Stockholders' Equity - Schedule of Preferred Stock Transactions (Details) (USD $)	0 Months Ended				12 Months Ended
	Nov. 23, 2011	Sep. 22, 2011 letter	Sep. 09, 2011	Jun. 30, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Class of Stock [Line Items]
Number of new stock issued during the period (shares)			2,822,000
Proceeds received by the Trust in connection with the issuance of common securities to the Corporation						$ 21,165,000	$ 24,150,000
Gain on retirement of preferred stock				10,100,000
The number of Repurchase Letters the Corporation entered into with the Treasury		2
Preferred stock issued under Small Business Lending Fund						90,783,000
Cash			25,813,171
Proceeds from Issuance of Common Stock			21,165,000
Total redemption price of the Series B Preferred Stock		116,596,111			235,000	126,000	76,000
Repurchase of warrant, number of common shares available	991,453
Exercise price of warrant	17.55
The price paid to acquire the Warrant at a private auction conduction by the Treasury	367,500					368,000
Series B Preferred Stock
Class of Stock [Line Items]
Number of new stock issued during the period (shares)		90,782.94
Liquidation preference amount (per share)		$ 1,000
Proceeds received by the Trust in connection with the issuance of common securities to the Corporation		90,782,940
Lending incentive fee annual percentage		2.00%
Series B Preferred Stock minimum outstanding aggregate liquidation amount		25,000,000
The redemption price of the Series B Preferred Stock, as a percentage of the liquidation amount		100.00%
Preferred stock issued under Small Business Lending Fund		90,782,940
Series B Preferred Stock | Right To Appoint Representative As observer To Board Of Directors
Class of Stock [Line Items]
Series B Preferred stock, number of missed dividend payments		5
Series B Preferred Stock | Right To Designate Director To Board Of Directors
Class of Stock [Line Items]
Series B Preferred stock, number of missed dividend payments		6
The number of directors that can be designated to the Board of Directors by Series B Preferred Shareholders		2
Series B Preferred Stock | Initial Period
Class of Stock [Line Items]
Dividend rate of the Series B Preferred Stock		5.00%
Series B Preferred Stock | Divident Rate, Second Through Tenth Period | Minimum
Class of Stock [Line Items]
Dividend rate of the Series B Preferred Stock		1.00%
Series B Preferred Stock | Divident Rate, Second Through Tenth Period | Maximum
Class of Stock [Line Items]
Dividend rate of the Series B Preferred Stock		5.00%
Series B Preferred Stock | Eleventh Period Through Nineteeth Period Up To Four and One Half Year Anniversary Of Date Of Issuance | Minimum
Class of Stock [Line Items]
Dividend rate of the Series B Preferred Stock		1.00%
Series B Preferred Stock | Eleventh Period Through Nineteeth Period Up To Four and One Half Year Anniversary Of Date Of Issuance | Maximum
Class of Stock [Line Items]
Dividend rate of the Series B Preferred Stock		7.00%
Series B Preferred Stock | Dividend Rate, Period Subsequent To Four And One Half Year Anniversary Of Date Of Issuance
Class of Stock [Line Items]
Dividend rate of the Series B Preferred Stock		9.00%
United States Department of Treasury
Class of Stock [Line Items]
The number of common shares of the Corporation that can be purchased with the Warrant, held by the Treasury				991,453
United States Department of Treasury | Series A Preferred Stock
Class of Stock [Line Items]
Number of shares exchanged related to the Exchange Agreement with the U.S Treasury				46,400
Preferred Stock, outstanding		69,600		69,600
United States Department of Treasury | Trust Preferred Securities
Class of Stock [Line Items]
Preferred Stock, outstanding		46,400
First Merchant Capital Trust III | Fixed Rate Perpetual Junior Subordinated Debentures
Class of Stock [Line Items]
Junior Subordinated Debentures, Fixed Rate Perpetual, Series A, Amount				47,800,000
First Merchant Capital Trust III | Interest Rate, Through February 20, 2014 | Junior Subordinated Debt | Fixed Rate Perpetual Junior Subordinated Debentures
Class of Stock [Line Items]
Interest rate on senior notes				5.00%
First Merchant Capital Trust III | Interest Rate, Thereafter | Junior Subordinated Debt | Fixed Rate Perpetual Junior Subordinated Debentures
Class of Stock [Line Items]
Interest rate on senior notes				9.00%
First Merchant Capital Trust III | United States Department of Treasury
Class of Stock [Line Items]
Liquidation preference amount (per share)				$ 1,000
First Merchant Capital Trust III | United States Department of Treasury | Trust Preferred Securities
Class of Stock [Line Items]
Number of new stock issued during the period (shares)				46,400
First Merchant Capital Trust III | Parent Company | Common Stock
Class of Stock [Line Items]
Number of new stock issued during the period (shares)				1,435
Proceeds received by the Trust in connection with the issuance of common securities to the Corporation				$ 1,400,000