Borrowings - Narrative (Details) (USD $)						12 Months Ended					0 Months Ended
	Nov. 01, 2013 investor	Nov. 01, 2013 5% Senior Notes Due 2028	Nov. 01, 2013 6.75% Subordinated Notes Due 2028	Dec. 31, 2013 Subordinated Debentures and Term Loans	Dec. 31, 2012 Subordinated Debentures and Term Loans	Dec. 31, 2013 Subordinated Debt First Merchant Capital Trust II	Nov. 01, 2013 Subordinated Debt First Merchant Capital Trust II	Dec. 31, 2012 Subordinated Debt First Merchant Capital Trust II	Sep. 15, 2012 Subordinated Debt First Merchant Capital Trust II	Jul. 02, 2007 Subordinated Debt First Merchant Capital Trust II	Aug. 22, 2012 Junior Subordinated Debt CNBC Statutory Trust I	Mar. 02, 2003 Junior Subordinated Debt CNBC Statutory Trust I	Mar. 31, 2009 Senior Notes	Dec. 31, 2013 Revolving Credit Facility Line of Credit Bank Of America, N.A.	Nov. 01, 2013 Revolving Credit Facility Line of Credit Bank Of America, N.A.	Dec. 31, 2013 Term Loan Line of Credit Bank Of America, N.A.	Dec. 31, 2013 Subordinated Debt Line of Credit Bank Of America, N.A.
Debt Instrument [Line Items]
Total Debt				$ 126,807,000	$ 112,161,000
Debt face amount		5,000,000	65,000,000				70,000,000			56,702,000	4,124,000	4,124,000	79,000,000
Interest rate on notes		5.00%	6.75%			1.70%		1.87%	6.495%			10.20%	2.625%
Description of variable rate basis						three-month LIBOR
Basis spread on variable rate						1.56%
Line of credit maximum borrowing capacity														55,000,000	55,000,000	5,000,000	50,000,000
Private debt issuance, number of institutional investors	4
Amount due in the event of a default																$ 5,000,000
The default rate percentage (per annum) on debt instrument																3.00%
The redemption price of the debt, percentage											104.59%