Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 6. Income Taxes ASC 740, Income Taxes, defines the threshold for recognizing the benefits of tax return positions in the financial statements as "more-likely-than-not" to be sustained by the taxing authority. This section also provides guidance on the derecognition, measurement and classification of income tax uncertainties, along with any related interest and penalties, and includes guidance concerning accounting for income tax uncertainties in interim periods. The unrecognized tax benefit related to uncertain tax positions related to state income tax filings was $2.8 million at March 31, 2018 compared to $1.3 million at March 31, 2017. No change was recorded to the unrecognized tax benefit related to uncertain tax positions in each of the three month periods ended March 31, 2018 and 2017. Pinnacle Financial's policy is to recognize interest and/or penalties related to income tax matters in income tax expense. For the three months ended March 31, 2018 there were no interest and penalties recorded in the income statement compared to $18,000 in interest and penalties for the three months ended March 31, 2017. Pinnacle Financial's effective tax rate for the three months ended March 31, 2018 was 19.0% compared to 25.8% for the three months ended March 31, 2017. The difference between the effective tax rate and the federal and state income tax statutory rate of 26.14% at March 31, 2018 and 39.23% at March 31, 2017 is primarily due to the reduction in the statutory corporate tax rate following the enactment of the Tax Cuts and Jobs Act in December 2017, state excise tax expense, investments in bank qualified municipal securities, tax benefits of Pinnacle Financial's real estate investment trust subsidiary, participation in the Tennessee Community Investment Tax Credit (CITC) program, and tax benefits associated with share-based compensation, bank-owned life insurance and our captive insurance subsidiary, offset in part by the limitation on deductibility of meals and entertainment expense and FDIC premiums. Additionally, in March 2016, the FASB issued updated guidance to Accounting Standards Update, 2016-09 Stock Compensation Improvements to Employee Share-Based Payment Activity (ASU 2016-09) intended to simplify and improve several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of such awards as either equity or liabilities and classification of such awards on the statement of cash flows. This Accounting Standards Update (ASU) impacted Pinnacle Financial's consolidated financial statements by requiring that all income tax effects related to settlements of share-based payment awards be reported as increases (or decreases) to income tax expense. Previously, income tax benefits at settlement of an award were reported as an increase (or decrease) to additional paid-in capital. The ASU also requires that all income tax related cash flows resulting from share-based payments be reported as operating activities in the statement of cash flows whereas these cash flows were previously reported as a reduction to operating cash flows and an increase to financing cash flows. The guidance became effective for Pinnacle Financial on January 1, 2017. The impact of the adoption of ASU 2016-09 was included in income tax expense for the three months ended March 31, 2018 and 2017 resulting in the recognition of $2.7 million and $3.8 million, respectively, of tax benefits which reduced income tax expense.

Note 6. Income Taxes

ASC 740, Income Taxes, defines the threshold for recognizing the benefits of tax return positions in the financial statements as "more-likely-than-not" to be sustained by the taxing authority. This section also provides guidance on the derecognition, measurement and classification of income tax uncertainties, along with any related interest and penalties, and includes guidance concerning accounting for income tax uncertainties in interim periods.

The unrecognized tax benefit related to uncertain tax positions related to state income tax filings was $2.8 million at March 31, 2018 compared to $1.3 million at March 31, 2017. No change was recorded to the unrecognized tax benefit related to uncertain tax positions in each of the three month periods ended March 31, 2018 and 2017.

Pinnacle Financial's policy is to recognize interest and/or penalties related to income tax matters in income tax expense. For the three months ended March 31, 2018 there were no interest and penalties recorded in the income statement compared to $18,000 in interest and penalties for the three months ended March 31, 2017.

Pinnacle Financial's effective tax rate for the three months ended March 31, 2018 was 19.0% compared to 25.8% for the three months ended March 31, 2017. The difference between the effective tax rate and the federal and state income tax statutory rate of 26.14% at March 31, 2018 and 39.23% at March 31, 2017 is primarily due to the reduction in the statutory corporate tax rate following the enactment of the Tax Cuts and Jobs Act in December 2017, state excise tax expense, investments in bank qualified municipal securities, tax benefits of Pinnacle Financial's real estate investment trust subsidiary, participation in the Tennessee Community Investment Tax Credit (CITC) program, and tax benefits associated with share-based compensation, bank-owned life insurance and our captive insurance subsidiary, offset in part by the limitation on deductibility of meals and entertainment expense and FDIC premiums.

Additionally, in March 2016, the FASB issued updated guidance to Accounting Standards Update, 2016-09 Stock Compensation Improvements to Employee Share-Based Payment Activity (ASU 2016-09) intended to simplify and improve several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of such awards as either equity or liabilities and classification of such awards on the statement of cash flows. This Accounting Standards Update (ASU) impacted Pinnacle Financial's consolidated financial statements by requiring that all income tax effects related to settlements of share-based payment awards be reported as increases (or decreases) to income tax expense. Previously, income tax benefits at settlement of an award were reported as an increase (or decrease) to additional paid-in capital. The ASU also requires that all income tax related cash flows resulting from share-based payments be reported as operating activities in the statement of cash flows whereas these cash flows were previously reported as a reduction to operating cash flows and an increase to financing cash flows. The guidance became effective for Pinnacle Financial on January 1, 2017. The impact of the adoption of ASU 2016-09 was included in income tax expense for the three months ended March 31, 2018 and 2017 resulting in the recognition of $2.7 million and $3.8 million, respectively, of tax benefits which reduced income tax expense.