Subordinated Debentures (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 141,100	$ 118,156
Debt issuance costs	(940)	(1,005)
Total junior subordinated debentures
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	92,040	69,161
Total junior subordinated debentures | EFSC Clayco Statutory Trust I
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 3,196	3,196
Maturity Date	Dec. 17, 2033
Call Date	Dec. 17, 2008
Total junior subordinated debentures | EFSC Clayco Statutory Trust I | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0285
Total junior subordinated debentures | EFSC Capital Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 5,155	5,155
Maturity Date	Jun. 17, 2034
Call Date	Jun. 17, 2009
Total junior subordinated debentures | EFSC Capital Trust II | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0265
Total junior subordinated debentures | EFSC Statutory Trust III
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 11,341	11,341
Maturity Date	Dec. 15, 2034
Call Date	Dec. 15, 2009
Total junior subordinated debentures | EFSC Statutory Trust III | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0197
Total junior subordinated debentures | EFSC Clayco Statutory Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 4,124	4,124
Maturity Date	Sep. 15, 2035
Call Date	Sep. 15, 2010
Total junior subordinated debentures | EFSC Clayco Statutory Trust II | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0183
Total junior subordinated debentures | EFSC Statutory Trust IV
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 10,310	10,310
Maturity Date	Dec. 15, 2035
Call Date	Dec. 15, 2010
Total junior subordinated debentures | EFSC Statutory Trust IV | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0144
Total junior subordinated debentures | EFSC Statutory Trust V
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 4,124	4,124
Maturity Date	Sep. 15, 2036
Call Date	Sep. 15, 2011
Total junior subordinated debentures | EFSC Statutory Trust V | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.016
Total junior subordinated debentures | EFSC Capital Trust VI
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 14,433	14,433
Maturity Date	Mar. 30, 2037
Call Date	Mar. 30, 2012
Total junior subordinated debentures | EFSC Capital Trust VI | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.016
Total junior subordinated debentures | EFSC Capital Trust VII
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 4,124	4,124
Maturity Date	Dec. 15, 2037
Call Date	Dec. 15, 2012
Total junior subordinated debentures | EFSC Capital Trust VII | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0225
Total junior subordinated debentures | JEFFCO Stat Trust I
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 7,953	8,019
Maturity Date	Feb. 22, 2031
Call Date	Feb. 22, 2011
Fixed interest rate	10.20%
Total junior subordinated debentures | JEFFCO Stat Trust II
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 4,362	4,335
Maturity Date	Mar. 17, 2034
Call Date	Mar. 17, 2009
Total junior subordinated debentures | JEFFCO Stat Trust II | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Fixed interest rate	2.75%
Total junior subordinated debentures | Trinity Capital Trust III
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 5,172	0
Maturity Date	Sep. 08, 2034
Call Date	Sep. 08, 2009
Total junior subordinated debentures | Trinity Capital Trust III | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.027
Total junior subordinated debentures | Trinity Capital Trust IV
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 10,284	0
Maturity Date	Nov. 23, 2035
Call Date	Aug. 23, 2010
Fixed interest rate	6.88%
Total junior subordinated debentures | Trinity Capital Trust V
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 7,462	0
Maturity Date	Dec. 15, 2036
Call Date	Sep. 15, 2011
Total junior subordinated debentures | Trinity Capital Trust V | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.0165
Subordinated notes
Subordinated Borrowing [Line Items]
Subordinated debentures and notes (net of debt issuance cost of $940 and $1,005, respectively)	$ 50,000	50,000
Debt issuance costs	(940)	(1,005)
Total fixed-to-floating rate subordinated notes	$ 49,060	$ 48,995
Maturity Date	Nov. 01, 2026
Call Date	Nov. 01, 2021
Fixed interest rate	4.75%
Subordinated notes | 3 Month LIBOR
Subordinated Borrowing [Line Items]
Floating interest rate	0.03387
Junior subordinated debentures
Subordinated Borrowing [Line Items]
Par value	$ 26,800
Preliminary fair value	$ 22,800