Preferred Stock and Common Stock Warrants	12 Months Ended
Dec. 31, 2011
NOTE 4—PREFERRED STOCK AND COMMON STOCK WARRANTS [Abstract]
Preferred stock and common stock warrants [Text Block]	PREFERRED STOCK AND COMMON STOCK WARRANTS On December 19, 2008, the Company entered into an agreement with the United States Department of the Treasury (“U.S. Treasury”) under the Capital Purchase Program, pursuant to which the Company sold (i) 35,000 shares of Fixed Rate Cumulative Perpetual Preferred Stock, Series A (“Senior Preferred Stock”) and (ii) a warrant to purchase 324,074 shares of EFSC common stock (“common stock warrants”), par value $0.01 per share, for an aggregate investment by the U.S. Treasury of $35.0 million. The proceeds received were allocated between the Senior Preferred Stock and the common stock warrants based upon their relative fair values, which resulted in the recording of a discount on the senior preferred stock upon issuance that reflects the value allocated to the warrants. The discount is being accreted using a level-yield basis over five years, consistent with management's estimate of the life of the preferred stock. The allocated carrying value of the Senior Preferred Stock and common stock warrants on the date of issuance (based on their relative fair values) were $31.1 million and $3.9 million, respectively. Cumulative dividends on the Senior Preferred Stock are payable at 5% per annum for the first five years and at a rate of 9% per annum thereafter on the liquidation preference of $1,000 per share. The Company is prohibited from paying any dividend with respect to shares of common stock unless all accrued and unpaid dividends are paid in full on the Senior Preferred Stock for all past dividend periods. The Senior Preferred Stock is non-voting, other than class voting rights on matters that could adversely affect the Senior Preferred Stock. The Senior Preferred Stock is callable at par after three years. Prior to the end of three years, according to the terms of the operative agreements, the Senior Preferred Stock may be redeemed with the proceeds from one or more qualified equity offerings of any Tier 1 perpetual preferred or common stock of EFSC of at least $8.8 million (each a “Qualified Equity Offering”), although certain amendments to the Emergency Economic Stabilization Act of 2008 enacted in February of 2009 eliminate this restriction on the means of redeeming the Senior Preferred Stock. The U.S. Treasury may also transfer the Senior Preferred Stock to a third party at any time. Common Stock Warrants The common stock warrants have a term of 10 years and are exercisable at any time, in whole or in part, at an exercise price of $16.20 per share (subject to certain anti-dilution adjustments). Assumptions were used in estimating the fair value of common stock warrants. The weighted average expected life of the common stock warrant represents the period of time that common stock warrants are expected to be outstanding. The risk-free interest rate was based on the U.S. Treasury yield curve in effect at the time of grant. The expected volatility was based on the historical volatility of the Company's stock. The following assumptions were used in estimating the fair value for the common stock warrants: a weighted average expected life of 10 years, a risk-free interest rate of 3.1%, an expected volatility of 47.3%, and a dividend yield of 5%. Based on these assumptions, the estimated fair value of the common stock warrants was $3.0 million. As previously noted, based on the common stock warrants' fair value relative to the senior preferred stock fair value, $3.9 million of the $35.0 million of proceeds was recorded to Additional paid in capital in the December 31, 2011 and 2010 consolidated balance sheets.

PREFERRED STOCK AND COMMON STOCK WARRANTS

On December 19, 2008, the Company entered into an agreement with the United States Department of the Treasury (“U.S. Treasury”) under the Capital Purchase Program, pursuant to which the Company sold (i) 35,000 shares of Fixed Rate Cumulative Perpetual Preferred Stock, Series A (“Senior Preferred Stock”) and (ii) a warrant to purchase 324,074 shares of EFSC common stock (“common stock warrants”), par value $0.01 per share, for an aggregate investment by the U.S. Treasury of $35.0 million.

The proceeds received were allocated between the Senior Preferred Stock and the common stock warrants based upon their relative fair values, which resulted in the recording of a discount on the senior preferred stock upon issuance that reflects the value allocated to the warrants. The discount is being accreted using a level-yield basis over five years, consistent with management's estimate of the life of the preferred stock. The allocated carrying value of the Senior Preferred Stock and common stock warrants on the date of issuance (based on their relative fair values) were $31.1 million and $3.9 million, respectively. Cumulative dividends on the Senior Preferred Stock are payable at 5% per annum for the first five years and at a rate of 9% per annum thereafter on the liquidation preference of $1,000 per share.

The Company is prohibited from paying any dividend with respect to shares of common stock unless all accrued and unpaid dividends are paid in full on the Senior Preferred Stock for all past dividend periods. The Senior Preferred Stock is non-voting, other than class voting rights on matters that could adversely affect the Senior Preferred Stock. The Senior Preferred Stock is callable at par after three years. Prior to the end of three years, according to the terms of the operative agreements, the Senior Preferred Stock may be redeemed with the proceeds from one or more qualified equity offerings of any Tier 1 perpetual preferred or common stock of EFSC of at least $8.8 million (each a “Qualified Equity Offering”), although certain amendments to the Emergency Economic Stabilization Act of 2008 enacted in February of 2009 eliminate this restriction on the means of redeeming the Senior Preferred Stock. The U.S. Treasury may also transfer the Senior Preferred Stock to a third party at any time.

Common Stock Warrants

The common stock warrants have a term of 10 years and are exercisable at any time, in whole or in part, at an exercise price of $16.20 per share (subject to certain anti-dilution adjustments). Assumptions were used in estimating the fair value of common stock warrants. The weighted average expected life of the common stock warrant represents the period of time that common stock warrants are expected to be outstanding. The risk-free interest rate was based on the U.S. Treasury yield curve in effect at the time of grant. The expected volatility was based on the historical volatility of the Company's stock. The following assumptions were used in estimating the fair value for the common stock warrants: a weighted average expected life of 10 years, a risk-free interest rate of 3.1%, an expected volatility of 47.3%, and a dividend yield of 5%. Based on these assumptions, the estimated fair value of the common stock warrants was $3.0 million. As previously noted, based on the common stock warrants' fair value relative to the senior preferred stock fair value, $3.9 million of the $35.0 million of proceeds was recorded to Additional paid in capital in the December 31, 2011 and 2010 consolidated balance sheets.