Basis of Presentation Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
New Accounting Pronouncements, Policy	Recent Accounting Standards Effective January 1, 2015, the Corporation adopted the Financial Accounting Standards Board's ("FASB") Accounting Standards Codification ("ASC") Update 2014-01, "Accounting for Investments in Qualified Affordable Housing Projects." ASC Update 2014-01 provides guidance on accounting for investments made by a reporting entity in flow-through limited liability entities that manage or invest in affordable housing projects that qualify for the low income housing tax credit. The Corporation has made certain investments in partnerships that generate tax credits under various federal programs which promote investment in low and moderate income housing and local economic development. The net income tax benefit associated with these investments, which consists of the amortization of the investments net of tax benefits, and the income tax credits earned on the investments recorded in income taxes on the consolidated income statements was $2.4 million and $2.8 million for the three months ended June 30, 2015 and 2014, respectively and $4.8 million and $5.3 million for the six months ended June 30, 2015 and 2014, respectively. As of June 30, 2015 and December 31, 2014, the Corporation’s tax credit investments, included in other assets on the consolidated balance sheets, totaled $156.8 million and $155.6 million, respectively. The adoption of this ASC update did not have a material impact on the Corporation's consolidated financial statements for the three or six months ended June 30, 2015 or 2014. In February 2015, the FASB issued ASC Update 2015-02, "Consolidation: Amendments to the Consolidation Analysis." ASC Update 2015-02 changes the way reporting enterprises evaluate whether: (a) they should consolidate limited partnerships and similar entities, (b) fees paid to a decision maker or service provider are variable interests in a variable interest entity ("VIE"), and (c) variable interests in a VIE held by related parties of the reporting enterprise require the reporting enterprise to consolidate the VIE. ASC Update 2015-02 is effective for public business entities' annual and interim reporting periods beginning after December 15, 2015, with earlier adoption permitted. The Corporation intends to adopt this standards update effective with its March 31, 2016 quarterly report on Form 10-Q, and does not expect the adoption of ASC Update 2015-02 to have a material impact on its consolidated financial statements. In April 2015, the FASB issued ASC Update 2015-03, "Interest - Imputation of Interest." ASC Update 2015-03 simplifies the presentation of debt issuances costs. Debt issuance costs related to a recognized debt liability will be presented on the balance sheet as a direct deduction from the debt liability, similar to the presentation of debt discounts. Under current U.S. GAAP, debt issuance costs are reported on the balance sheet as assets. The costs will continue to be amortized to interest expense using the effective interest method. ASC Update 2015-03 is effective for public business entities' annual and interim reporting periods beginning after December 15, 2015, with earlier adoption permitted. The Corporation intends to adopt this standards update effective with its March 31, 2016 quarterly report on Form 10-Q and does not expect the adoption of ASC Update 2015-03 to have a material impact on its consolidated financial statements. In April 2015, the FASB issued ASC Update 2015-05, "Customer's Accounting for Fees Paid in a Cloud Computing Arrangement." ASC Update 2015-05 provides explicit guidance to determine when a customer's fees paid in a cloud computing arrangement is for the acquisition of software licenses, services, or both. ASC Update 2015-05 is effective for public business entities' annual and interim reporting periods beginning after December 15, 2015, with earlier adoption permitted. The Corporation intends to adopt this standards update effective with its March 31, 2016 quarterly report on Form 10-Q and does not expect the adoption of ASC Update 2015-05 to have a material impact on its consolidated financial statements.

Recent Accounting Standards

Effective January 1, 2015, the Corporation adopted the Financial Accounting Standards Board's ("FASB") Accounting Standards Codification ("ASC") Update 2014-01, "Accounting for Investments in Qualified Affordable Housing Projects." ASC Update 2014-01 provides guidance on accounting for investments made by a reporting entity in flow-through limited liability entities that manage or invest in affordable housing projects that qualify for the low income housing tax credit. The Corporation has made certain investments in partnerships that generate tax credits under various federal programs which promote investment in low and moderate income housing and local economic development. The net income tax benefit associated with these investments, which consists of the amortization of the investments net of tax benefits, and the income tax credits earned on the investments recorded in income taxes on the consolidated income statements was $2.4 million and $2.8 million for the three months ended June 30, 2015 and 2014, respectively and $4.8 million and $5.3 million for the six months ended June 30, 2015 and 2014, respectively. As of June 30, 2015 and December 31, 2014, the Corporation’s tax credit investments, included in other assets on the consolidated balance sheets, totaled $156.8 million and $155.6 million, respectively. The adoption of this ASC update did not have a material impact on the Corporation's consolidated financial statements for the three or six months ended June 30, 2015 or 2014.

In February 2015, the FASB issued ASC Update 2015-02, "Consolidation: Amendments to the Consolidation Analysis." ASC Update 2015-02 changes the way reporting enterprises evaluate whether: (a) they should consolidate limited partnerships and similar entities, (b) fees paid to a decision maker or service provider are variable interests in a variable interest entity ("VIE"), and (c) variable interests in a VIE held by related parties of the reporting enterprise require the reporting enterprise to consolidate the VIE. ASC Update 2015-02 is effective for public business entities' annual and interim reporting periods beginning after December 15, 2015, with earlier adoption permitted. The Corporation intends to adopt this standards update effective with its March 31, 2016 quarterly report on Form 10-Q, and does not expect the adoption of ASC Update 2015-02 to have a material impact on its consolidated financial statements.

In April 2015, the FASB issued ASC Update 2015-03, "Interest - Imputation of Interest." ASC Update 2015-03 simplifies the presentation of debt issuances costs. Debt issuance costs related to a recognized debt liability will be presented on the balance sheet as a direct deduction from the debt liability, similar to the presentation of debt discounts. Under current U.S. GAAP, debt issuance costs are reported on the balance sheet as assets. The costs will continue to be amortized to interest expense using the effective interest method. ASC Update 2015-03 is effective for public business entities' annual and interim reporting periods beginning after December 15, 2015, with earlier adoption permitted. The Corporation intends to adopt this standards update effective with its March 31, 2016 quarterly report on Form 10-Q and does not expect the adoption of ASC Update 2015-03 to have a material impact on its consolidated financial statements.

In April 2015, the FASB issued ASC Update 2015-05, "Customer's Accounting for Fees Paid in a Cloud Computing Arrangement." ASC Update 2015-05 provides explicit guidance to determine when a customer's fees paid in a cloud computing arrangement is for the acquisition of software licenses, services, or both. ASC Update 2015-05 is effective for public business entities' annual and interim reporting periods beginning after December 15, 2015, with earlier adoption permitted. The Corporation intends to adopt this standards update effective with its March 31, 2016 quarterly report on Form 10-Q and does not expect the adoption of ASC Update 2015-05 to have a material impact on its consolidated financial statements.