Subordinated Debentures (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 shares	Nov. 01, 2021	Nov. 01, 2016 USD ($)
Subordinated Borrowing [Line Items]
Investments trust preferred securities	$ 1,700
Number of Unconsolidated Statutory Business Trusts	8
Subordinated debentures (net of debt issuance cost of $1,267 and $0, respectively)	$ 105,540	$ 56,807
Debt Issuance Cost	$ (1,267)	$ 0
Conversion of subordinated debt into common stock (in shares) | shares	0	0	287,852
Senior Subordinated Notes [Member]
Subordinated Borrowing [Line Items]
Junior Subordinated Notes					$ 50,000
Subordinated Notes, Redemption Price				100.00%
Trust preferred securities [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures (net of debt issuance cost of $1,267 and $0, respectively)	$ 56,807	$ 56,807
Trust preferred securities [Member] | EFSC Clayco Statutory Trust I
Subordinated Borrowing [Line Items]
Subordinated debentures (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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 (net of debt issuance cost of $1,267 and $0, respectively)	$ 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%
Senior Subordinated Notes [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures (net of debt issuance cost of $1,267 and $0, respectively)	$ 50,000	0
Debt Issuance Cost	(1,267)	0
Subordinated notes, net of issuance costs	$ 48,733	$ 0
Maturity Date	Nov. 01, 2026
Call Date	Nov. 01, 2021
Floating interest rate	3.387%
Fixed interest rate	4.75%