Subordinated Debentures (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Mar. 14, 2014	Aug. 15, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 56,807	$ 56,807
Subordinated debentures held by trusts			$ 1,700
Conversion of subordinated debt into common stock (in shares)	287,852	1,200,000	0	287,852	1,176,470
Additional stock issued as an inducement (in shares)		25,060
Expense related to inducement					$ 400
EFSC Capital Trust VIII
Subordinated Borrowing [Line Items]
Trust preferred subordinated debentures	$ 5,000	$ 20,000
Conversion price (usd per share)	$ 17.37
Trust preferred securities [Member] | EFSC Clayco Statutory Trust I
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 3,196	$ 3,196
Maturity Date			Dec. 17, 2033
Call Date			Dec. 17, 2008
Description of variable rate			3 Month LIBOR
Floating interest rate			2.85%
Trust preferred securities [Member] | EFSC Capital Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 5,155	5,155
Maturity Date			Jun. 17, 2034
Call Date			Jun. 17, 2009
Description of variable rate			3 Month LIBOR
Floating interest rate			2.65%
Trust preferred securities [Member] | EFSC Statutory Trust III
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 11,341	11,341
Maturity Date			Dec. 15, 2034
Call Date			Dec. 15, 2009
Description of variable rate			3 Month LIBOR
Floating interest rate			1.97%
Trust preferred securities [Member] | EFSC Clayco Statutory Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 4,124	4,124
Maturity Date			Sep. 15, 2035
Call Date			Sep. 15, 2010
Description of variable rate			3 Month LIBOR
Floating interest rate			1.83%
Trust preferred securities [Member] | EFSC Statutory Trust IV
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 10,310	10,310
Maturity Date			Dec. 15, 2035
Call Date			Dec. 15, 2010
Description of variable rate			3 Month LIBOR
Floating interest rate			1.44%
Trust preferred securities [Member] | EFSC Statutory Trust V
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 4,124	4,124
Maturity Date			Sep. 15, 2036
Call Date			Sep. 15, 2011
Description of variable rate			3 Month LIBOR
Floating interest rate			1.60%
Trust preferred securities [Member] | EFSC Capital Trust VI
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 14,433	14,433
Maturity Date			Mar. 30, 2037
Call Date			Mar. 30, 2012
Description of variable rate			3 Month LIBOR
Floating interest rate			1.60%
Trust preferred securities [Member] | EFSC Capital Trust VII
Subordinated Borrowing [Line Items]
Subordinated debentures			$ 4,124	$ 4,124
Maturity Date			Dec. 15, 2037
Call Date			Dec. 15, 2012
Description of variable rate			3 Month LIBOR
Floating interest rate			2.25%
Trust preferred securities [Member] | EFSC Capital Trust VIII
Subordinated Borrowing [Line Items]
Fixed interest rate			9.00%