to estimate expected credit losses over a one to two year reasonable and supportable forecast period and then revert to longer term historical loss experience to arrive at lifetime expected credit losses. The estimated increase in ACL is primarily due to required increases for residential mortgage and home equity loans to include the requirement to estimate lifetime expected credit losses and the remaining length of time to maturity for these loans as well as an increase in reserves on acquired non-impaired loans which had low reserve levels under the previous accounting guidance. While these ASUs are expected to increase ACL, they do not change the overall credit risk in the Company's loan and lease portfolios or the ultimate losses therein. The transition adjustment to increase ACL will primarily result in a decrease to shareholders' equity, net of income taxes, on January 1, 2020. The ultimate impact of the adoption of these ASUs will depend on the composition of the loan, lease and securities portfolios, finalization of credit loss models, and macroeconomic conditions and forecasts at the adoption date. ASU No. 2018-13 In August 2018, the FASB released ASU No. 2018-13, Fair Value Measurement (ASC 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The ASU will be effective for fiscal years beginning after December 15, 2019, including interim periods, with early adoption permitted. The Company is currently evaluating the impact of the ASU. While adoption of this ASU will result in changes to existing disclosures, it will not have an impact on the Company’s financial position or results of operations. ASU No. 2018-17 In October 2018, the FASB released ASU No. 2018-17, Consolidation (ASC 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which improves the consistency of the application of the variable interest entity (VIE) related party guidance for common control arrangements. This ASU requires reporting entities to consider indirect interests held through related parties under common control on a proportional basis rather than as the equivalent of a direct interest in its entirety (as currently required in GAAP) when determining whether a decision-making fee is a variable interest. ASU No. 2018-17 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The guidance will be applied retrospectively with a cumulative-effect adjustment to retained earnings at the beginning of the earliest period presented. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements. ASU No. 2019-04 In April 2019, the FASB released ASU No. 2019-04, Codification Improvements to Financial Instruments-Credit Losses (ASC 326), Derivatives and Hedging (ASC 815), and Financial Instruments (ASC 825). The amendments in the ASU improve the Codification by eliminating inconsistencies and providing clarifications. The amendments related to the credit losses standard are discussed above under ASU 2016-13. With respect to hedge accounting, the ASU addresses partial-term fair value hedges, fair value hedge basis adjustments, and certain transition requirements, among other things. For recognizing and measuring financial instruments, the ASU addresses the scope of the guidance, the requirement for re-measurement under ASC 820 when using the measurement alternative, certain disclosure requirements and which equity securities have to be re-measured at historical exchange rates. Since the Company early adopted the guidance in ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities in 2018, the amended hedge accounting guidance in ASU No. 2019-04 will be effective as of the beginning of the first annual reporting period beginning after April 25, 2019 with early adoption permitted on any date after the issuance of this ASU. The Company is currently evaluating the impact of the ASU on the Company’s consolidated financial statements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842) which requires lessees to recognize ROU assets and lease liabilities on the balance sheet for most leases, including operating leases. The lessor accounting model was relatively unchanged by this ASU. Additional quantitative and qualitative disclosures are also required. During 2018 and early 2019, the FASB issued ASU No. 2018-11, Targeted Improvements, ASU No. 2018-20, Narrow-Scope Improvements for Lessors, and ASU No. 2019-01, Codification Improvements, which clarified certain implementation issues, provided an additional optional transition method and clarified the disclosure requirements during the period of adopting ASC 842, among others.

The Company adopted ASU No. 2016-02 and the related ASUs discussed above effective January 1, 2019 using the optional transition method. The Company elected the package of practical expedients that does not require the reassessment of whether expired or existing contracts contain leases, the reassessment of the lease classification for any expired or existing leases, or the reassessment of initial direct costs for existing leases. Additionally, the Company did not elect the hindsight practical expedient.

The Company conducted a review of all existing lease contracts and service contracts which might contain embedded leases. Some of the Company’s leases contain variable lease payments, the majority of which depend on an index or rate, such as the Consumer Price Index. At transition, the present value of variable payments was based on the index or rate as of January 1, 2019. To determine the present value of lease payments at transition, the Company applied a portfolio approach utilizing an FHLB Advance rate based on the weighted average remaining term of the Company’s existing leases as of January 1, 2019. As a result of adopting ASC 842, the Company established an ROU asset and a lease liability as of January 1, 2019 of $94.2 million and $118.9 million, respectively. Additionally, as part of the adoption of ASC 842, $24.7 million in pre-existing liabilities were reclassified to the ROU asset on January 1, 2019. This resulted in a gross-up of the balance sheet of $94.2 million as a result of recognizing lease liabilities and corresponding right-of-use assets for operating leases. The adoption of ASC 842 also required the recognition of previously deferred gains on sale-leaseback transactions which resulted in an insignificant increase to retained earnings on January 1, 2019. The related impact on the Company’s regulatory capital ratios was not significant. The Company does not expect material changes to the recognition of lease expense in future periods as a result of the adoption of ASC 842. See Note 8, Leases, for additional disclosures required by ASC 842.

In October 2018, the FASB released ASU No. 2018-16, Derivatives and Hedging (ASC 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes, which permits the use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under ASC 815 in addition to the interest rates on direct Treasury obligations of the UST, the LIBOR swap rate, the OIS Rate based on the Fed Funds Effective Rate, and the SIFMA Municipal Swap Rate.

The required effective date of this ASU was dependent upon when an entity adopted the provisions of ASU No. 2017-12. The Company adopted ASU No. 2018-16 effective January 1, 2019 on a prospective basis for qualifying new or redesignated hedging relations as ASU No. 2017-12 had previously been adopted on January 1, 2018. The implementation of this ASU did not have a significant impact on the Company’s consolidated financial statements.

In March 2017, the FASB issued ASU No. 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities, which shortens the amortization period for callable debt securities held at a premium to the earliest call date instead of the maturity date. The amendments do not require an accounting change for securities held at a discount, which will continue to be amortized to the maturity date.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (ASC 326): Measurement of Credit Losses on Financial Instruments. The guidance introduces an impairment model that is based on expected credit losses (ECL), rather than incurred losses, to estimate credit losses on certain types of financial instruments such as loans and held-to-maturity securities, including certain off-balance sheet financial instruments such as loan commitments. The measurement of ECL should consider historical information, current information, and reasonable and supportable forecasts, including estimates of prepayments, over the contractual term. Financial instruments with similar risk characteristics must be grouped together when estimating ECL. The ASU also expands credit quality disclosures.

Additionally, ASU No. 2016-13 amends the current AFS security impairment model for debt securities. The new model will require an estimate of ECL when the fair value is below the amortized cost of the asset. The credit-related impairment (and subsequent recoveries) are recognized as an allowance on the balance sheet with a corresponding adjustment to the income statement. Non-credit related losses will continue to be recognized through OCI.

In addition, ASU No. 2016-13 provides for a simplified accounting model for purchased financial assets with a more-than-insignificant amount of credit deterioration since their origination. The initial estimate of expected credit losses would be recognized through an ALLL with an offset (i.e., increase) to the cost basis of the related financial asset at acquisition.

ASU No. 2016-13 will be effective for fiscal years beginning after December 15, 2019, including interim periods. This ASU will be applied through a modified-retrospective approach, resulting in a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. A prospective transition approach is required for debt securities for which OTTI had been recognized before the effective date. Amounts previously recognized in AOCI as of the date of adoption that relate to improvements in cash flows expected to be collected should continue to be accreted into income over the remaining life of the asset. Recoveries of amounts previously written off relating to improvements in cash flows after the date of adoption should be recorded in earnings when received.

During 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Financial Instruments-Credit Losses (ASC 326), Derivatives and Hedging (ASC 815), and Financial Instruments (ASC 825), which clarified the scope of ASU No. 2016-13 and addressed various issues, including accrued interest receivable balances, recoveries, variable interest rates and prepayments, and ASU No. 2019-05, Financial Instruments-Credit Losses (Topic 326): Targeted Transition Relief, which clarified certain implementation issues. The effective date for the portion of ASU No. 2019-04 related to credit losses and ASU No. 2019-05 are the same as ASU No. 2016-13.

The Company’s cross-function implementation team and engaged third-party consultants have jointly developed and continue to execute the project plan and provide implementation oversight. Significant progress has been made in implementation efforts, including model development and validation, fulfillment of additional data needs for new disclosure and reporting requirements, and drafting of accounting policies. In October 2019, user acceptance testing was completed and the Company began concurrent model runs. Implementation efforts will continue through the remainder of 2019, including continued process refinement, documentation enhancement, and finalization of the internal control framework.

Based on a preliminary analysis performed in the third quarter of 2019 and forecasts of macroeconomic conditions and exposures as of September 30, 2019, the transition adjustment on January 1, 2020 is estimated to generate an ACL to loans ratio of 1.00% to 1.20%. The Company currently intends to use a blend of multiple economic forecasts to estimate expected credit losses over a one to two year reasonable and supportable forecast period and then revert to longer term historical loss experience to arrive at lifetime expected credit losses. The estimated increase in ACL is primarily due to required increases for residential mortgage and home equity loans to include the requirement to estimate lifetime expected credit losses and the remaining length of time to maturity for these loans as well as an increase in reserves on acquired non-impaired loans which had low reserve levels under the previous accounting guidance.

While these ASUs are expected to increase ACL, they do not change the overall credit risk in the Company's loan and lease portfolios or the ultimate losses therein. The transition adjustment to increase ACL will primarily result in a decrease to shareholders' equity, net of income taxes, on January 1, 2020. The ultimate impact of the adoption of these ASUs will depend on the composition of the loan, lease and securities portfolios, finalization of credit loss models, and macroeconomic conditions and forecasts at the adoption date.

In August 2018, the FASB released ASU No. 2018-13, Fair Value Measurement (ASC 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The ASU will be effective for fiscal years beginning after December 15, 2019, including interim periods, with early adoption permitted.

In October 2018, the FASB released ASU No. 2018-17, Consolidation (ASC 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which improves the consistency of the application of the variable interest entity (VIE) related party guidance for common control arrangements. This ASU requires reporting entities to consider indirect interests held through related parties under common control on a proportional basis rather than as the equivalent of a direct interest in its entirety (as currently required in GAAP) when determining whether a decision-making fee is a variable interest. ASU No. 2018-17 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The guidance will be applied retrospectively with a cumulative-effect adjustment to retained earnings at the beginning of the earliest period presented.

In April 2019, the FASB released ASU No. 2019-04, Codification Improvements to Financial Instruments-Credit Losses (ASC 326), Derivatives and Hedging (ASC 815), and Financial Instruments (ASC 825). The amendments in the ASU improve the Codification by eliminating inconsistencies and providing clarifications. The amendments related to the credit losses standard are discussed above under ASU 2016-13.

With respect to hedge accounting, the ASU addresses partial-term fair value hedges, fair value hedge basis adjustments, and certain transition requirements, among other things. For recognizing and measuring financial instruments, the ASU addresses the scope of the guidance, the requirement for re-measurement under ASC 820 when using the measurement alternative, certain disclosure requirements and which equity securities have to be re-measured at historical exchange rates.

Since the Company early adopted the guidance in ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities in 2018, the amended hedge accounting guidance in ASU No. 2019-04 will be effective as of the beginning of the first annual reporting period beginning after April 25, 2019 with early adoption permitted on any date after the issuance of this ASU.