Subordinated Debentures (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares	Nov. 01, 2016 USD ($)
Subordinated Borrowing [Line Items]
Number of Unconsolidated Statutory Business Trusts	10
Investments trust preferred securities	$ 2,100
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, respectively)	118,156	$ 118,105
Debt issuance costs	$ (1,005)	$ (1,136)
Floating interest rate	125
Conversion of subordinated debt into common stock (in shares) | shares	0	0	0
Senior Subordinated Notes [Member]
Subordinated Borrowing [Line Items]
Senior Subordinated Notes				$ 50,000
Subordinated Notes, Redemption Price	100.00%
Trust preferred securities [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, respectively)	$ 69,161	$ 69,241
Trust preferred securities [Member] | EFSC Clayco Statutory Trust I
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.0285
Trust preferred securities [Member] | EFSC Capital Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.0265
Trust preferred securities [Member] | EFSC Statutory Trust III
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.0197
Trust preferred securities [Member] | EFSC Clayco Statutory Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.0183
Trust preferred securities [Member] | EFSC Statutory Trust IV
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.0144
Trust preferred securities [Member] | EFSC Statutory Trust V
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.016
Trust preferred securities [Member] | EFSC Capital Trust VI
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.016
Trust preferred securities [Member] | EFSC Capital Trust VII
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, 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	0.0225
Trust preferred securities [Member] | JEFFCO Stat Trust I [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, respectively)	$ 8,019	8,153
Maturity Date	Feb. 22, 2031
Call Date	Feb. 22, 2011
Fixed interest rate	10.20%
Trust preferred securities [Member] | EFSC Capital Trust VIII
Subordinated Borrowing [Line Items]
Fixed interest rate	9.00%
Trust preferred securities [Member] | JEFFCO Stat Trust II [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, respectively)	$ 4,335	4,281
Maturity Date	Mar. 17, 2034
Call Date	Mar. 17, 2009
Description of variable rate	3 Month LIBOR
Fixed interest rate	2.75%
Senior Subordinated Notes [Member]
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $1,005 and $1,136, respectively)	$ 50,000	50,000
Debt issuance costs	(1,005)	(1,136)
Subordinated notes, net of issuance costs	$ 48,995	$ 48,864
Maturity Date	Nov. 01, 2026
Call Date	Nov. 01, 2021
Floating interest rate	0.03387
Fixed interest rate	4.75%